A value equal to the total volume flow divided by the cross-sectional area of the vascular bed.
The flow of BLOOD through or around an organ or region of the body.
A non-invasive technique using ultrasound for the measurement of cerebrovascular hemodynamics, particularly cerebral blood flow velocity and cerebral collateral flow. With a high-intensity, low-frequency pulse probe, the intracranial arteries may be studied transtemporally, transorbitally, or from below the foramen magnum.
The circulation of blood through the BLOOD VESSELS of the BRAIN.
The largest of the cerebral arteries. It trifurcates into temporal, frontal, and parietal branches supplying blood to most of the parenchyma of these lobes in the CEREBRAL CORTEX. These are the areas involved in motor, sensory, and speech activities.
Ultrasonography applying the Doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. (Stedman, 25th ed)
Artery originating from the internal carotid artery and distributing to the eye, orbit and adjacent facial structures.
The arterial blood vessels supplying the CEREBRUM.
Rhythmic, intermittent propagation of a fluid through a BLOOD VESSEL or piping system, in contrast to constant, smooth propagation, which produces laminar flow.
Ultrasonography applying the Doppler effect, with the superposition of flow information as colors on a gray scale in a real-time image. This type of ultrasonography is well-suited to identifying the location of high-velocity flow (such as in a stenosis) or of mapping the extent of flow in a certain region.
Ultrasonography applying the Doppler effect, with velocity detection combined with range discrimination. Short bursts of ultrasound are transmitted at regular intervals and the echoes are demodulated as they return.
The circulation of blood through the CORONARY VESSELS of the HEART.
The force that opposes the flow of BLOOD through a vascular bed. It is equal to the difference in BLOOD PRESSURE across the vascular bed divided by the CARDIAC OUTPUT.
A method of non-invasive, continuous measurement of MICROCIRCULATION. The technique is based on the values of the DOPPLER EFFECT of low-power laser light scattered randomly by static structures and moving tissue particulates.
The movement and the forces involved in the movement of the blood through the CARDIOVASCULAR SYSTEM.
Clinical manifestation consisting of a deficiency of carbon dioxide in arterial blood.
Three groups of arteries found in the eye which supply the iris, pupil, sclera, conjunctiva, and the muscles of the iris.
Central retinal artery and its branches. It arises from the ophthalmic artery, pierces the optic nerve and runs through its center, enters the eye through the porus opticus and branches to supply the retina.
Measurement of intracardiac blood flow using an M-mode and/or two-dimensional (2-D) echocardiogram while simultaneously recording the spectrum of the audible Doppler signal (e.g., velocity, direction, amplitude, intensity, timing) reflected from the moving column of red blood cells.
Use of reflected ultrasound in the diagnosis of intracranial pathologic processes.
The study of the deformation and flow of matter, usually liquids or fluids, and of the plastic flow of solids. The concept covers consistency, dilatancy, liquefaction, resistance to flow, shearing, thixotrophy, and VISCOSITY.
Specialized arterial vessels in the umbilical cord. They carry waste and deoxygenated blood from the FETUS to the mother via the PLACENTA. In humans, there are usually two umbilical arteries but sometimes one.
A pulmonary ventilation rate faster than is metabolically necessary for the exchange of gases. It is the result of an increased frequency of breathing, an increased tidal volume, or a combination of both. It causes an excess intake of oxygen and the blowing off of carbon dioxide.
The circulation of the BLOOD through the MICROVASCULAR NETWORK.
A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.
Post-systolic relaxation of the HEART, especially the HEART VENTRICLES.
The visualization of tissues during pregnancy through recording of the echoes of ultrasonic waves directed into the body. The procedure may be applied with reference to the mother or the fetus and with reference to organs or the detection of maternal or fetal disease.
Artery formed by the bifurcation of the internal carotid artery (CAROTID ARTERY, INTERNAL). Branches of the anterior cerebral artery supply the CAUDATE NUCLEUS; INTERNAL CAPSULE; PUTAMEN; SEPTAL NUCLEI; GYRUS CINGULI; and surfaces of the FRONTAL LOBE and PARIETAL LOBE.
The presence of an increased amount of blood in a body part or an organ leading to congestion or engorgement of blood vessels. Hyperemia can be due to increase of blood flow into the area (active or arterial), or due to obstruction of outflow of blood from the area (passive or venous).
The number of times the HEART VENTRICLES contract per unit of time, usually per minute.
The visualization of deep structures of the body by recording the reflections or echoes of ultrasonic pulses directed into the tissues. Use of ultrasound for imaging or diagnostic purposes employs frequencies ranging from 1.6 to 10 megahertz.
Theoretical representations that simulate the behavior or activity of the cardiovascular system, processes, or phenomena; includes the use of mathematical equations, computers and other electronic equipment.
The vessels carrying blood away from the heart.
The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.
Pressure within the cranial cavity. It is influenced by brain mass, the circulatory system, CSF dynamics, and skull rigidity.
Period of contraction of the HEART, especially of the HEART VENTRICLES.
The heart rate of the FETUS. The normal range at term is between 120 and 160 beats per minute.
The arterial trunk that arises from the abdominal aorta and after a short course divides into the left gastric, common hepatic and splenic arteries.
The veins and arteries of the HEART.
The processes whereby the internal environment of an organism tends to remain balanced and stable.
The physiological widening of BLOOD VESSELS by relaxing the underlying VASCULAR SMOOTH MUSCLE.
One of the CARBONIC ANHYDRASE INHIBITORS that is sometimes effective against absence seizures. It is sometimes useful also as an adjunct in the treatment of tonic-clonic, myoclonic, and atonic seizures, particularly in women whose seizures occur or are exacerbated at specific times in the menstrual cycle. However, its usefulness is transient often because of rapid development of tolerance. Its antiepileptic effect may be due to its inhibitory effect on brain carbonic anhydrase, which leads to an increased transneuronal chloride gradient, increased chloride current, and increased inhibition. (From Smith and Reynard, Textbook of Pharmacology, 1991, p337)
The age of the conceptus, beginning from the time of FERTILIZATION. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last MENSTRUATION which is about 2 weeks before OVULATION and fertilization.
Drugs used to cause dilation of the blood vessels.
The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)
Changes in the observed frequency of waves (as sound, light, or radio waves) due to the relative motion of source and observer. The effect was named for the 19th century Austrian physicist Johann Christian Doppler.
The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.
Elements of limited time intervals, contributing to particular results or situations.
An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.
A large vessel supplying the whole length of the small intestine except the superior part of the duodenum. It also supplies the cecum and the ascending part of the colon and about half the transverse part of the colon. It arises from the anterior surface of the aorta below the celiac artery at the level of the first lumbar vertebra.
The failure of a FETUS to attain its expected FETAL GROWTH at any GESTATIONAL AGE.
The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.
A polygonal anastomosis at the base of the brain formed by the internal carotid (CAROTID ARTERY, INTERNAL), proximal parts of the anterior, middle, and posterior cerebral arteries (ANTERIOR CEREBRAL ARTERY; MIDDLE CEREBRAL ARTERY; POSTERIOR CEREBRAL ARTERY), the anterior communicating artery and the posterior communicating arteries.
Echocardiography applying the Doppler effect, with the superposition of flow information as colors on a gray scale in a real-time image.
Branch of the common carotid artery which supplies the anterior part of the brain, the eye and its appendages, the forehead and nose.
The circulation of BLOOD, of both the mother and the FETUS, through the PLACENTA.
Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.
Maintenance of blood flow to an organ despite obstruction of a principal vessel. Blood flow is maintained through small vessels.
The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.
The deformation and flow behavior of BLOOD and its elements i.e., PLASMA; ERYTHROCYTES; WHITE BLOOD CELLS; and BLOOD PLATELETS.
A standard and widely accepted diagnostic test used to identify patients who have a vasodepressive and/or cardioinhibitory response as a cause of syncope. (From Braunwald, Heart Disease, 7th ed)
The heart of the fetus of any viviparous animal. It refers to the heart in the postembryonic period and is differentiated from the embryonic heart (HEART/embryology) only on the basis of time.
Artery formed by the bifurcation of the BASILAR ARTERY. Branches of the posterior cerebral artery supply portions of the OCCIPITAL LOBE; PARIETAL LOBE; inferior temporal gyrus, brainstem, and CHOROID PLEXUS.
The neural systems which act on VASCULAR SMOOTH MUSCLE to control blood vessel diameter. The major neural control is through the sympathetic nervous system.
A significant drop in BLOOD PRESSURE after assuming a standing position. Orthostatic hypotension is a finding, and defined as a 20-mm Hg decrease in systolic pressure or a 10-mm Hg decrease in diastolic pressure 3 minutes after the person has risen from supine to standing. Symptoms generally include DIZZINESS, blurred vision, and SYNCOPE.
Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic.
The circulation of blood through the BLOOD VESSELS supplying the abdominal VISCERA.
A clinical manifestation of abnormal increase in the amount of carbon dioxide in arterial blood.
Technique using an instrument system for making, processing, and displaying one or more measurements on individual cells obtained from a cell suspension. Cells are usually stained with one or more fluorescent dyes specific to cell components of interest, e.g., DNA, and fluorescence of each cell is measured as it rapidly transverses the excitation beam (laser or mercury arc lamp). Fluorescence provides a quantitative measure of various biochemical and biophysical properties of the cell, as well as a basis for cell sorting. Other measurable optical parameters include light absorption and light scattering, the latter being applicable to the measurement of cell size, shape, density, granularity, and stain uptake.
The internal resistance of the BLOOD to shear forces. The in vitro measure of whole blood viscosity is of limited clinical utility because it bears little relationship to the actual viscosity within the circulation, but an increase in the viscosity of circulating blood can contribute to morbidity in patients suffering from disorders such as SICKLE CELL ANEMIA and POLYCYTHEMIA.
The circulation of the BLOOD through the LUNGS.
Determination of the shortest time interval between the injection of a substance in the vein and its arrival at some distant site in sufficient concentration to produce a recognizable end result. It represents approximately the inverse of the average velocity of blood flow between two points.
The position or attitude of the body.
Volume of circulating BLOOD. It is the sum of the PLASMA VOLUME and ERYTHROCYTE VOLUME.
The pressure that would be exerted by one component of a mixture of gases if it were present alone in a container. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
An alkaloid found in opium but not closely related to the other opium alkaloids in its structure or pharmacological actions. It is a direct-acting smooth muscle relaxant used in the treatment of impotence and as a vasodilator, especially for cerebral vasodilation. The mechanism of its pharmacological actions is not clear, but it apparently can inhibit phosphodiesterases and it may have direct actions on calcium channels.
The blood vessels which supply and drain the RETINA.
The hollow thick-walled muscular organ in the female PELVIS. It consists of the fundus (the body) which is the site of EMBRYO IMPLANTATION and FETAL DEVELOPMENT. Beyond the isthmus at the perineal end of fundus, is CERVIX UTERI (the neck) opening into VAGINA. Beyond the isthmi at the upper abdominal end of fundus, are the FALLOPIAN TUBES.
Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues using a transducer placed in the esophagus.
The physiological narrowing of BLOOD VESSELS by contraction of the VASCULAR SMOOTH MUSCLE.
Echocardiography applying the Doppler effect, with velocity detection combined with range discrimination. Short bursts of ultrasound are transmitted at regular intervals and the echoes are demodulated as they return.
The volume of BLOOD passing through the HEART per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with STROKE VOLUME (volume per beat).
A nucleoside that is composed of ADENINE and D-RIBOSE. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter.
The circulation of the BLOOD through the vessels of the KIDNEY.
Either of the two principal arteries on both sides of the neck that supply blood to the head and neck; each divides into two branches, the internal carotid artery and the external carotid artery.
The rate at which oxygen is used by a tissue; microliters of oxygen STPD used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (Stedman, 25th ed, p346)
The valve between the left atrium and left ventricle of the heart.
The hemodynamic and electrophysiological action of the left HEART VENTRICLE. Its measurement is an important aspect of the clinical evaluation of patients with heart disease to determine the effects of the disease on cardiac performance.
Symptoms of cerebral hypoperfusion or autonomic overaction which develop while the subject is standing, but are relieved on recumbency. Types of this include NEUROCARDIOGENIC SYNCOPE; POSTURAL ORTHOSTATIC TACHYCARDIA SYNDROME; and neurogenic ORTHOSTATIC HYPOTENSION. (From Noseworthy, JH., Neurological Therapeutics Principles and Practice, 2007, p2575-2576)
An infant during the first month after birth.
Small uniformly-sized spherical particles, of micrometer dimensions, frequently labeled with radioisotopes or various reagents acting as tags or markers.
The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.
A human infant born before 37 weeks of GESTATION.
The volume of packed RED BLOOD CELLS in a blood specimen. The volume is measured by centrifugation in a tube with graduated markings, or with automated blood cell counters. It is an indicator of erythrocyte status in disease. For example, ANEMIA shows a low value; POLYCYTHEMIA, a high value.
A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.
The movement of the BLOOD as it is pumped through the CARDIOVASCULAR SYSTEM.
Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)
A fetal blood vessel connecting the pulmonary artery with the descending aorta.
Unstable isotopes of xenon that decay or disintegrate emitting radiation. Xe atoms with atomic weights 121-123, 125, 127, 133, 135, 137-145 are radioactive xenon isotopes.
Recording of change in the size of a part as modified by the circulation in it.
The vessels carrying blood away from the capillary beds.
Ultrasonography applying the Doppler effect combined with real-time imaging. The real-time image is created by rapid movement of the ultrasound beam. A powerful advantage of this technique is the ability to estimate the velocity of flow from the Doppler shift frequency.
Radiography of the vascular system of the heart muscle after injection of a contrast medium.
The failure by the observer to measure or identify a phenomenon accurately, which results in an error. Sources for this may be due to the observer's missing an abnormality, or to faulty technique resulting in incorrect test measurement, or to misinterpretation of the data. Two varieties are inter-observer variation (the amount observers vary from one another when reporting on the same material) and intra-observer variation (the amount one observer varies between observations when reporting more than once on the same material).
Pathological processes which result in the partial or complete obstruction of ARTERIES. They are characterized by greatly reduced or absence of blood flow through these vessels. They are also known as arterial insufficiency.
The rhythmical expansion and contraction of an ARTERY produced by waves of pressure caused by the ejection of BLOOD from the left ventricle of the HEART as it contracts.
The hemodynamic and electrophysiological action of the LEFT ATRIUM.
The two principal arteries supplying the structures of the head and neck. They ascend in the neck, one on each side, and at the level of the upper border of the thyroid cartilage, each divides into two branches, the external (CAROTID ARTERY, EXTERNAL) and internal (CAROTID ARTERY, INTERNAL) carotid arteries.
In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test.
Freedom from activity.
The artery formed by the union of the right and left vertebral arteries; it runs from the lower to the upper border of the pons, where it bifurcates into the two posterior cerebral arteries.
A spectrum of pathological conditions of impaired blood flow in the brain. They can involve vessels (ARTERIES or VEINS) in the CEREBRUM, the CEREBELLUM, and the BRAIN STEM. Major categories include INTRACRANIAL ARTERIOVENOUS MALFORMATIONS; BRAIN ISCHEMIA; CEREBRAL HEMORRHAGE; and others.
The posture of an individual lying face up.
The circulation of BLOOD through the LIVER.
Non-invasive method of vascular imaging and determination of internal anatomy without injection of contrast media or radiation exposure. The technique is used especially in CEREBRAL ANGIOGRAPHY as well as for studies of other vascular structures.
External decompression applied to the lower body. It is used to study orthostatic intolerance and the effects of gravitation and acceleration, to produce simulated hemorrhage in physiologic research, to assess cardiovascular function, and to reduce abdominal stress during childbirth.
An imbalance between myocardial functional requirements and the capacity of the CORONARY VESSELS to supply sufficient blood flow. It is a form of MYOCARDIAL ISCHEMIA (insufficient blood supply to the heart muscle) caused by a decreased capacity of the coronary vessels.
The innermost layer of the three meninges covering the brain and spinal cord. It is the fine vascular membrane that lies under the ARACHNOID and the DURA MATER.
A phosphodiesterase inhibitor that blocks uptake and metabolism of adenosine by erythrocytes and vascular endothelial cells. Dipyridamole also potentiates the antiaggregating action of prostacyclin. (From AMA Drug Evaluations Annual, 1994, p752)
Central retinal vein and its tributaries. It runs a short course within the optic nerve and then leaves and empties into the superior ophthalmic vein or cavernous sinus.
A branch of the abdominal aorta which supplies the kidneys, adrenal glands and ureters.
Forced expiratory effort against a closed GLOTTIS.
A volatile vasodilator which relieves ANGINA PECTORIS by stimulating GUANYLATE CYCLASE and lowering cytosolic calcium. It is also sometimes used for TOCOLYSIS and explosives.
The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light.
Narrowing or stricture of any part of the CAROTID ARTERIES, most often due to atherosclerotic plaque formation. Ulcerations may form in atherosclerotic plaques and induce THROMBUS formation. Platelet or cholesterol emboli may arise from stenotic carotid lesions and induce a TRANSIENT ISCHEMIC ATTACK; CEREBROVASCULAR ACCIDENT; or temporary blindness (AMAUROSIS FUGAX). (From Adams et al., Principles of Neurology, 6th ed, pp 822-3)
Manometric pressure of the CEREBROSPINAL FLUID as measured by lumbar, cerebroventricular, or cisternal puncture. Within the cranial cavity it is called INTRACRANIAL PRESSURE.
Pathophysiological conditions of the FETUS in the UTERUS. Some fetal diseases may be treated with FETAL THERAPIES.
Plethysmographic determination in which the intensity of light reflected from the skin surface and the red cells below is measured to determine the blood volume of the respective area. There are two types, transmission and reflectance.
The main artery of the thigh, a continuation of the external iliac artery.
The use of ultrasound to guide minimally invasive surgical procedures such as needle ASPIRATION BIOPSY; DRAINAGE; etc. Its widest application is intravascular ultrasound imaging but it is useful also in urology and intra-abdominal conditions.
Abnormally low BLOOD PRESSURE that can result in inadequate blood flow to the brain and other vital organs. Common symptom is DIZZINESS but greater negative impacts on the body occur when there is prolonged depravation of oxygen and nutrients.
Pathological conditions of intracranial ARTERIES supplying the CEREBRUM. These diseases often are due to abnormalities or pathological processes in the ANTERIOR CEREBRAL ARTERY; MIDDLE CEREBRAL ARTERY; and POSTERIOR CEREBRAL ARTERY.
A sympathomimetic agent with specificity for alpha-1 adrenergic receptors. It is used to maintain BLOOD PRESSURE in hypotensive states such as following SPINAL ANESTHESIA.
The hollow, muscular organ that maintains the circulation of the blood.
A purely physical condition which exists within any material because of strain or deformation by external forces or by non-uniform thermal expansion; expressed quantitatively in units of force per unit area.
Relatively complete absence of oxygen in one or more tissues.
Analysis based on the mathematical function first formulated by Jean-Baptiste-Joseph Fourier in 1807. The function, known as the Fourier transform, describes the sinusoidal pattern of any fluctuating pattern in the physical world in terms of its amplitude and its phase. It has broad applications in biomedicine, e.g., analysis of the x-ray crystallography data pivotal in identifying the double helical nature of DNA and in analysis of other molecules, including viruses, and the modified back-projection algorithm universally used in computerized tomography imaging, etc. (From Segen, The Dictionary of Modern Medicine, 1992)
The first branch of the SUBCLAVIAN ARTERY with distribution to muscles of the NECK; VERTEBRAE; SPINAL CORD; CEREBELLUM; and interior of the CEREBRUM.
Procedures in which placement of CARDIAC CATHETERS is performed for therapeutic or diagnostic procedures.
A method of computed tomography that uses radionuclides which emit a single photon of a given energy. The camera is rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer is then used to reconstruct the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the organ. The advantages of SPECT are that it can be used to observe biochemical and physiological processes as well as size and volume of the organ. The disadvantage is that, unlike positron-emission tomography where the positron-electron annihilation results in the emission of 2 photons at 180 degrees from each other, SPECT requires physical collimation to line up the photons, which results in the loss of many available photons and hence degrades the image.
Contractile activity of the MYOCARDIUM.
Benzenesulfonate derivative used as a systemic hemostatic.
The condition of an anatomical structure's being constricted beyond normal dimensions.
The act of breathing with the LUNGS, consisting of INHALATION, or the taking into the lungs of the ambient air, and of EXHALATION, or the expelling of the modified air which contains more CARBON DIOXIDE than the air taken in (Blakiston's Gould Medical Dictionary, 4th ed.). This does not include tissue respiration (= OXYGEN CONSUMPTION) or cell respiration (= CELL RESPIRATION).
The short wide vessel arising from the conus arteriosus of the right ventricle and conveying unaerated blood to the lungs.
The middle third of a human PREGNANCY, from the beginning of the 15th through the 28th completed week (99 to 196 days) of gestation.
Measurement of oxygen and carbon dioxide in the blood.
The amount of BLOOD pumped out of the HEART per beat, not to be confused with cardiac output (volume/time). It is calculated as the difference between the end-diastolic volume and the end-systolic volume.
Anesthesia caused by the breathing of anesthetic gases or vapors or by insufflating anesthetic gases or vapors into the respiratory tract.
A subfield of acoustics dealing in the radio frequency range higher than acoustic SOUND waves (approximately above 20 kilohertz). Ultrasonic radiation is used therapeutically (DIATHERMY and ULTRASONIC THERAPY) to generate HEAT and to selectively destroy tissues. It is also used in diagnostics, for example, ULTRASONOGRAPHY; ECHOENCEPHALOGRAPHY; and ECHOCARDIOGRAPHY, to visually display echoes received from irradiated tissues.
Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable.
Veins draining the cerebrum.
Localized reduction of blood flow to brain tissue due to arterial obstruction or systemic hypoperfusion. This frequently occurs in conjunction with brain hypoxia (HYPOXIA, BRAIN). Prolonged ischemia is associated with BRAIN INFARCTION.
The minute vessels that connect the arterioles and venules.
A noble gas with the atomic symbol Xe, atomic number 54, and atomic weight 131.30. It is found in the earth's atmosphere and has been used as an anesthetic.
Tomography using radioactive emissions from injected RADIONUCLIDES and computer ALGORITHMS to reconstruct an image.
Bleeding into the intracranial or spinal SUBARACHNOID SPACE, most resulting from INTRACRANIAL ANEURYSM rupture. It can occur after traumatic injuries (SUBARACHNOID HEMORRHAGE, TRAUMATIC). Clinical features include HEADACHE; NAUSEA; VOMITING, nuchal rigidity, variable neurological deficits and reduced mental status.
A free radical gas produced endogenously by a variety of mammalian cells, synthesized from ARGININE by NITRIC OXIDE SYNTHASE. Nitric oxide is one of the ENDOTHELIUM-DEPENDENT RELAXING FACTORS released by the vascular endothelium and mediates VASODILATION. It also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to the vascular endothelium. Nitric oxide activates cytosolic GUANYLATE CYCLASE and thus elevates intracellular levels of CYCLIC GMP.
A stable, non-explosive inhalation anesthetic, relatively free from significant side effects.
Increased pressure within the cranial vault. This may result from several conditions, including HYDROCEPHALUS; BRAIN EDEMA; intracranial masses; severe systemic HYPERTENSION; PSEUDOTUMOR CEREBRI; and other disorders.
Posture while lying with the head lower than the rest of the body. Extended time in this position is associated with temporary physiologic disturbances.
Persons with no known significant health problems who are recruited to participate in research to test a new drug, device, or intervention as controls for a patient group. (from http://clinicalcenter.nih.gov/recruit/volunteers.html, accessed 2/14/2013)
A vertical distance measured from a known level on the surface of a planet or other celestial body.
The inferior part of the lower extremity between the KNEE and the ANKLE.
Constriction of arteries in the SKULL due to sudden, sharp, and often persistent smooth muscle contraction in blood vessels. Intracranial vasospasm results in reduced vessel lumen caliber, restricted blood flow to the brain, and BRAIN ISCHEMIA that may lead to hypoxic-ischemic brain injury (HYPOXIA-ISCHEMIA, BRAIN).
A powerful vasodilator used in emergencies to lower blood pressure or to improve cardiac function. It is also an indicator for free sulfhydryl groups in proteins.
A phenethylamine found in EPHEDRA SINICA. PSEUDOEPHEDRINE is an isomer. It is an alpha- and beta-adrenergic agonist that may also enhance release of norepinephrine. It has been used for asthma, heart failure, rhinitis, and urinary incontinence, and for its central nervous system stimulatory effects in the treatment of narcolepsy and depression. It has become less extensively used with the advent of more selective agonists.
The constant checking on the state or condition of a patient during the course of a surgical operation (e.g., checking of vital signs).
Substances used to allow enhanced visualization of tissues.
The continuation of the axillary artery; it branches into the radial and ulnar arteries.
The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs.
Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.
The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.
A noninvasive technique that uses the differential absorption properties of hemoglobin and myoglobin to evaluate tissue oxygenation and indirectly can measure regional hemodynamics and blood flow. Near-infrared light (NIR) can propagate through tissues and at particular wavelengths is differentially absorbed by oxygenated vs. deoxygenated forms of hemoglobin and myoglobin. Illumination of intact tissue with NIR allows qualitative assessment of changes in the tissue concentration of these molecules. The analysis is also used to determine body composition.
The pressure of the fluids in the eye.
The excision of the thickened, atheromatous tunica intima of a carotid artery.
Loss of consciousness due to a reduction in blood pressure that is associated with an increase in vagal tone and peripheral vasodilation.
The period following a surgical operation.
The determination of oxygen-hemoglobin saturation of blood either by withdrawing a sample and passing it through a classical photoelectric oximeter or by electrodes attached to some translucent part of the body like finger, earlobe, or skin fold. It includes non-invasive oxygen monitoring by pulse oximetry.
The motion of fluids, especially noncompressible liquids, under the influence of internal and external forces.
Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.
Single pavement layer of cells which line the luminal surface of the entire vascular system and regulate the transport of macromolecules and blood components.
Nitrogen oxide (N2O). A colorless, odorless gas that is used as an anesthetic and analgesic. High concentrations cause a narcotic effect and may replace oxygen, causing death by asphyxia. It is also used as a food aerosol in the preparation of whipping cream.
The valve consisting of three cusps situated between the right atrium and right ventricle of the heart.
Narrowing or constriction of a coronary artery.
The condition of an anatomical structure's being dilated beyond normal dimensions.
Studies to determine the advantages or disadvantages, practicability, or capability of accomplishing a projected plan, study, or project.
The continuous measurement of physiological processes, blood pressure, heart rate, renal output, reflexes, respiration, etc., in a patient or experimental animal; includes pharmacologic monitoring, the measurement of administered drugs or their metabolites in the blood, tissues, or urine.
The main trunk of the systemic arteries.
Persistently high systemic arterial BLOOD PRESSURE. Based on multiple readings (BLOOD PRESSURE DETERMINATION), hypertension is currently defined as when SYSTOLIC PRESSURE is consistently greater than 140 mm Hg or when DIASTOLIC PRESSURE is consistently 90 mm Hg or more.
Statistical models in which the value of a parameter for a given value of a factor is assumed to be equal to a + bx, where a and b are constants. The models predict a linear regression.
Interruption of sympathetic pathways, by local injection of an anesthetic agent, at any of four levels: peripheral nerve block, sympathetic ganglion block, extradural block, and subarachnoid block.
A class of compounds that reduces the secretion of H+ ions by the proximal kidney tubule through inhibition of CARBONIC ANHYDRASES.
The thoracolumbar division of the autonomic nervous system. Sympathetic preganglionic fibers originate in neurons of the intermediolateral column of the spinal cord and project to the paravertebral and prevertebral ganglia, which in turn project to target organs. The sympathetic nervous system mediates the body's response to stressful situations, i.e., the fight or flight reactions. It often acts reciprocally to the parasympathetic system.
Dilation of an occluded coronary artery (or arteries) by means of a balloon catheter to restore myocardial blood supply.
A subtype of striated muscle, attached by TENDONS to the SKELETON. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles.
Studies comparing two or more treatments or interventions in which the subjects or patients, upon completion of the course of one treatment, are switched to another. In the case of two treatments, A and B, half the subjects are randomly allocated to receive these in the order A, B and half to receive them in the order B, A. A criticism of this design is that effects of the first treatment may carry over into the period when the second is given. (Last, A Dictionary of Epidemiology, 2d ed)
Injections made into a vein for therapeutic or experimental purposes.
The veins that return the oxygenated blood from the lungs to the left atrium of the heart.
Radiography of the vascular system of the brain after injection of a contrast medium.
Physical activity which is usually regular and done with the intention of improving or maintaining PHYSICAL FITNESS or HEALTH. Contrast with PHYSICAL EXERTION which is concerned largely with the physiologic and metabolic response to energy expenditure.

The effect of cardiac contraction on collateral resistance in the canine heart. (1/7943)

We determined whether the coronary collateral vessels develop an increased resistance to blood flow during systole as does the cognate vascular bed. Collateral resistance was estimated by measuring retrograde flow rate from a distal branch of the left anterior descending coronary artery while the main left coronary artery was perfused at a constant pressure. Retrograde flow rate was measured before and during vagal arrest. We found that in 10 dogs the prolonged diastole experienced when the heart was stopped caused no significant change in the retrograde flow rate, which indicated that systole has little effect on the collateral resistance. However, when left ventricular end-diastolic pressure was altered by changing afterload or contractility, a direct relationship between end-diastolic pressure and collateral resistance was noted.  (+info)

Investigation of the theory and mechanism of the origin of the second heart sound. (2/7943)

To investigate further the origin of the second heart sound we studied human subjects, dogs, and a model in vitro of the cardiovascular system. Intra-arterial sound, pressure, and, where possible, flow and high speed cine (2,000 frames/sec) were utilized. The closure sound of the semilunar valves was of higher amplitude in be ventricles than in their respective arterial cavities. The direction of inscription of the main components of intra-arterial sound were opposite in direction to the components of intraventricular sound. Notches, representative of pressure increments, were noted on the ventricular pressure tracings and were coincident with the components of sound. The amplitude of the closure sound varied with diastolic pressure, but remained unchanged with augmentation of forward and retrograde aortic flow. Cines showed second sound to begin after complete valvular closure, and average leaflet closure rate was constant regardless of pressure. Hence, the semilunar valves, when closed, act as an elastic membrane and, when set into motion, generate compression and expansion of the blood, producing transient pressure changes indicative of sound. The magnitude of the initial stretch is related to the differential pressure between the arterial and ventricular chambers. Sound transients which follow the major components of the second sound appear to be caused by the continuing stretch and recoil of the leaflets. Clinically unexplained findings such as the reduced or absent second sound in calcific aortic stenosis and its paradoxical presence in congenital aortic stenosis may be explained by those observations.  (+info)

Flow-mediated vasodilation and distensibility of the brachial artery in renal allograft recipients. (3/7943)

BACKGROUND: Alterations of large artery function and structure are frequently observed in renal allograft recipients. However, endothelial function has not yet been assessed in this population. METHODS: Flow-mediated vasodilation is a useful index of endothelial function. We measured the diameter and distensibility of the brachial artery at rest using high-resolution ultrasound and Doppler frequency analysis of vessel wall movements in the M mode. Thereafter, changes in brachial artery diameter were measured during reactive hyperemia (after 4 min of forearm occlusion) in 16 cyclosporine-treated renal allograft recipients and 16 normal controls of similar age and sex ratio. Nitroglycerin-mediated vasodilation was measured to assess endothelium-independent vasodilation. Brachial artery blood pressure was measured using an automatic sphygmomanometer, and brachial artery flow was estimated using pulsed Doppler. RESULTS: Distensibility was reduced in renal allograft recipients (5.31 +/- 0. 74 vs. 9.10 +/- 0.94 x 10-3/kPa, P = 0.003, mean +/- sem), while the brachial artery diameter at rest was higher (4.13 +/- 0.14 vs. 3.25 +/- 0.14 mm, P < 0.001). Flow-mediated vasodilation was significantly reduced in renal allograft recipients (0.13 +/- 0.08 vs. 0.60 +/- 0.08 mm or 3 +/- 2 vs. 19 +/- 3%, both P < 0.001). However, nitroglycerin-mediated vasodilation was similar in renal allograft recipients and controls (0.76 +/- 0.10 vs. 0.77 +/- 0.09 mm, NS, or 19 +/- 3 vs. 22 +/- 2%, NS). There were no significant differences in brachial artery flow at rest and during reactive hyperemia between both groups. The impairments of flow-mediated vasodilation and distensibility in renal allograft recipients remained significant after correction for serum cholesterol, creatinine, parathyroid hormone concentrations, end-diastolic diameter, as well as blood pressure levels, and were also present in eight renal allograft recipients not treated with cyclosporine. Flow-mediated vasodilation was not related to distensibility in either group. CONCLUSIONS: The results show impaired endothelial function and reduced brachial artery distensibility in renal allograft recipients. The impairments of flow-mediated vasodilation and distensibility are not attributable to a diminished brachial artery vasodilator capacity, because endothelium-independent vasodilation was preserved in renal allograft recipients.  (+info)

Profile of neurohumoral agents on mesenteric and intestinal blood flow in health and disease. (4/7943)

The mesenteric and intestinal blood flow is organized and regulated to support normal intestinal function, and the regulation of blood flow is, in part, determined by intestinal function itself. In the process of the development and adaptation of the intestinal mucosa for the support of the digestive processes and host defense mechanisms, and the muscle layers for propulsion of foodstuffs, a specialized microvascular architecture has evolved in each tissue layer. Compromised mesenteric and intestinal blood flow, which can be common in the elderly, may lead to devastating clinical consequences. This problem, which can be caused by vasospasm at the microvascular level, can cause intestinal ischaemia to any of the layers of the intestinal wall, and can initiate pathological events which promote significant clinical consequences such as diarrhea, abdominal angina and intestinal infarction. The objective of this review is to provide the reader with some general concepts of the mechanisms by which neurohumoral vasoactive substances influence mesenteric and intestinal arterial blood flow in health and disease with focus on transmural transport processes (absorption and secretion). The complex regulatory mechanisms of extrinsic (sympathetic-parasympathetic and endocrine) and intrinsic (enteric nervous system and humoral endocrine) components are presented. More extensive reviews of platelet function, atherosclerosis, hypertension, diabetes mellitus, the carcinoid syndrome, 5-hydroxytryptamine and nitric oxide regulation of vascular tone are presented in this context. The possible options of pharmacological intervention (e.g. vasodilator agonists and vasoconstrictor antagonists) used for the treatment of abnormal mesenteric and intestinal vascular states are also discussed.  (+info)

Venous ulceration and continuous flow in the long saphenous vein. (5/7943)

OBJECTIVE: To determine the clinical significance of continuous flow in the long saphenous vein in limbs with venous ulceration. DESIGN: Retrospective review. PATIENTS AND METHODS: Review of 1608 consecutive limbs undergoing colour duplex scanning for venous disease over a 43 month period. RESULTS: Continuous flow in the long saphenous vein is seen in 8% of limbs with venous ulceration and in 37% of limbs with deep venous obstruction. Sixty-six per cent of ulcerated limbs with continuous flow in the long saphenous vein had deep venous obstruction, 27% had deep venous reflux with cellulitis and 7% had lymphoedema in addition to venous ulceration. CONCLUSION: Continuous flow in the long saphenous vein in patients with venous ulceration should alert the clinician to the possibility of deep venous obstruction. Such limbs should be treated by compression bandaging with extreme caution.  (+info)

Brightness alters Heidelberg retinal flowmeter measurements in an in vitro model. (6/7943)

PURPOSE: The Heidelberg Retinal Flowmeter (HRF), a laser Doppler flowmetry device, has captured interest as a research and clinical tool for measurement of ocular blood flow. Concerns remain about the range and accuracy of the values that it reports. METHODS: An in vitro blood-flow model was constructed to provide well-controlled laminar flow through a glass capillary for assessment by HRF. A change in material behind the glass capillary was used to simulate changing brightness conditions between eyes. RESULTS: Velocities reported by the HRF correlated linearly to true velocities below 8.8 mm/sec. Beyond 8.8 mm/sec, HRF readings fluctuated randomly. True velocity and HRF reported velocities were highly correlated, with r = 0.967 (P < 0.001) from 0.0 mm/sec to 2.7 mm/sec mean velocity using a light background, and r = 0.900 (P < 0.001) from 2.7 mm/sec to 8.8 mm/sec using a darker background. However, a large change in the y-intercept occurred in the calibration curve with the background change. CONCLUSIONS: The HRF may report velocities inaccurately because of varying brightness in the fundus. In the present experiment, a darker background produced an overreporting of velocities. An offset, possibly introduced by a noise correction routine, apparently contributed to the inaccuracies of the HRF measurements. Such offsets vary with local and global brightness. Therefore, HRF measurements may be error prone when comparing eyes. When used to track perfusion in a single eye over time, meaningful comparison may be possible if meticulous care is taken to align vessels and intensity controls to achieve a similar level of noise correction between measurements.  (+info)

Analysis of blood flow in the long posterior ciliary artery of the cat. (7/7943)

PURPOSE: Experiments were undertaken to use a new technique for direct on-line measurement of blood flow in the long posterior ciliary artery (LPCA) in cats and to evaluate possible physiological mechanisms controlling blood flow in the vascular beds perfused by this artery. METHODS: Blood flow in the temporal LPCA was measured on a continuous basis using ultrasonic flowmetry in anesthetized cats. Effects of acute sectioning of the sympathetic nerve and changes in LPCA and cerebral blood flows in response to altered levels of inspired CO2 and O2 were tested in some animals. In others, the presence of vascular autoregulatory mechanisms in response to stepwise elevations of intraocular pressure was studied. RESULTS: Blood flow in the temporal LPCA averaged 0.58+/-0.03 ml/min in 45 cats anesthetized with pentobarbital. Basal LPCA blood flow was not altered by acute sectioning of the sympathetic nerve or by changes in low levels of inspired CO2 and O2, although 10% CO2 caused a modest increase. Stepwise elevations of intraocular pressure resulted in comparable stepwise decreases of LPCA blood flow, with perfusion pressure declining in a linear manner throughout the perfusion-pressure range. CONCLUSIONS: Ultrasonic flowmetry seems to be a useful tool for continuous on-line measurement of LPCA blood flow in the cat eye. Blood flow to vascular beds perfused by this artery does not seem to be under sympathetic neural control and is refractory to modest alterations of blood gas levels of CO2 and O2. Blood vessels perfused by the LPCA show no clear autoregulatory mechanisms.  (+info)

Demonstration of rapid onset vascular endothelial dysfunction after hyperhomocysteinemia: an effect reversible with vitamin C therapy. (8/7943)

BACKGROUND: Hyperhomocysteinemia is a major and independent risk factor for vascular disease. The mechanisms by which homocysteine promotes atherosclerosis are not well understood. We hypothesized that elevated homocysteine concentrations are associated with rapid onset endothelial dysfunction, which is mediated through oxidant stress mechanisms and can be inhibited by the antioxidant vitamin C. METHODS AND RESULTS: We studied 17 healthy volunteers (10 male and 7 female) aged 33 (range 21 to 59) years. Brachial artery diameter responses to hyperemic flow (endothelium dependent), and glyceryltrinitrate (GTN, endothelium independent) were measured with high resolution ultrasound at 0 hours (fasting), 2 hours, and 4 hours after (1) oral methionine (L-methionine 100 mg/kg), (2) oral methionine preceded by vitamin C (1g/day, for 1 week), and (3) placebo, on separate days and in random order. Plasma homocysteine increased (0 hours, 12.8+/-1.4; 2 hours, 25.4+/-2.5; and 4 hours, 31. 2+/-3.1 micromol/l, P<0.001), and flow-mediated dilatation fell (0 hours, 4.3+/-0.7; 2 hours, 1.1+/-0.9; and 4 hours, -0.7+/-0.8%) after oral L-methionine. There was an inverse linear relationship between homocysteine concentration and flow-mediated dilatation (P<0. 001). Pretreatment with vitamin C did not affect the rise in homocysteine concentrations after methionine (0 hours, 13.6+/-1.6; 2 hours, 28.3+/-2.9; and 4 hours, 33.8+/-3.7 micromol/l, P=0.27), but did ameliorate the reduction in flow-mediated dilatation (0 hours, 4. 0+/-1.0; 2 hours, 3.5+/-1.2 and 4 hours, 2.8+/-0.7%, P=0.02). GTN-induced endothelium independent brachial artery dilatation was not affected after methionine or methionine preceded by vitamin C. CONCLUSIONS: We conclude that an elevation in homocysteine concentration is associated with an acute impairment of vascular endothelial function that can be prevented by pretreatment with vitamin C in healthy subjects. Our results support the hypothesis that the adverse effects of homocysteine on vascular endothelial cells are mediated through oxidative stress mechanisms.  (+info)

Previous studies have shown that myocardial ischemia results in changes in the pattern of flow through the mitral valve (1-6). These changes in transmitral flow velocity pattern are most likely determined by disease-induced changes in the underlying diastolic properties of the heart (3,6-8). Knowing which diastolic properties determine the transmitral flow velocity pattern and how interactions between diastolic properties modify the overall transmitral flow velocity pattern would be helpful in understanding the hemodynamics of patients with myocardial ischemia.. Several transmitral flow velocity patterns have been reported during myocardial ischemia (5,6,8-10). In one pattern, early flow velocity is decreased, deceleration time is increased, and late flow velocity is increased (5,6,8). The diastolic determinant changed in this pattern is left ventricular relaxation, which is slowed. Slowed left ventricular relaxation is observed in some patients with dilated cardiomyopathy (11,12)and coronary ...
It has previously been demonstrated that predictable changes occur in mitral flow velocities under different loading conditions. The purpose of this study was to relate changes in pulmonary venous and mitral flow velocities during different loading conditions as assessed by transesophageal echocardiography in the operating room. Nineteen patients had measurements of hemodynamics, that is, mitral and pulmonary vein flow velocities during the control situation, a decrease in preload by administration of nitroglycerin, an increase in preload by administration of fluids, and an increase in afterload by infusion of phenylephrine. There was a direct correlation between the changes in the mitral E velocity and the early peak diastolic velocity in the pulmonary vein curves (r = 0.61) as well as a direct correlation between the deceleration time of the mitral and pulmonary venous flow velocities in early diastole (r = 0.84). This indicates that diastolic flow velocity in the pulmonary vein is determined ...
This thesis aims to evaluate the blood flow velocity in the Brachial artery during reactive hyperemia. Primarily to appraise the information it might contain regarding cardiovascular function and cardiovascular risk.. Ultrasonographic doppler measurements of the Brachial artery were made on the 1016 men and women aged 70 included in the prospective investigation of the vasculature in Uppsala seniors (PIVUS) study. Analysis of the blood flow velocity in the forearm was made in comparison to established methods of estimating endothelial function, clinical markers of cardiovascular risk, the Framingham risk score and global atherosclerosis determined by whole body magnetic resonance angiography.. Systolic blood flow velocity was positively related to cardiovascular risk whereas the diastolic velocity was inversely correlated. However, the systolic to diastolic blood flow velocity (SDFV) ratio was more closely associated with cardiovascular risk than its components apart.. Ultrasonographic markers ...
We quantitated phasic epimyocardial microcirculatory coronary blood flow velocity patterns in the beating left ventricle. Using a newly developed floating objective and high-speed cinematography, red cell velocities in small arterioles, capillaries, and small venules and microvascular diameters in the superficial layer of the epimyocardium of beating left ventricle were determined throughout the entire cardiac cycle in open-chest anesthetized dogs. Heart rate was maintained at 140 beats/min by means of left atrial pacing. Peak red cell velocity was observed in midsystole in small arterioles and capillaries, and in late systole in small venules. Abrupt decline in red cell velocity and, in many cases, a momentary cessation or reverse of flow, was observed in these microvessels during the pre-ejection period. The internal diameter of small venule was increased in late systole, while that of small arteriole remained almost constant during the cardiac cycle. Furthermore, in these epimyocardial ...
Doppler ultrasound was used to measure blood flow velocity in the anterior cerebral artery of six premature infants with posthaemorrhagic hydrocephalus, before and after intermittent cerebrospinal fluid (CSF) drainage, on 23 occasions. There was a significant increase in mean blood flow velocity after the drainage procedures (+5.6 cm/s, 95% confidence interval +2.9 to +8.3 cm/s), which was accompanied by a decrease in velocity waveform pulsatility. CSF pressure also fell significantly. In patients with posthaemorrhagic hydrocephalus, intermittent CSF drainage was associated with acute changes in cerebral haemodynamics.. ...
Background and purposeCerebral hyperperfusion has been related to the risk of intracranial hemorrhage (ICH) in stroke patients after vessel recanalization therapy. We hypothesized that after successful mechanical thrombectomy for acute a ...
The ability of pulsed Doppler echocardiography to identify patients with left ventricular systolic dysfunction was evaluated in 12 patients with dilated (congestive) cardiomyopathy. A range-gated, spectrum analyzer-based Doppler velocimeter was used to record blood flow velocity in the ascending aorta and main pulmonary artery. The following blood flow velocity parameters were measured or derived: peak flow velocity, acceleration time, average acceleration, deceleration time, average deceleration, ejection time, and aortic flow velocity integral. Doppler blood flow velocity data in the cardiomyopathy patients were compared to data from 20 normal subjects. Measurements from the ascending aorta revealed that peak aortic flow velocity discriminated between cardiomyopathy patients (mean 47 cm/sec, range 35 to 62) and normal subjects (mean 92 cm/sec, range 72 to 120) with no overlap in data (p , 0.001). Aortic flow velocity integral was also able to separate the patients with dilated cardiomyopathy ...
Maintaining a constant cerebral blood flow during a change in cerebral perfusion pressure is known as autoregulation. The integrity of this phenomenon is considered to be important in preventing cerebral lesions in preterm infants. A study was carried out using Doppler ultrasound measurements of cerebral blood flow velocities (CBFV) as an indicator of alterations in cerebral haemodynamics. CBFV were recorded on a beat to beat basis over 60 second epochs, during which time the cerebral perfusion pressure was changed by rapidly altering the infants posture from horizontal to either 20 degrees head up or head down. An informative response in CBFV was considered to be either (a) a uniphasic, immediate, passive alteration in velocity occurring with the change in posture and without a subsequent change or (b) a biphasic response of an initial change in CBFV followed within 20 seconds by a second response. This latter response is considered to be consistent with autoregulatory activity. A total of 501 ...
1. Peak blood flow acceleration measured in the common carotid artery was compared with peak flow acceleration measured in the ascending aorta of three baboons.. 2. The response to occlusion for 60 s of the circumflex branch or the anterior descending branch of the left coronary artery was investigated.. 3. Both accelerations decreased approximately to the same extent. Peak aortic flow velocity, stroke volume and cardiac output also decreased but to a smaller extent.. 4. It is concluded that peak aortic flow acceleration is a sensitive index of myocardial function during acute coronary occlusion in conscious primates and that peak carotid flow acceleration is an indirect measure of myocardial performance under the same conditions.. ...
Purpose: : Fundus imaging is essential for diagnosing and monitoring common ophthalmic and systemic diseases. The Retinal Function Imager (RFI) is a non-invasive, easy to use, direct qualitative and quantitative imaging method that extends the utility of fundus imaging by providing quantitative information about retinal blood flow velocity. It can also be used for blood oximetry, capillary bed topography, and examining the metabolic state of the retina. Here we concentrated on characterizing blood flow velocity in retinal arteries and veins and accomplishing a nearly two-fold reduction of the variance of blood-flow velocity measurements by coupling the measurement to the heartbeat-cycle. Methods: : One eye of each of 14 healthy volunteers (mean age 30.7 years) was tested. Each subject had at least two separate sessions of imaging using the RFI. Results: : The mean velocity in non-heartbeat synchronized subjects was 6.1± 2.4 mm/sec for secondary and tertiary macular artery segments, and 4.4 ± ...
1] Parallel MRI with extended and averaged GRAPPA kernels (PEAK-GRAPPA): optimized spatiotemporal dynamic imaging. Jung B et al, J Magn Reson Imaging. 2008 Nov;28(5):1226-32. doi: 10.1002/jmri.21561. [2] J.N. Cohn, A.A. Quyyumi, N.K. Hollenberg, and K.A. Jamerson. Surrogate markers for cardiovascular disease. Circulation, 2004,109:31-46. [2] J. M. Tyszka, D. H. Laidlaw, J. W. Asa, and J. M. Silverman. Three-dimensional, time-resolved (4d) relative pressure mapping using magnetic resonance imaging. J Magn Reson Imaging, 12(2):321-329,2000 [3] 4D flow magnetic resonance imaging in bicuspid aortic valve disease demonstrates altered distribution of aortic blood flow helicity Lorenz R et al, Magn Reson Med. 2013 May 28. doi: 10.1002/mrm.24802. [4] H.G. Bogren et al. 4D magnetic resonance velocity mapping of blood flow patterns in the aorta in young vs. elderly normal subjects. J Magn Reson Imaging, 1999; 10(5):861-869.. [5] M.H. Buonocore et al. Analysis of flow patterns using MRI. International ...
Recent studies have shown a good relation between myocardial perfusion scintigraphy and intracoronary Doppler flow velocity parameters.8-11 15 However, the results are not uniform regarding both the best cut off values for the distal coronary flow reserve as well as the agreement between the invasive intracoronary diagnostic technique and non-invasive myocardial perfusion scintigraphy. Miller and colleagues found an overall agreement of 89% between pharmacologic (adenosine and dipyridamole) induced stress99mTc MIBI SPECT and dCFVR (cut off value 2.0) in a cohort of patients with single and multivessel disease.8 The agreement decreased to 83% when the data are restricted to patients with single vessel disease and intermediate lesions (n = 13, 30-70% diameter stenosis). Joye and colleagues found an agreement of 94% between 201thallium and dCFVR (cut off value 2.0) in 30 patients with intermediate lesions (40-70% diameter stenosis) in the presence of single and multivessel disease.9 ...
The hemodynamics of 56 femorodistal saphenous vein bypasses (in situ [n = 53] or reversed [n = 3]) identified to have residual or recurrent graft stenoses were characterized with Doppler-derived blood flow velocity and resting limb systolic pressure measurements. The magnitude and configuration of the graft blood flow velocity waveform were the best predictors of graft stenosis. Transformation of the graft blood flow velocity waveform from a triphasic to a monophasic or biphasic configuration coupled with a low (less than 45 cm/sec) or decrease (greater than 30 cm/sec) in peak systolic blood flow velocity relative to initial postoperative levels reliably predicted the presence of a remote occlusive lesion. In 20 (36%) of the 56 limbs, the ankle-brachial systolic pressure index (ABI) did not identify graft stenosis. The low sensitivity of ABI in the identification of graft stenosis was due to insignificant decrease (less than 0.15) of ABI (n = 11), incompressibility of the tibial arteries (n = 6), or
This paper describes the design and implementation of a two-phase flow meter which can be used in solids-in-water two phase pipe flows to measure the in-situ volume fraction distributions of both phases, the velocity profiles of both phases and the volumetric flow rates for both phases. The system contains an Impedance Cross Correlation (ICC) device which is used in conjunction with an Electromagnetic Velocity Profiler (EVP). Experimental results were obtained for the water and solids velocity and volume fraction profiles in upward inclined flow at 30 degrees to the vertical, in which non-uniform velocity and volume fraction profiles occur.. ...
Background- Lack of high-fidelity simultaneous measurements of pressure and flow velocity distal to a coronary artery stenosis has hampered the study of stenosis pressure drop-velocity (ΔP-v) relationships in patients.. Methods and Results- A novel 0.014-inch dual-sensor (pressure and Doppler velocity) guidewire was used in 15 coronary lesions to obtain per-beat averages of pressure drop and velocity after an intracoronary bolus of adenosine. ΔP-v relations from resting to maximal hyperemic velocity were constructed before and after stepwise executed percutaneous coronary intervention (PCI). Before PCI, half of the ΔP-v relations revealed the presence of a compliant stenosis, which was stabilized by angioplasty. Fractional flow reserve (FFR), coronary flow reserve (CFVR), and velocity-based indices of stenosis resistance (h-SRv) and microvascular resistance (h-MRv) at maximal hyperemia were compared. Stepwise PCI significantly lowered h-SRv, with an initial marked reduction in hyperemic ...
Techniques for the noninvasive evaluation of carotid artery disease are evolving so rapidly that a study such as this meta-analysis by Blakeley and colleagues is in danger of becoming outdated almost as soon as it is published. Nevertheless, this high-quality review synthesizes the current evidence in this field and yields useful information about the test properties of these diagnostic imaging procedures. At present, 2 noninvasive tests are clearly of value to clinicians. Duplex color ultrasonography combines anatomic B-mode views of the carotid bifurcation with Doppler blood flow velocity measurements and is the first test done in most patients suspected of having carotid disease. If substantial (, 70%) stenosis is not found, no further tests are usually necessary. If the results are positive, magnetic resonance angiography is useful for identifying additional vascular lesions and assessing the run-off circulation to the brain. The sensitivity and specificity of these 2 tests are so high that ...
Sixty post-stroke patients were randomly assigned to receive 15 sessions of the usual rehabilitation programme with or without tACS. The NIH Stroke Scale (NIHSS) and the mean blood flow velocity (MFV) and Gosling pulsatility index (PI) captured for the middle, anterior, and posterior cerebral artery were the outcome measures.. Fifteen 30-minute sessions of tACS appear to be effective for enhancing post-stroke patients neurological function. The haemodynamic measures taken indicated that the regaining of function among the patients was largely attributed to a lowering of the vascular autoregulatory activity together with an increase in blood flow velocity at the middle cerebral artery. Future studies should explore the underlying mechanisms mediating the positive effects brought about by tACS in post-stroke rehabilitation. ...
Computer Analysis of Coronary Doppler Flow Velocity: 10.4018/978-1-59904-889-5.ch038: The coronary flow reserve (CFR) represents an important functional parameter to assess epicardial coronary stenosis and to evaluate the integrity of coronary
To the Editor: Steinke and coworkers1 recently reported on the possible advantages of power Doppler imaging (PDI) for quantification of stenoses of the internal carotid artery (ICA): similar to angiography, it should be possible to assess the degree of stenosis of the ICA as the percentage of the diameter reduction from the longitudinal image.. We have tested this examination procedure by comparison with the usual, validated sonography criteria on 40 cases of ICA stenosis. Included in the observation period of the study were all consecutive stenosis findings for which color-coded duplex sonography (CCDS) fulfilled the following criteria: (1) detection of a local flow acceleration in the ICA, (2) peak flow velocity of ≥1 m/s (measurement of the jet flow at the stenosis maximum or, in cases of sound extinction there, directly distal from it), and (3) detection of flow disturbances. Quantification was achieved using the known Doppler criteria.2 In 22% of the cases an adequate evaluation by PDI ...
The flow of air passing through an orifice meter with a beat ratio (beta) of 0.75 and a Reynolds number of 54.700 has been examined using a 3-D laser Doppler velocimeter. The quantities derived from the 4096 simultaneous measurements of three velocity components at each of 670 locations in the flow field include the mean velocity vector, rms fluctuating components, the Reynolds stress tensor, and the entire triple correlation third order tensor. The mean velocity vector field shows the characteristics of flow associated with an orifice meter: fully developed axisymmetric flow undergoe, a large inward radial velocity gradient upstream of the plate. separates from the lip of the plate to form the vena contracts then spreads to the reattachment point at 2.5 pipe radii (10 step heights) downstream. The contour plots of the Reynolds stresses show the anisotropic nature of the flow field in the orifice plate region, and the triple velocity correlations indicate how rapidly the normal and shear stresses return
immediate identification and evaluation of blood flows intraoperatively.. The essential and cost effective intraoperative microvascular instrument that provides you with the sound information you need.. The VTI 20 MHz Microvascular Doppler System was specifically designed for use by surgeons who have a need to interrogate the microvascular vessels. This audio blood flow detector allows for real-time, intraoperative assessment of vessels in a wide variety of surgical specialties.. The System is ideal for intraoperative use in neurosurgical procedures. Combining a miniature probe tip with a high operating frequency, the system emits a tightly focused signal with a shallow depth of signal penetration, imparting a level of precision essential for the neurosurgeon. The sterile- out-of-the-package, single-use probes - optimize patient safety and eliminate probe failure due to reprocessing. ...
Summit Doppler LifeDop 250 Obstetrics / Vascular Doppler Combinations; hand held doppler system; includes popular probe combinations
A dependence on the position of the vessel relative to the location of the placenta was seen. Significant differences were noted when all subgroups were compared (Fig. 17). 1Sl). 27 L-.. 001 n = 71 n = 69 fZB- ~ Internal placental border External placental border ® 0 n = 27 Distant from placenta o Fig. 17. 2 Reproducibility The means and the relative coefficient of variation for the 67% and 90% confidence limits for fetal and uteroplacental blood flow parameters are presented in Table 9. Parameters with a low coefficient of variation show little dispersion about the mean and are most readily reproducible. The median value decreased from 290 ml/kg per minute in pregnancy week 24/0 to 220 mljkg in pregnancy week 40/0 (Fig. 39). - Ratio of mean blood flow volume of fetal common carotid artery to estimated fetal weight showed a decreasing trend until pregnancy week 38/0, followed by a slight increase. The median value changed from 60 ml/kg per minute in pregnancy week 28/0 to 46 ml/kg in ...
Figure 1 presents an en face plane from an age related macular degeneration (AMD) patient. It shows the removal of bias for flow estimation (grayscale is normalized to the highest flow). a) was processed with the method of direct calculation and b) with the MAP estimator. The backstitched scan pattern can be seen in the bias due to gradual changes in the background noise caused by revisitation error (i.e. the error in rescanning the same location). This induced an offset in method a) but the MAP estimator could isolate the flow from it. Figure 2 shows quantitative flow in the same en face plane processed with the MAP estimator to provide flow velocities. The determined flow velocities are within the expected range for retinal capillaries of 0.2 to 3.3 mm/s.. ...
Blood flow measurement using an improved surface integration of velocity vectors (SIVV) technique was tested in in vitro phantoms. SIVV was compared with true flow (12-116 mL/s) in a steady-state model using two angles of insonation (45 degrees and 60 degrees ) and two vessel sizes (internal diameter = 11 and 19 mm). Repeatability of the method was tested at various flow rates for each angle of insonation and vessel. In a univentricular pulsatile model, SIVV flow measured at the mitral inlet was compared to true flow (29-61 mL/s). Correlation was excellent for the 19-mm vessel (r(2)= 0.99). There was a systematic bias but close limits of agreement (mean +/- 2 SD = -24.1% +/- 7.6% at 45 degrees; +16.4% +/- 11.0% at 60 degrees ). Using the 11-mm vessel, a quadratic relationship was demonstrated between between SIVV and true flow (r(2) = 0.98-0.99), regardless of the angle of insonation. In the pulsatile system, good agreement and correlation were shown (r(2) = 0.94, mean +/- 2 SD = -4.7 +/- ...
Neurosurgery. 2010 Sep;67(3 Suppl Operative):ons102-7; discussion ons107. doi: 10.1227/01.NEU.0000383152.50183.81. Clinical Trial
Dynamic cerebral autoregulation (DCA) capacity along with the degree of internal carotid artery (ICA) stenosis and characteristics of the plaque can also play an important role in selection of appropriate treatment strategy. This study aims to classify the patients with severe ICA stenosis according to preoperative state of DCA and to assess its dynamics after surgery. Thirty-five patients with severe ICA stenosis having different clinical type of disease underwent reconstructive surgery. DCA was assessed with transfer function analysis (TFA) by calculating phase shift (PS) between Mayer waves of blood flow velocity (BFV) and blood pressure (BP) before and after operation ...
An experimental smartphone app might be an effective alternative to a traditional method of assessing circulation in people who need surgery to restore normal blood flow to the heart, a small study suggests.
The main reason for improvement or disappearance of peristent ulceration is considered to be due to clot formation outside the stent. This is promoted by stasis of the blood flow in the space between the stent and the irregular surface of the ulcer, because the stent struts decrease the blood flow into and out of the space. In addition, clot formation outside a stent is also accelerated by the decreasing of turbulent flow due to the decreased and normalized blood flow velocity at the stenotic lesion by stent placement.13-15 Neointimal hyperplasia and continuous expansion of a stent after stent placement may have the effect of curing ulcers in cases of small or shallow ulceration.. Ischemic stroke might be expected due to peristent ulceration because carotid plaque surface irregularity is considered to be one of the risk factors for microemboli, which may subsequently cause ipsilateral ischemic symptoms.8 Rothwell et al studied 3007 patients with carotid plaques in the European Carotid Study ...
TY - GEN. T1 - Efficient focusing scheme for transverse velocity estimation using cross-correlation. AU - Jensen, Jørgen Arendt. PY - 2001. Y1 - 2001. N2 - The blood velocity can be estimated by cross-correlation of received RE signals, but only the velocity component along the beam direction is found. A previous paper showed that the complete velocity vector can be estimated, if received signals are focused along lines parallel to the direction of the flow. Here a weakly focused transmit field was used along with a simple delay-sum beamformer. A modified method for performing the focusing by employing a special calculation of the delays is introduced, so that a focused emission can be used. The velocity estimation was studied through extensive simulations with Field II. A 64-elements, 5 MHz linear array was used. A parabolic velocity profile with a peak velocity of 0.5 m/s was considered for different angles between the flow and the ultrasound beam and for different emit foci. At 60 degrees ...
In spectral Doppler mode, the sample volume is placed at the end of the valvular funnel so as to minimize valvular noise and optimize the recording of blood flow. • Fig. 2-10 Spectral pulsed wave Doppler of the transaortic blood flow obtained from a left apical 5 chambers view by placing the sample volume at the level of the aortic valve. Note the asymmetry of the flow with a short acceleration time. Measurements include the maximal flow velocity (Vmax); the maximal (peak) pressure gradient (peakPG); the area under the curve, or the velocity-time integral (VTI), allowing the calculation of the mean pressure gradient (meanPG); and ejection time (ET). The aortic ratio is frequently used to describe the dimensions of the left atrium. Views Several views may be used to study the aorta and the left atrium (LA): the right parasternal long axis 5 and 4 chambers and the right parasternal short axis transaortic views. Right Parasternal Long Axis 5 Chambers View This view allows the measurements in TM ...
Cerebral autoregulation is a complex physiological process composed of both fast and slow components that may respond differently to different rates and patterns of blood pressure variation. To assess the temporal nature of autoregulation, transcranial Doppler velocity recordings of the middle cereb …
Authors:Connolly M, He X, Gonzalez N, Vespa P, Distefano J 3rd, Hu X.. Due to the inaccessibility of the cranial vault, it is difficult to study cerebral blood flow dynamics directly. A mathematical model can be useful to study these dynamics. The model presented here is a novel combination of a one-dimensional fluid flow model representing the major vessels of the circle of Willis (CoW), with six individually parameterized auto-regulatory models of the distal vascular beds. This model has the unique ability to simulate high temporal resolution flow and velocity waveforms, amenable to pulse-waveform analysis, as well as sophisticated phenomena such as auto-regulation. Previous work with human patients has shown that vasodilation induced by CO2 inhalation causes 12 consistent pulse-waveform changes as measured by the morphological clustering and analysis of intracranial pressure algorithm. To validate this model, we simulated vasodilation and successfully reproduced 9 out of the 12 pulse-waveform ...
Authors:Connolly M, He X, Gonzalez N, Vespa P, Distefano J 3rd, Hu X.. Due to the inaccessibility of the cranial vault, it is difficult to study cerebral blood flow dynamics directly. A mathematical model can be useful to study these dynamics. The model presented here is a novel combination of a one-dimensional fluid flow model representing the major vessels of the circle of Willis (CoW), with six individually parameterized auto-regulatory models of the distal vascular beds. This model has the unique ability to simulate high temporal resolution flow and velocity waveforms, amenable to pulse-waveform analysis, as well as sophisticated phenomena such as auto-regulation. Previous work with human patients has shown that vasodilation induced by CO2 inhalation causes 12 consistent pulse-waveform changes as measured by the morphological clustering and analysis of intracranial pressure algorithm. To validate this model, we simulated vasodilation and successfully reproduced 9 out of the 12 pulse-waveform ...
TY - JOUR. T1 - In Vitro verification of multiple-receiver doppler ultrasound for velocity estimation improvement. AU - Hallac, Rami R.. AU - Agarwal, Mangilal. AU - Jones, Steven A.. PY - 2010/6/1. Y1 - 2010/6/1. N2 - The coherent scattering effect, which introduces noise in Doppler-derived velocity estimates, is caused by constructive and destructive interference of sound waves scattered from multiple particles. Because the phase relationship between signals scattered from different particles depends on the orientation of the receiver, the error in a given velocity estimate depends on the receiver location. To examine this dependence, the velocity of a steady uniform flow was measured simultaneously with a transceiver and three receivers, and the cross-correlation coefficients between velocity estimates for pairs of crystals were calculated. The velocity estimates were nearly independent, with cross-correlation coefficients of approximately 0.2. This result agrees with our previously published ...
An epicardial multifunctional probe has been designed to measure blood flow velocity and muscle thickening with two sensors. The probe is implantable and remains inside the patient after surgery. The probe is removable through a small opening in the patients chest.
Correlation between aortic velocity time integral (AoVTI) at Adaptive CRT and echo-optimized device settings (AoVTI is an echocardiographic representative of stroke volume and cardiac performance ...
Level of Blood Flow  The normal blood flow to the brain is about 50 mL/100g of brain tissue/min.  Ischemic penumbra is a blood flow of 25 mL/100g of brain tissue/min. This level is dangerously low and can lead to loss of brain cells.  A blood flow of 8 mL/100g of brain tissue/min leads to an almost complete loss of functional neurons.  Consciousness is lost within 10 seconds of cessation of blood supply to the brain. Dr. Michael P. Gillespie 3
Color flow mapping has become an important clinical tool, for diagnosing a wide range of vascular diseases. Only the velocity component along the ultrasonic beam is estimated, so to find the actual blood velocity, the beam to flow angle has to be known. Because of the unpredictable nature of vascular hemodynamics, the flow angle cannot easily be found as the angle is temporally and spatially variant. Additionally the precision of traditional methods is severely lowered for high flow angles, and they breakdown for a purely transverse flow. To overcome these problems we propose a new method for estimating the transverse velocity component. The method measures the transverse velocity component by estimating the transit time of the blood between two parallel lines beamformed in receive. The method has been investigated using simulations performed with Field II. Using 15 emissions per estimate, a standard deviation of 1.64% and a bias of 1.13% are obtained for a beam to flow angle of 90 degrees. ...
For example, doctors usually determine whether the heart is pumping enough blood through the primary arteries to end organs by taking an ultrasound measurement called Velocity Time Integral (VTI). Hardware with AI-enabled features, such as Venue and Venue Go, developed by GE Healthcare, can get that VTI reading in seconds, not minutes. Thats because once physicians have an image of the patients beating heart, they can tap a button on the screen (Auto VTI) and the system will automatically place a box where the organs left ventricle meets the aorta, the bodys main artery. (The sample box looks similar to the frame that pops up over peoples faces when you take a photo on a smartphone.). Algorithms do the rest. Within seconds, they can analyze the outlined waveform showing the readings for the rate of blood flow in meters per second, and its volume in liters per minute. The technology dramatically reduces the number of keystrokes and the time it would take to calculate the flow rate manually. ...
How to Treat Shock. Shock is a life-threatening medical emergency caused by interruption of the normal blood flow, which cuts off the supply of oxygen and nutrients to cells and organs. Immediate emergency medical treatment is required....
Pitching velocity secrets from the pros. There are actually many of posts on the internet titled something similar to this article, most of them are useless, given that they focus primarily on upper body mechanics as the only methods to developing velocity. Any hard thrower will show you, there is a lot more to velocity…
This apparatus allow the study of different methods of flow measurement in an incompressible fluid. This a direct application of the steady flow energy equation ; Bernoullis theorem.
Doppler Measurements & Calculations: MV E max vel: 83 cm/sec, MV A max vel: 86 cm/sec, MV E/A:0.96, MV dec time: 0.24 sec, Ao V2 max: 136cm/sec, Ao max PG: 7.0mmHg, LV max PG:3.0mmHg, LV V1 max:90 cm/sec, TR max vel: 204 cm/sec, TR max PG:17 mmHg,RVSPC(TR):22mmHg, RAP systole:5.0 ...
However, that all may be about to change. Blogger and macro specialist Naufal Sanaullah made an interesting observation recently: the United States economy looks like it is finally escaping its liquidity trap, thanks in large part to the stabilization in U.S. housing prices. Sanaullahs basic argument can be summed up in his thesis (emphasis added): Although deleveragings and liquidity traps are inextricably linked, sufficient income growth and credit velocity can allow for the economy to leave the liquidity trap, even as it continues to deleverage (through the denominators impact). This allows for a virtuous cycle to return, as traditional monetary policy regains efficacy and feeds into aggregate demand growth.. In other words, although the economy still has more to delever (reduce debt levels relative to GDP), the deleveraging process may now be helped along by monetary policy, instead of the two forces continuing to work in opposition to each other. To really understand what is going on ...
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At TechnosAmigos.com we go through detailed Qiku N4S vs ZTE Axon 7 Comparison in terms of device specifications, features & price.
OBJECTIVE: To apply a new non-invasive method for quantification of in vivo wall shear stress (WSS) by magnetic resonance (MR) FAcE velocity mapping and measure WSS in the human abdominal aorta. DESIGN: Prospective, open study. MATERIAL: Six voluntee
TY - JOUR. T1 - Breath-hold MR measurements of blood flow velocity in internal mammary arteries and coronary artery bypass grafts. AU - Sakuma, Hajime. AU - Globits, Sebastian. AU - OSullivan, Margaret. AU - Shimakawa, Ann. AU - Bernstein, Matthew A. AU - Foo, Thomas K F. AU - Amidon, Thomas M.. AU - Takeda, Kan. AU - Nakagawa, Tsuyoshi. AU - Higgins, Charles B.. PY - 1996/1. Y1 - 1996/1. N2 - Breath-hold velocity-encoded cine MR (VENC-MR) imaging is a feasible method for measuring phasic blood flow velocity in small vessels that move during respiration. The purposes of the current study are to compare breathhold VENC-MR measurements of flow velocities in the internal mammary arteries (IMA) with nonbreath-hold measurements and to characterize the systolic and diastolic flow velocity curves in a cardiac cycle in native IMA and IMA grafts. Flow velocity in 30 native IMA and 8 IMA grafts were evaluated with a breath-hold VENC-MR sequence with K-space segmentation and view-sharing ...
Coronary flow velocity reserve (CFVR) measured by transthoracic Doppler echocardiography of the LAD is used to assess microvascular function but validation studies in clinical settings are lacking. We aimed to assess feasibility, reproducibility and agreement with myocardial flow reserve (MFR) measured by PET in overweight and obese patients. Participants with revascularized coronary artery disease were examined by CFVR. Subgroups were examined by repeated CFVR (reproducibility) or Rubidium-82-PET (agreement). To account for time variation, results were computed for scans performed within a week (1-week) and for all scans regardless of time gap (total) and to account for scar tissue for patients with and without previous myocardial infarction (MI). Eighty-six patients with median BMI 30.9 (IQR 29.4-32.9) kg × m−2 and CFVR 2.29 (1.90-2.63) were included. CFVR was feasible in 83 (97 %) using a contrast agent in 14 %. For reproducibility overall (n = 21) limits of agreement (LOA) were (−0.75;0.71),
Previous reports have indicated that hypertensive patients who have angina-like chest pain and normal coronary arteriograms have reduced coronary flow velocity reserve (CFVR) levels. In addition, elevated plasma endothelin-1 (ET-1) levels have been reported to be associated with microvascular angina. The purpose of this study was to evaluate the plasma ET-1 levels and CFVR in patients with chest pain but without coronary artery disease (CAD). A total of 66 patients were included in this study. CAD was ruled out by exercise stress test or coronary angiogram. Plasma ET-1 and CFVR measurements were performed in patients with (n=35) and without (n=31) a history of angina-like chest pain. CFVR was measured using adenosine-triphosphate stress transthoracic Doppler echocardiography. The mean ET-1 level was significantly higher and the CFVR was significantly lower in patients in the symptomatic group than in those in the asymptomatic group (ET-1: 3.85±1.24 pg/ml vs. 2.98±1.27 pg/ml, CFVR: 2.26±0.48 vs. 2.77
KP Hanretty, MJ Whittle, PC Rubin; Influence of Atenolol on Human Umbilical and Uteroplacental Doppler Flow Velocity Waveforms. Clin Sci (Lond) 1 January 1988; 74 (s18): 64P. doi: https://doi.org/10.1042/cs074064Pa. Download citation file:. ...
We investigated the effect of acute hypoxia (AH) on dynamic cerebral autoregulation (CA) using two independent assessment techniques to clarify previous, conflicting reports. Twelve healthy volunteers (6 men, 6 women) performed six classic leg cuff tests, three breathing normoxic (Fi(O2) = 0.21) and three breathing hypoxic (Fi(O2) = 0.12) gas, using a single blinded, Latin squares design with 5-min washout between trials. Continuous measurements of middle cerebral artery blood flow velocity (CBFv; DWL MultiDop X2) and radial artery blood pressure (ABP; Colin 7000) were recorded in the supine position during a single experimental session. Autoregulation index (ARI) scores were calculated using the model of Tiecks et al. (Tiecks FP, Lam AM, Aaslid R, Newell DW. Stroke 26: 1014-1019, 1995) from ABP and CBFv changes following rapid cuff deflation (cuff ARI) and from ABP to CBFv transfer function, impulse, and step responses (TFA ARI) obtained during a 4-min period prior to cuff inflation. A new ...
Recently, short-term visual deprivation has been shown to affect a variety of non-visual processes and regional cortical activity (Sathian & Zangaladze, 2001). Surprisingly, very little is known about how such visual deprivation impacts regional cerebral blood flow velocity (CBFv) or its adaptation with the underlying neuronal activity (i.e., neurovascular coupling). The current study sought to investigate the effects of short-term (two-hour) visual deprivation on regional CBFv and neurovascular coupling. CBFv (transcranial Doppler ultrasound) was measured concurrently in the posterior cerebral artery (PCA) and the middle cerebral artery (MCA). Neurovascular coupling was assessed using established methods, consisting of two minutes of baseline (eyes closed and reading), five cycles of 40 seconds reading - 20 seconds eyes-closed (primary protocol), and five cycles of 40 seconds eyes-moving - 20 seconds eyes-closed (secondary protocol). Neurovascular coupling, using both protocols, was collected ...
Fifteen patients (median age 8.5 years) with fixed right ventricular outflow tract obstruction were evaluated by two-dimensional echocardiographically directed continuous wave Doppler ultrasound within 24 hours of cardiac catheterization. Pulmonary artery blood velocity measurements were determined from a real time spectral display of pulmonary artery flow profile and converted to pressure drop utilizing a modified Bernoulli equation. Use of both parasternal and subcostal imaging permitted more accurate detection of maximal flow velocity than did use of either approach alone. Gradients estimated from Doppler recordings correlated well with those measured at cardiac catheterization (correlation coefficient= 0.95, standard error of the estimate = 7.9 mm Hg) with a trend to slight underestimation of gradient in more severe obstruction. In three patients with combined valvular and subvalvular stenosis and one patient with right ventricular outlet obstruction due totally to a ventricular septal ...
The 102 fetuses diagnosed by ultrasound to be asymmetrically growth-retarded had blood flow velocity waveforms of the umbilical artery studied. Sixty-two cases had normal blood flow, 28 had abnormal blood flow but with present end-diastolic flow, 8 had absent end-diastolic flow, and 4 had reversal of end-diastolic flow. Comparison was made between the blood flow status and other biophysical methods of antenatal surveillance and perinatal outcome. There is a strong correlation between abnormal blood flow and abnormalities detected by other biophysical methods of antenatal surveillance. Our study shows that fetuses with severe blood flow impairment tend to be more severely growth-retarded and to be delivered earlier. Our results also show abnormal blood flow to be associated with a poor perinatal outcome. Those fetuses with severe impairment of blood flow suffered a high incidence of operative delivery for fetal distress, acidosis at birth, perinatal mortality and morbidity. The association ...
TY - JOUR. T1 - The assessment of skin blood flow in peripheral vascular disease by laser Doppler velocimetry. AU - Karanfilian, R. G.. AU - Lynch, T. G.. AU - Lee, B. C.. AU - Long, J. B.. AU - Hobson, R. W.. PY - 1984/12/1. Y1 - 1984/12/1. N2 - The helium-neon laser Doppler (LD) is designed to measure skin blood flow velocity (SBFV). Flow velocity and pulse wave amplitude are expressed in millivolts (mv) relative to a zero-flow reference. The authors have reviewed their initial experience in ten persons (20 limbs) without peripheral vascular disease (PVD, group I) and nine patients (12 limbs) with severe PVD (group II). The finger, palm, great toe, and forehead had a significantly (P , 0.05) greater flow velocity than the plantar and dorsal foot, distal and proximal leg, thigh, chest, arm, and forearm. Baseline and hyperemic SBFV, measured at the great toe, were compared in groups I and II. In group I, the baseline SBFV (mv, mean ± standard error of the mean (SEM) in the great toe was 197 ± ...
Myocardial perfusion imaging (MPI), using single photon emission computed tomography (SPECT) is a validated method for detecting coronary artery disease. Transthoracic Doppler echocardiography (TTDE) of flow at rest and during adenosine provocation has previously been evaluated in selected patient groups. We therefore wanted to compare the diagnostic ability of TTDE in the left anterior descending coronary artery (LAD) to that of MPI in an unselected population of patients with chest pain referred for MPI. Our hypothesis was that TTDE with high accuracy would identify healthy individuals and exclude them from the need for further studies, enabling invasive investigations to be reserved for patients with a high probability of disease. Sixty-nine patients, 44 men and 25 women, age 61 ± 10 years (range 35-82), with a clinical suspicion of stress induced myocardial ischemia, were investigated. TTDE was performed at rest and during adenosine stress for myocardial scintigraphy. We found that coronary flow
article{2286a0f7-5934-41f8-aed8-94b7a8b75a40, abstract = {Recent studies indicate a severely reduced coronary flow reserve (CFR) in neonates with congenital heart disease. The significance of these studies remains debatable, as the ability of the anatomically normal neonatal heart to increase coronary flow is currently unknown. This study was designed to establish normal values for CFR in newborns after administration of adenosine [pharmacologic CFR (pCFR)] and as induced by acute hypoxemia (reactive CFR). Thirteen mechanically ventilated newborn lambs were studied. Coronary flow velocities were measured in the proximal left anterior descending coronary artery before and after adenosine injection (140 and 280 mug/kg i.v.) using an intracoronary 0.014-in Doppler flow-wire. Measurements were made at normal oxygen saturation (Sao(2)) and during progressive hypoxemia induced by lowering the fraction of inspired oxygen. CFR was defined as the ratio of hyperemic to basal average peak flow velocity. In ...
Authors: Kashif FM, Verghese GC, Novak V, Czosnyka M, Heldt T.. Intracranial pressure (ICP) is affected in many neurological conditions. Clinical measurement of pressure on the brain currently requires placing a probe in the cerebrospinal fluid compartment, the brain tissue, or other intracranial space. This invasiveness limits the measurement to critically ill patients. Because ICP is also clinically important in conditions ranging from brain tumors and hydrocephalus to concussions, noninvasive determination of ICP would be desirable. Our model-based approach to continuous estimation and tracking of ICP uses routinely obtainable time-synchronized, noninvasive (or minimally invasive) measurements of peripheral arterial blood pressure and blood flow velocity in the middle cerebral artery (MCA), both at intra-heartbeat resolution. A physiological model of cerebrovascular dynamics provides mathematical constraints that relate the measured waveforms to ICP. Our algorithm produces patient-specific ...
We present adaptive micro-scale Particle Image Velocimetry (μPIV) technique for visualization of the capillary network blood flow microcirculation. The main idea of our method is a centering of the interrogation regions (IR) of the μPIV technique via capillary network masks. These masks were obtained by the algorithm of Niblack local binarization of the capillary network images for the each frame. Due to the inhomogeneous of red blood cells (RBCs) distribution, we have summarized the masks across a whole series of masks. The blood flow velocity map was measured within the limits of the resulting the mask. We illustrate step-by-step the blood flow velocity measurement method and we reconstruct velocity map for chorioallantoic membrane (CAM) of chicken embryo ...
Aortic regurgitation is associated with retrograde diastolic flow in the aorta. Echocardiographic quantitative analysis of the magnitude of the flow reversal is believed to provide an estimate of severity of regurgitant disease despite variations in flow profiles. The purpose of this study was to ev …
Define laser Doppler velocimeter (LDV): Device which determines particle velocity through the measurement of scattered interference of a beam pair fro...
Doppler ultrasound of female reproductive system is a method for evaluating uterine arteries blood flow. Together with the measurement of the endometrium thickness, Ultrasongraphy becomes an important way of assessing risk of myomas, bleeding and endometrial cancer in menopausal ladies. Uterus measurements (width,length and depth),endometrial thickness, Doppler measurement of uterine arteries indices (Peak Systolic Velocity, Time Average Maximum Velocity, Pulsatility Index) were taken in 50 menopausal ladies. The study was carried out in UAE AbuDhabi Samha and Shahama clinics during the period from June 2014 to june 2015 2012. The endometrial thickness, uterine arteries pulstility index , resistance index, Peak Systolic Velocity and Time Average Maximum Velocity,uterus echogenicity were correlated significantly with the mean of average age and posmenpausal age In age of 62 yrs and postmenopausal age of 50 yrs, doppler examination of L&R uterine arteries showed its blood flow velocity waveform ...
To evaluate the haemodynamic changes induced by flow diversion treatment in cerebral aneurysms, resulting in thrombosis or persisting aneurysm patency over time. Eight patients with aneurysms at the para-ophthalmic segment of the internal carotid artery were treated by flow diversion only. The clinical follow-up ranged between 6 days and 12 months. Computational fluid dynamics (CFD) analysis of pre- and post-treatment conditions was performed in all cases. True geometric models of the flow diverter were created and placed over the neck of the aneurysms by using a virtual stent-deployment technique, and the device was simulated as a true physical barrier. Pre- and post-treatment haemodynamics were compared, including mean and maximal velocities, wall-shear stress (WSS) and intra-aneurysmal flow patterns. The CFD study results were then correlated to angiographic follow-up studies. Mean intra-aneurysmal flow velocities and WSS were significantly reduced in all aneurysms. Changes in flow patterns were
To evaluate the accuracy of a pulsed multigated Doppler system, 128 carotid arteries were examined. The spectral broadening index was calculated from the power spectrum of a small sample volume located in the center of the stream according to the flow profile and was related to the degree of stenosis as determined by contrast angiography. Even minor wall irregularities seen on the angiogram were classified as disease. The ability of the system to discriminate between normal and diseased vessels reached a sensitivity of 94% and a specificity of 91%. Classification of greater than 50% or less than 50% stenosis could be performed with a sensitivity of 90% and a specificity of 85%. Pulsed multigated Doppler ultrasonography allows identification of even minor degrees of stenosis of the carotid artery and provides an alternative to duplex scanning. Furthermore, the blood flow profile provided by a multigated Doppler system may add valuable information concerning blood flow characteristics not ...
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This paper analyzes velocity profiles for flow through circular tubes in laminar, turbulent, and transition region flows and how they affect measurement by flow-meters. Experimental measurements of velocity profiles across the cross-section of straight circular tubes were made using laser doppler velocimetry. In addition, flow visualization was done using the hydrogen bubble technique. Velocity profiles in the laminar and the turbulent flow are quite predictable which allow the determination of meter factors for accurate flow measurement. However, the profiles can not be predicted at all in the transition region. Therefore, for the accuracy of the flowmeter, it must be ensured that the flow is completely in the laminar regime or completely in the turbulent regime. In the laminar flow a bend, even at a large distance, affects the meter factor. The paper also discusses some strategies to restructure the flow to avoid the transition region.. ...
Aliasing is associated only with pulsed Doppler, it never appears with continuous wave Doppler. A standard continuous wave Doppler has a receiver and a transmitter. The transmitter produces continuous sound waves which the receiver collects. Both elements are positioned at specific angles from one another enabling the receiver to receive reflected ultrasound waves.. The disadvantage of using a continuous wave Doppler is the range ambiguity. With this technique, velocities along the entire region of overlap between the transmit and receive beams, blend together to form the spectrum. With pulsed Doppler, velocities from blood within the sample volume are measured.. Eliminating aliasing improves the ability to measure the maximum velocity with Doppler.. ...
Biomech Model Mechanobiol. 2013 Jan 1. [Epub ahead of print] Leinan PR, Degroote J, Kiserud T, Skallerud B, Vierendeels J, Hellevik LR. Source Biomechanics Division, Department of Structural Engineering, The Norwegian University of Science and Technology, 7491, Trondheim, Norway, [email protected] Abstract The veins distributing oxygenated blood from the placenta to the fetal body have been given much attention in clinical Doppler velocimetry studies, in particular the ductus venosus. The ductus venosus is embedded in the left liver lobe and connects the intra-abdominal portion of the umbilical vein (IUV) directly to the inferior vena cava, such that oxygenated blood can bypass the liver and flow directly to the fetal heart. In the current work, we have developed a mathematical model to assist the clinical assessment of volumetric flow rate at the inlet of the ductus venosus. With a robust estimate of the velocity profile shape coefficient (VC), the volumetric flow rate may be estimated as ...
TY - JOUR. T1 - Antegrade late diastolic arterial blood flow in the fetus. T2 - Insight into fetal atrial function. AU - Howley, Lisa W.. AU - Yamamoto, Yuka. AU - Sonesson, Sven Erik. AU - Sekar, Priya. AU - Jain, Venu. AU - Motan, Tarek. AU - Savard, Winnie. AU - Wagner, Brandie D.. AU - Trines, Jean. AU - Hornberger, Lisa K.. PY - 2013/6. Y1 - 2013/6. N2 - Objective: The purpose of this study was to examine the presence and frequency of antegrade late diastolic arterial blood flow (ALDAF) in the fetus and to determine its contribution to cardiac output. Study Design: We evaluated the presence of ALDAF in 457 fetal and 21 postnatal echocardiograms. The timing of ALDAF to the ventricular systolic Doppler recording (ALDAF-V) was compared with the mechanical atrioventricular interval and, in neonates, the electrical PR interval. Velocity time integrals of ALDAF and the ventricular systolic Doppler signals were measured, and the percent contribution of ALDAF was calculated. Results: ALDAF was ...
We thank Miller et al. for their interest in the results of our assessment of noninvasive ICP measurement technology. This method is accurate and sensitivity and specificity are much higher compared with other approaches.1,6,7. Blood flow in both segments of the OA depends on ICP, ambulatory blood pressure, heart rate, intraocular pressure, intraorbital pressure, and other factors.1 The benefit of our method is in the equilibration of ICP with Pe. The balance ICP = Pe is not dependent on influential factors. OA blood flow velocities could be very different in different patients1 but the balance ICP = Pe does not depend on the OA blood flow velocity values. As a result, our method does not need a patient-specific calibration. All correlation-based noninvasive ICP measurement approaches cannot be used for absolute ICP value measurements because they need patient-specific calibration, which is impossible.. Our 2-depth transcranial Doppler technology complies with all safety standards. The maximum ...
This study is the first to use the constant routine (CR) protocol to determine whether the endogenous circadian pacemaker contributes to the previously reported diurnal changes in CBFV. The current work demonstrates that, with limited periodic external stimuli and a constant posture, there is 24-hour rhythmicity in CBFV. Subjects showed a cycle of approximately 24 hours in CBT, which has been previously demonstrated with the CR [21].. Figure 3 illustrates the intricate relationship between the rhythms across the study period. At approximately the CBT acrophase, the relationship between the two rhythms undergoes a transition. Between 180 and 240 degrees, CBFV is still rising and CBT is changing directions (first rising, reaching its peak and then falling). This period between 180 and 240 has been described as a wake maintenance zone, a time in the circadian cycle during which humans are less likely to fall asleep [22]. In our subjects, the CBT is near its zenith or just starting to fall at this ...
PURPOSE: To show that 4D Flow is a clinically viable tool for evaluation of collateral blood flow and demonstration of distorted blood flow patterns in patients with treated and untreated aortic coarctation.. MATERIALS AND METHODS: Time-resolved, 3D phase contrast magnetic resonance imaging (MRI) (4D Flow) was used to assess blood flow in the thoracic aorta of 34 individuals: 26 patients with coarctation (22 after surgery or stent placement) and eight healthy volunteers.. RESULTS: Direct comparison of blood flow calculated with 2D and 4D phase contrast data at standard levels for analysis in coarctation patients showed good correlation and agreement (correlation coefficient r = 0.99, limits of agreement = -20% to 20% for collateral blood flow calculations). Abnormal blood flow patterns were demonstrated at peak systole with 4D Flow visualization techniques in the descending thoracic aorta of patients but not volunteers. Marked helical flow was seen in 9 of 13 patients with angulated aortic arch ...
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Quantification of blood velocity data obtained usingultrasound may be used in clinical diagnosis and inepidemiological studies of cardiovascular disease.
Effects of repeated H-Wave device stimulation (HWDS) on blood flow and angiogenesis in the rat hind limb were studied. The hypothesis tested was that HWDS acutely increases hind limb blood flow, and that repeated HWDS would elicit angiogenesis. Animals were HWDS-conditioned (Conditioned) or shamstimulated (Sham) (n D 5/group) daily for 3 weeks. The contralateral limb in both groups served as the control. Each animal was injected with bromodeoxyuridine (BrDU). After 3 weeks, rats were anesthetized and iliac artery blood flow was measured bilaterally before, during, and after acute HWDS. HWDS of the Conditioned limbs elicited a 247% increase in blood flow above resting conditions compared to a 200% increase in control legs. Sham animals did not demonstrate between-leg differences in flow. Hindlimb musculature staining for BrDU revealed angiogenesis in Conditioned versus Sham groups. Flow changes accompanying HWDS corroborated earlier microvascular findings demonstrating a significant ...
3D CINE Phase Contrast Magnetic Resonance Imaging (PCMRI) is considered the technique of election to study in vivo the time varying, complex blood flow structures evolving into arteries [1]. PCMRI allows to obtain a quantitative depiction of the spatial distribution of blood velocities from the acquired phase data and the anatomical image of the district of interest from magnitude data. A major limitation in the application of 3D CINE PCMRI to the clinical practice is the long scan time needed to obtain phase datasets (i.e., blood flow velocities) of sufficient quality for hemodynamic visualizations of time evolving fluid structures or for volumetric flow rates retrospective quantification and analysis. Recently, huge efforts have been done to speed up in vivo acquisitions by implementing/optimizing parallel imaging acquisition schemes as the Sensitivity Encoding (SENSE) [2]. However, the increased reduction factors employed in SENSE scheme to speed up the acquisition lead to acquired PCMRI ...
The authors have been developing a model of blood flow in the heart. The flow model of the heart enables us to estimate the entire blood flow of the heart from a couple of 2-D color Doppler images. Therefore, the load on patients is expected to be reduced. To develop the model of the heart, precise observation and an understanding of the blood flow are indispensable, because the flow is strongly related to the diagnosis of heart diseases. The visualization method must have the following features: (1) 3-D (2) objectivity (3) interactivity and (4) multi-aspect. The authors have developed visualization methods to meet the above-mentioned requirements and evaluated the proposed methods with the in-vitro flow data set. The results clearly reveal that the proposed system enables the researchers of the modeling group to obtain the state of entire flow, such as the occurrence of turbulence.. ...
Doppler optical coherence tomography has the capability to measure blood flow quantitatively and in vivo. As only the axial component of the velocity can be assessed, the measurements have to be corrected for the angle of the vessels. We present a novel approach to extract quantitative flow data from circumpapillary scans in vivo on the human retina by registering the circular scan to a reference volume scan and extracting the angle directly from the volume. In addition, we perform phase unwrapping and interpolation of the flow under the assumption of a parabolic flow profile. We demonstrate the repeatability of the methods by applying it to different retinal vessels, achieving coefficients of variation of the average velocity of 3 to 8%. Results on the pulsatility and resistance index are also presented.. ©2010 Optical Society of America. Full Article , PDF Article ...
To the Editor:. Michelson et al,1 from study of the ophthalmic artery flow pulse in the frequency domain, have noted features that are associated with aging and hypertension, and have the potential to identify early stages of microvascular disease in the eye. The findings concur with our studies of the carotid flow pulse in the time domain, which, likewise, are associated with aging and hypertension2 and have the potential to explain microvascular disease and pulse wave encephalopathy in the brain.3 The common link is early wave reflection from peripheral sites in the lower body, consequent on arterial stiffening; this increases amplitude of the lower harmonics of carotid arterial flow (and pressure) waves and in the time domain is apparent as increase in flow (and pressure) augmentation index.4 The explanation by Michelson et al1 relates to characteristics of the ophthalmic arterys vascular bed. We believe that this is unlikely, and note the evidence of similar and low-resistance index in ...
Blended Introduction to Carotid Duplex/Color Flow Imaging & Transcranial Doppler Ultrasound Course is taught by leading vascular ultrasound experts and offers fifteen (15) months unlimited access to the online courses, plus two (2) days/16 hours scan lab with a 3:1 faculty to participant hands-on scan ratio at our facility in St. Petersburg, FL.
Private Hands-On Introduction to Transcranial Doppler Ultrasound Training Course is designed to provide a strong foundation to perform and/or interpret Transcranial Doppler and Transcranial color flow imaging examinations.
Nonuniform lateral scanning of the probe beam in optical coherence tomography produces imaging artifacts and leads to a morphologically inaccurate representation of the sample. Here, we demonstrate a solution to this problem, which is based on the Doppler shift carried by the complex-valued depth-resolved scattering amplitude. Furthermore, we demonstrate the feasibility of Doppler flow velocity measurements in underlying flow channels while laterally scanning the imaging probe over large surfaces with arbitrary and varying velocity. Finally, we performed centimeters-long hand-held B-mode imaging of skin in vivo.. ©2012 Optical Society of America. Full Article , PDF Article ...
Although crucial in regulating intracranial hydrodynamics, the cerebral venous system has been rarely studied because of its structural complexity and individual variations. The purpose of our study was to evaluate the organization of cerebral venous system in healthy adults. Phase-contrast magnetic resonance imaging (PC-MRI) was performed in 18 healthy volunteers, in the supine position. Venous, arterial, and cerebrospinal fluid (CSF) flows were calculated. We found heterogeneous individual venous flows and variable side dominance in paired veins and sinuses. In some participants, the accessory epidural drainage preponderated over the habitually dominant jugular outflow. The PC-MRI enabled measurements of venous flows in superior sagittal (SSS), SRS (straight), and TS (transverse) sinuses with excellent detection rates. Pulsatility index for both intracranial (SSS) and cervical (mainly jugular) levels showed a significant increase in pulsatile blood flow in jugular veins as compared with that ...
Intracranial pressure (ICP) and continuous transcranial Doppler ultrasound signals were monitored in 20 head-injured patients and simultaneous synchronous fluctuations of middle cerebral artery (MCA) velocity and B waves of the ICP were observed. Continuous simultaneous monitoring of MCA velocity, ICP, arterial blood pressure, and expired CO2 revealed that both velocity waves and B waves occurred despite a constant CO2 concentration in ventilated patients and were usually not accompanied by fluctuations in the arterial blood pressure. Additional recordings from the extracranial carotid artery during the ICP B waves revealed similar synchronous fluctuations in the velocity of this artery, strongly supporting the hypothesis that blood flow fluctuations produce the velocity waves. The ratio between ICP wave amplitude and velocity wave amplitude was highly correlated to the ICP (r = 0.81, p , 0.001). Velocity waves of similar characteristics and frequency, but usually of shorter duration, were ...
博士論文. Recently, quantitative flow visualization has become an important tool to investigate three-dimensional complex flow structures in microfluidic. The development of laser, computer and digital image processing techniques made it possible to extract velocity field information from visualized flow images of tracer particles. Particle image velocimetry (PIV) / particle tracking velocimetry (PTV) method has become one of the most useful flow diagnostic technologies in the modern history of fluid mechanics. The particle based velocimetry techniques measure the whole velocity field information in a plane by dividing that is placements Δx and Δy of tracer particles with the time interval Δt during which the particles were displaced. Since the flow velocity is inferred from the particle displacement, it is also important to select proper tracer particles that follow the flow motion accurately without changing the flow properties. These methods have been accepted as a reliable and ...
Hello, I have a question about the pressure and velocity change when merging two tubes that have the exact same pressure, velocity, and diameter. Ive attached an image to give you guys a visualization. Say the three tubes are all laying flat on the ground, so theres no height change ...
In: McDonald's Blood Flow in Arteries: Theoretical, Experimental and Clinical Principles. 4th ed. London, UK: Edward Arnold; ... The speed of travel of this pulse wave (pulse wave velocity (PWV)) is related to the stiffness of the arteries. Other terms ... Wilmer W. Nichols; Michael F. O'Rourke (25 February 2005). McDonald's Blood Flow in Arteries 5Ed: Theoretical, experimental and ... The increase in pulse pressure may result in increased damage to blood vessels in target organs such as the brain or kidneys. ...
As the blood moves into the aortic arch, the area with the highest velocity tends to be on the inner wall. Helical flow within ... Some simplified flows include plug flow, parabolic flow, linear shear flow, and skewed cubic flow. 1D and 3D flows generated ... 1D flows include the patient-specific variation of velocity normal to inlet. 3D flows include patient-specific velocities in ... At this stage the majority of the flow can be described with velocity vectors normal to the entrance, but in plane velocities ...
Velocity selective arterial spin labelling is advantageous in a population where blood flow may be impeded (e.g stroke), ... which does not directly correlate with blood flow. Cerebral blood flow on the other hand does, allowing for cardiovascular ... is a magnetic resonance imaging technique used to quantify cerebral blood perfusion by labelling blood water as it flows ... In continuous arterial spin labelling (CASL), the blood water is inverted as it flows through the brain in one plane. CASL is ...
Once the desired blood vessel is found, blood flow velocities may be measured with a pulsed Doppler effect probe, which graphs ... are types of Doppler ultrasonography that measure the velocity of blood flow through the brain's blood vessels by measuring the ... Although TCD is not so accurate due to relative velocity of blood flow, but it is still useful for diagnosis of arterial ... Blood flow velocity measurements are robust against movement artifacts. Since its introduction the technique has contributed ...
... increased portal blood flow) Splenomegaly and/or hypersplenism (increased portal blood flow) Hepatic causes Cirrhosis of any ... a slow velocity of ... endogenous vasodilators in turn promote more blood flow in the ... Portal hypertension is abnormally increased portal venous pressure - blood pressure in the portal vein and its branches, that ...
This allows assessment of both normal and abnormal blood flow through the heart. Color Doppler, as well as spectral Doppler, is ... The Doppler technique can also be used for tissue motion and velocity measurement, by tissue Doppler echocardiography. ... This is commonly used to measure the size of blood vessels and to measure the internal diameter of the blood vessel. For ... but it can also produce accurate assessment of the blood flowing through the heart by Doppler echocardiography, using pulsed- ...
... is used to measure flow velocities in the body. It is used mainly to measure blood flow in the heart and throughout the body. ... or weighting the MRI signal by cerebral blood flow (CBF) and cerebral blood volume (CBV). The CBV method requires injection of ... blood flow), MTT (mean transit time) and TTP (time to peak). In cerebral infarction, the penumbra has decreased perfusion. ... In biological tissues however, where the Reynolds number is low enough for laminar flow, the diffusion may be anisotropic. For ...
Increased blood pressure will have an effect on cerebral blood flow, cerebral blood flow velocity and intracranial pressure. ... Increased pressures and velocity can lead to intracranial hemmorrhage. Prolonged exhalation may also cause some adverse effects ... The cortisol levels will rise along with blood pressure. ...
By assessing the velocity of blood flow, the doctors can measure whether the kidney is receiving enough blood and nutrients to ... Ultrasound is combined with doppler, to locate and assess the renal artery and the velocity of blood flowing through it. This ... Blood vessels shrink and undergo apoptosis which results in poor blood flow in the kidneys. More complications happen when ... Because the blood vessels carry oxygen and nutrients throughout the body, having atherosclerosis restrict blood flow and ...
... ejection time or flow time), the average aortic blood velocity is calculated. The product of average velocity and ejection time ... It usually displays a graph of real-time aortic blood velocities and recognized main flow against time. It provides ... This list is analysed to identify the velocities of the plug flow like movement down the centre of the aorta. The plug flow ... Flow time (FT) is the time difference between the sudden increase in velocity (T0) and the return to near zero velocity (T1). ...
This is combined with removal of the celiac ganglia and evaluation of blood flow through the celiac artery, for example by ... Peak systolic velocities greater than 200 cm/s are suggestive of celiac artery stenosis associated with MALS. Further ... If blood flow is poor, celiac artery revascularization is usually attempted; methods of revascularization include aortoceliac ... One proposes that compression of the celiac artery causes ischemia, or decreased blood flow, to abdominal organs, leading to ...
Vascular malformations can cause abnormal blood flow to areas of the brain. If too little blood is delivered to the basal ... This decreases the conduction velocity of the neurons, making the signals received by the basal ganglia garbled and incomplete ... A stroke causes tissue to die due to a lack of oxygen resulting from an impaired blood supply. In the basal ganglia, this can ... Also in chorea the movements are more dance-like, flowing from one region to another. Ballism was defined by Meyers in 1968 as ...
Blood vessels act as compliant tubes that change size dynamically when there are changes to blood pressure and velocity of flow ... J.-F. Gerbeau; M. Vidrascu; P. Frey (2005). "Fluid-structure interaction in blood flows on geometries based on medical imaging ... Fluid-structure interactions also play a major role in appropriate modeling of blood flow. ... "A quasi-Newton algorithm based on a reduced model for fluid-structure interaction problems in blood flows" (PDF). ESAIM: ...
J Cereb Blood Flow Metab 30(2):255-266. Pelley, Scott "How IEDs may be physically causing PTSD"; 60 Minutes, 1 April 2018. ... which displaces an equal volume of air at a very high velocity. The velocity of the blast wave in air may be extremely high, ... At times the propelled object may become embedded in the body, obstructing the loss of blood to the outside. However, there may ... Additionally, the intensity of the pressure changes from the blast can cause injury to the blood vessels and neural pathways ...
Schmidt, LE; Svendsen, LB; Sørensen, VR; Hansen, BA; Larsen, FS (August 2001). "Cerebral blood flow velocity increases during a ... A catheter removes blood from the patient, and an ultrafiltrate generator separates the plasma from the rest of the blood. This ... administration Uncontrolled hemorrhage Severe coagulopathy Severe thrombocytopenia Blood Flow The trend is to use high flow ... The primary functions of the liver include removing toxic substances from the blood, manufacturing blood proteins, storing ...
... measure the velocity of blood flow through the brain's blood vessels transcranially (through the cranium). These modes of ... produce an accurate assessment of the direction of blood flow and the velocity of blood and cardiac tissue at any arbitrary ... from blood flowing away from the transducer and blue representing the shorter wavelengths from blood flowing toward the ... One of the limitations is that the ultrasound beam should be as parallel to the blood flow as possible. Velocity measurements ...
... supraperiosteal dissection or other techniques to maintain the periosteal blood flow. In high velocity injuries, the soft ... addition risks apply because the blood flow from the marrow (endosseous) is minimal and the healing bone must rely on blood ... the jaw loses its endosteal blood supply. Instead, the blood supply comes largely from the periosteum. Open reduction (which ... High velocity injuries (e.g. those caused by bullets, improvised explosive devices, etc...) will frequently cause comminuted ...
It is believed to be caused primarily by the incorrect adjustment of the tandem harness affecting blood flow. This rarely ... terminal velocity. This is necessary for proper parachute deployment, lengthening the duration of the skydive, and allowing the ...
A blood flow velocity of more than 120 centimeters per second is suggestive of vasospasm. The use of calcium channel blockers, ... Vasospasm, in which the blood vessels constrict and thus restrict blood flow, is a serious complication of SAH. It can cause ... In people with aneurysmal subarachnoid hemorrhage the EVD is used to remove cerebrospinal fluid, blood, and blood byproducts ... high blood pressure), hypervolemia (excess fluid in the circulation), and hemodilution (mild dilution of the blood). Evidence ...
The pelvis and legs get their blood from the common iliac arteries. The pulsatile nature of blood flow creates a pulse wave ... Maximum aortic velocity may be noted as Vmax or less commonly as AoVmax. Mean arterial pressure (MAP) is highest in the aorta, ... Another system divides the aorta with respect to its course and the direction of blood flow. In this system, the aorta starts ... McDonald's Blood Flow in Arteries: Theoretical, Experimental and Clinical Principles. 4th ed. London, UK: Edward Arnold; 1998 ...
... blood}}} is the blood velocity. If blood water flows without changing direction (either because flow is slow or measurement ... blood}}} , the diffusion coefficient of water in blood: D ∗ = L . v blood / 6 + D blood {\displaystyle D^{*}=L.v_{\text{blood ... method of blood flow measurement to changes in cerebral blood flow". Magnetic Resonance in Medicine. 32 (1): 60-5. doi:10.1002/ ... It is responsible for a signal attenuation in diffusion MRI, which depends on the velocity of the flowing blood and the ...
A similar correlative study was performed during the Cosmos 1514 mission, where blood flow velocity was compared to total body ... The main objective of American participation in the Kosmos 1667 mission was to measure carotid artery pressure and blood flow ... Instrument calibration procedures were modified on this mission to ensure that blood pressure measurements would be accurate. ...
... produce accurate assessment of the direction of blood flow and the velocity of blood and cardiac tissue at any arbitrary point ... A blood flow study is done prior to the injection, by power doppler. The blood flow can be destroyed and the node become ... which measure the velocity of blood flow through the brain's blood vessels transcranially (through the cranium). They are used ... By using pulsed wave Doppler or continuous wave Doppler blood flow velocities can be calculated. Figures released for the ...
This uses inexpensive microfluidics such that as the blood flows through the channels, its progress and therefore velocity, is ... The nano-cytometer aims to make disease detection easier and cheaper at home by testing a single drop of blood using a ...
Changing flow velocity impacts the value of the standard deviation. When the difference in flow velocity becomes larger, the ... especially for imaging in vivo blood flow, OCT has become a popular research topic recently. Not only conserving the excellence ... Fluid flow velocity can be calculated as: V O D T ( i ) = λ 0 f D 2 n c o s θ = λ 0 ( f c − f o ) 2 n c o s θ ( 6 ) {\ ... In 1991, the first use of coherence gating to localized flow velocity was reported. The author of that article measured the 1- ...
... the mean blood velocity index v ¯ {\displaystyle {\bar {v}}} FT (measured in s−1 during flow time, and FT (flow time measured ... the pulsatile blood flow forces the red blood cells to align in parallel with the blood flow. When the electric current is then ... The higher the mean blood velocity during flow time, the more SV the left ventricle ejects. The 'volume of electrically ... Prior to opening of the aortic valve, the red blood cells (erythrocytes) assume a random orientation (there is no blood flow in ...
Its first products tracked the heart rate and blood flow of air force pilots and astronauts, by embedding sensors in their ... Algorithms integrate the pilot's physiology, aircraft physics (G-forces, velocity, altitude & positioning) and the pilot's head ... The optical technology is integrated into Elbit's smart helmets for F-16 pilots, released in June 2015, measuring blood flow ( ... LifeBEAM technology is integrated into a helmet for pilots developed by Elbit that measures blood flow (including oxygen ...
Experimental velocity profiles and volumetric flow via two-dimensional speckle tracking. Ultrasound Med Biol. 1995;21(7):885-98 ... A novel method for angle independent ultrasonic imaging of blood flow and tissue motion. IEEE Trans Biomed Eng. 1991 Mar;38(3): ... giving a velocity field with velocity vectors along the ultrasound beam over the whole sector. It measures the velocity ... This is thus equivalent to the velocity difference per length unit (the spatial derivative of velocity) and has the unit s−1. ...
Effects of sensory modality on cerebral blood flow velocity during vigilance, Neuroscience Letters 461, 207-211 Steriade, M. ( ... These neuroimaging techniques estimate brain activation by measuring the blood flow (fMRI and TCD) or glucose metabolism (PET) ...
"Automatic Tracing of Blood Flow Velocity in Ultrasound Doppler Images" by Zhe Wang (Doctoral student), April 2008. 2007: Chang ...
Sedimentation Velocity Analysis of Heterogeneous Protein-Protein Interactions: Lamm Equation Modeling and Sedimentation ... Separation of urine components and blood components in forensic and research laboratories ... ultracentrifuges can separate molecules in batch or continuous flow systems. ... 6] the applied centrifugation field is square angular velocity in radians per sec .the radial distance o the particle from the ...
Early chiropractors believed that all disease was caused by interruptions in the flow of innate intelligence, a vitalistic ... high blood pressure, and vision conditions.[123] Other reviews have found no evidence of significant benefit for asthma,[124][ ... High-velocity, low-amplitude spinal manipulation (HVLA-SM) thrusts have physiological effects that signal neural discharge from ...
The limiting case of the Venturi effect is when a fluid reaches the state of choked flow, where the fluid velocity approaches ... which obstructs blood flow, which leads to a pulsus bisferiens. ... such as the flow of water or other liquid, or low speed flow of ... Flow rate[edit]. A venturi can be used to measure the volumetric flow rate, Q. {\displaystyle \scriptstyle Q}. . ... Increasing source temperature will also increase the local sonic velocity, thus allowing for increased mass flow rate but only ...
They found that as these chills increase, many changes in cerebral blood flow are seen in brain regions such as the amygdala, ... velocity and acceleration).[18] ... investigated cerebral blood flow (CBF) changes related to ... used PET to measure changes in cerebral blood flow while participants listened to music that they knew to give them the "chills ... was utilized to measure cerebral blood flow (CBF) in musicians possessing AP and musicians lacking AP. When presented with ...
"Morbidity & Mortality: 2009 Chart Book on Cardiovascular, Lung, and Blood Diseases" (PDF). National Heart, Lung, and Blood ... The greatest reduction in air flow occurs when breathing out, as the pressure in the chest is compressing the airways at this ... the use of low amplitude high velocity joint mobilization together with exercise improves lung function and exercise capacity.[ ... A chest X-ray and complete blood count may be useful to exclude other conditions at the time of diagnosis.[80] Characteristic ...
He received the Nobel Prize in Chemistry in 1909 for his work on catalysis, chemical equilibria and reaction velocities. He, ... Another area where he "goes against the flow" is in his spiritual beliefs. As far as religion is concerned, he's a confirmed ... Crile is now formally recognized as the first surgeon to have succeeded in a direct blood transfusion.[85] ...
... to indirectly calculate flow. Flow may be measured by measuring the velocity of fluid over a known area. For very large flows, ... For example, ultrasonic flowmeters are used for the measurement of such diverse fluids as liquid natural gas (LNG) and blood.[ ... Such flow is called viscous drag flow or laminar flow, as opposed to the turbulent flow measured by orifice plates, Venturis ... Area/velocity[edit]. The cross-sectional area of the flow is calculated from a depth measurement and the average velocity of ...
... have faster blood flow, and would get diluted as it is quickly distributed to the rest of the body. Vasopressors (such as ... Hirschfeld S, Hyman HT, Wanger JJ (February 1931). "Influence of velocity on the response to intravenous injections". Archives ... Further information: Blood product, Blood transfusion, and Blood substitute. A blood product (or blood-based product) is any ... Early blood transfusions consisted of whole blood, but modern medical practice commonly uses only components of the blood, such ...
... and blood glucose. The real-time delivery of blood glucose and blood pressure readings enables immediate alerts for patient and ... The continuous flow of patient data requires a dedicated team of health care providers to handle the information, which may, in ... linear acceleration and angular velocity, and utilize a mathematical algorithm to predict the likelihood for falls, detect ... Examples of peripheral devices are: blood pressure cuff, pulse oximeter, and glucometer. The data are transmitted to healthcare ...
The [CGS] electromagnetic unit of current is that current, flowing in an arc 1 cm long of a circle 1 cm in radius, that creates ... Similarly, the millimetre of mercury (symbol mmHg) was retained for measuring blood pressure.[3]:127. ... velocity is a quantity that is derived from the base quantities of time and length, and thus the SI derived unit is metre per ... Sphygmomanometer - the traditional device that measures blood pressure using mercury in a manometer. Pressures are recorded in ...
The ostrich reduces blood flow to the trachea to cool itself, and vasodilates its blood vessels around the gular region to ... ostrich respiration can be thought of as a high velocity-low pressure system.[62] At rest, there is small pressure differences ... the red blood cells of the ostrich are about three times larger than the red blood cells of a human.[72] The blood oxygen ... The advantage of this thick barrier may be protection from damage by large volumes of blood flow in times of activity, such as ...
... be estimated from the TCD measurements because it impedes the blood flow and consequently decreases the velocity of blood flow ... The TCD measures the velocity of blood flow through the major intracranial vessels by emitting a high frequency (,2MHz) wave ... The Cerepress™ measures blood pressure in the eye's central retinal vein (CRV) and blood velocity in the ophthalmic artery, ... Blood flow in the intracranial OA segment is affected by intracranial pressure, while flow in the extracranial (intraorbital) ...
In addition, atherosclerosis can constrict blood flow.[61][65]. *Immune function. Less efficient immune function ( ... Gait velocity slows after age 70. Double stance time (i.e., time with both feet on the ground) also increases with age. Because ...
A heart valve normally allows blood to flow in only one direction through the heart. The four valves are commonly represented ... u = axial velocity. p = pressure. A = cross sectional area of valve. L = axial length of valve. Λ(t) = single degree of freedom ... across an open heart valve relates to the flow rate, Q, through the valve: a. ∂. Q. ∂. t. +. b. Q. 2. =. Δ. p. {\displaystyle a ... The valves incorporate leaflets or cusps, which are pushed open to allow blood flow and which then close together to seal and ...
"Thermal Fluctuations of Red Blood Cell Membrane via a Constant-Area Particle-Dynamics Model". Biophysical Journal. 89 (4): ...
Besides surrounding each fascicle, the perimysium is a pathway for nerves and the flow of blood within the muscle. The ... would result in decreased force but increased velocity. This can be most easily seen by comparing the limb of a mole to a horse ... The heart, liver and red blood cells will also consume lactic acid produced and excreted by skeletal muscles during exercise. ... Diagnostic procedures that may reveal muscular disorders include testing creatine kinase levels in the blood and ...
Flow, fluid velocity. *Air flow meter. *Anemometer. *Flow sensor. *Gas meter. *Mass flow sensor ... Arterial blood distributes oxygen throughout the body. Breath alcohol concentrations are generally lower than blood alcohol ... Breath analyzers do not directly measure blood alcohol content or concentration, which requires the analysis of a blood sample ... South Dakota had previously relied solely on blood tests to ensure accuracy, but has implemented evidential blood alcohol ...
An embolus proceeds through smaller and smaller arteries until it plugs one of them and prevents blood from flowing through the ... This dangerous situation is prevented by the AV node since its limited conduction velocity reduces the rate at which impulses ... High blood pressure[edit]. According to the CHARGE Consortium, both systolic and diastolic blood pressure are predictors of the ... sensitivity for locating thrombi in this area and can also detect sluggish blood flow in this area that is suggestive of blood ...
As such, the viscous stresses must depend on spatial gradients of the flow velocity. If the velocity gradients are small, then ... Blood 4 × 10−3 10−2 - 100 Oils and long-chain hydrocarbons Linseed oil 0.028 ... Just as heat flows from high temperature to low temperature and mass flows from high density to low density, momentum flows ... In many fluids, the flow velocity is observed to vary linearly from zero at the bottom to u. {\displaystyle u}. at the top. ...
Flow, fluid velocity. *Air flow meter. *Anemometer. *Flow sensor. *Gas meter. *Mass flow sensor ... Silicon pressure sensors e.g., car tire pressure sensors, and disposable blood pressure sensors ... embossing or stereolithography and are especially well suited to microfluidic applications such as disposable blood testing ...
Retrograde flow[edit]. Retrograde flow happens after the jet stream penetrates the skin and creates a hole, if the pressure of ... then tested the fluid remaining in the injector for blood. Every injector they tested had detectable blood in a quantity ... Splash-back refers to the jet stream penetrating the outer skin at a high velocity causing the jet stream to ricochet backwards ... Since the jet injector breaks the barrier of the skin, there is a risk of blood and biological material being transferred from ...
In particular there is a specialist study of blood flow called hemorheology. This is the study of flow properties of blood and ... The large class of fluids whose viscosity changes with the strain rate (the relative flow velocity) are called non-Newtonian ... Therefore, red blood cell mechanics is the major determinant of flow properties of blood.[14] ... Rheology (/riːˈɒlədʒi/; from Greek ῥέω rhéō, "flow" and -λoγία, -logia, "study of") is the study of the flow of matter, ...
2003). "Noninvasive measurement of regional cerebral blood flow and regional cerebral blood volume by near-infrared ... have also been developed for the detection of exoplanets using the Doppler shift of the parent star due to the radial velocity ... NIRS can be used to quantify blood flow, blood volume, oxygen consumption, reoxygenation rates and muscle recovery time in ... The use of NIRS in conjunction with a bolus injection of indocyanine green (ICG) has been used to measure cerebral blood flow[ ...
Blood flow and velocityEdit. The pulsatile nature of blood flow creates a pulse wave that is propagated down the arterial tree ... Another system divides the aorta with respect to its course and the direction of blood flow. In this system, the aorta starts ... The difference between aortic and right atrial pressure accounts for blood flow in the circulation.[16] When the left ventricle ... McDonald's Blood Flow in Arteries: Theoretical, Experimental and Clinical Principles. 4th ed. London, UK: Edward Arnold; 1998 ...
Velocity distribution Maxwellian: Collisions usually lead to a Maxwellian velocity distribution of all gas particles, with very ... Because fluid models usually describe the plasma in terms of a single flow at a certain temperature at each spatial location, ... in analogy with blood.[17][18] Mott-Smith recalls, in particular, that the transport of electrons from thermionic filaments ... is the velocity, and B. {\displaystyle \mathbf {B} }. is the magnetic field), and is not affected by Debye shielding.[37] ...
An Experimental Study of shock waves resulting from the impact of high velocity missiles on animal tissues[6][8]. ... Shi, H.; Kume, M. (2001). "An Experimental Research on the Flow Field of Water Entry by Pressure Measurements". Phys. Fluids. ... This is in contrast to factors such as proper shot placement and massive blood loss which are almost always eventually ... a b c YS Selman et al., Medico-legal Study of Shockwave Damage by High Velocity Missiles in Firearm Injuries, Fac Med Baghdad ...
Flow, fluid velocity. *Air flow meter. *Anemometer. *Flow sensor. *Gas meter. *Mass flow sensor ... allowing such applications as insertion into blood vessels via hypodermic needle. ... Extrinsic sensors measure vibration, rotation, displacement, velocity, acceleration, torque, and twisting. A solid state ...
A usual way of studying turbulent flow velocity fields is by means of flow velocity increments: δ. u. (. r. ). =. u. (. x. +. r ... which are due to turbulent blood flow. In normal individuals, heart sounds are a product of turbulent flow as heart valves ... Then one would find the actual flow velocity fluctuating about a mean value: v. x. =. v. x. ¯. ⏟. mean value. +. v. x. ′. ⏟. ... the flow velocity increment depends only on the modulus of r). Flow velocity increments are useful because they emphasize the ...
The blood flows from the dorsal aorta throughout the body. The deoxygenated blood from the body then flows through the ... greater than one and longitudinal velocity amplification; furthermore, this emergent velocity amplification may be augmented by ... The first part is the sinus venosus, a thin-walled sac that collects blood from the fish's veins before allowing it to flow to ... The bulbus arteriosus connects to the aorta, through which blood flows to the gills for oxygenation. In amphibians and most ...
Wexler, L.; D H Bergel; I T Gabe; G S Makin; C J Mills (1 September 1968). "Velocity of Blood Flow in Normal Human Venae Cavae ... "Flow velocity of single lymphatic capillaries in human skin". Am J Physiol Heart Circ Physiol. 270 (1): H358-H363. doi:10.1152/ ... If v = final velocity, u = initial velocity, a = acceleration, t = time, s = displacement, then : ... Motion is mathematically described in terms of displacement, distance, velocity, acceleration, time, and speed. Motion of a ...
The utility of using the bispectral index-Vista for detecting cross-clamping decline in cerebral blood flow velocity.. Dahaba ... a shunt consisted of a decline in transcranial Doppler ultrasonography-measured middle cerebral artery blood flow velocity ( ...
A study was carried out using Doppler ultrasound measurements of cerebral blood flow velocities (CBFV) as an indicator of ... Maintaining a constant cerebral blood flow during a change in cerebral perfusion pressure is known as autoregulation. The ... An informative response in CBFV was considered to be either (a) a uniphasic, immediate, passive alteration in velocity ...
1. Hyperemic Brachial Artery Blood Flow Velocity. Open this publication in new window or tab ,,Hyperemic Brachial Artery Blood ... Systolic blood flow velocity was positively related to cardiovascular risk whereas the diastolic velocity was inversely ... Brachial artery hyperemic blood flow velocities are related to carotid atherosclerosis. Järhult, Susann J. Uppsala University, ... Doppler recordings of blood flow velocity during hyperemia were analysed in the brachial artery. In the carotid artery, intima- ...
Intracoronary blood flow velocity reserve analysis is a sensitive technique for the detection of changes in blood flow. However ... CORONARY FLOW VELOCITY ANALYSIS. Coronary blood flow velocity measurements were performed with a Doppler angioplasty guide wire ... Blood flow velocities, using average peak velocity, were recorded at baseline and during hyperaemia. Hyperaemia was induced by ... Experimental data have shown that coronary flow velocity reserve (CFVR), the ratio of maximal to resting blood flow, is a ...
Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle.. K Ashikawa, H Kanatsuka ... Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle. ... Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle. ... Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle. ...
Doppler ultrasound was used to measure blood flow velocity in the anterior cerebral artery of six premature infants with ... There was a significant increase in mean blood flow velocity after the drainage procedures (+5.6 cm/s, 95% confidence interval ... Changes in cerebral artery blood flow velocity after intermittent cerebrospinal fluid drainage. ... Changes in cerebral artery blood flow velocity after intermittent cerebrospinal fluid drainage. ...
Increased middle cerebral artery mean blood flow velocity index after stroke thrombectomy indicates increased risk for ... Increased middle cerebral artery mean blood flow velocity index after stroke thrombectomy indicates increased risk for ...
Hemorrhage, Phenobarbital, and Fluctuating Cerebral Blood Flow Velocity in the Neonate. Karl C. K. Kuban, Helen Skouteli, Allen ... Hemorrhage, Phenobarbital, and Fluctuating Cerebral Blood Flow Velocity in the Neonate. Karl C. K. Kuban, Helen Skouteli, Allen ... Hemorrhage, Phenobarbital, and Fluctuating Cerebral Blood Flow Velocity in the Neonate Message Subject (Your Name) has sent you ...
V max = maximum blood flow velocity, V mean = mean of velocities across vessel lumen. See Fig. 3 for an angiogram of these two ... Blood flow velocity was studied in each common carotid artery. When the inspiratory gas was changed from 100% O 2 to 5% CO 2 in ... If one assumes an internal diameter of 4 mm, the calculated mean blood flow velocity within the vessel is 50 cm/sec. This ... as a function of mean blood flow velocity. Nature 227 : 926 - 930 , 1970 Begent N, Born GVR: Growth rate in vivo of platelet ...
The aim of this study is to characterize in resting-state conditions the cerebral blood flow velocity (CBFV) signals of ... Blood flow Is the Subject Area "Blood flow" applicable to this article? Yes. No. ...
... Rayra Pereira Santiago ... sickle erythrocytes decrease cerebral blood flow in rats after nitric oxide synthase inhibition," Blood, vol. 89, no. 12, pp. ... R. L. Nagel, M. E. Fabry, and M. H. Steinberg, "The paradox of hemoglobin SC disease," Blood Reviews, vol. 17, no. 3, pp. 167- ... C. Vieira, C. N. Oliveira, L. A. Figueiredo et al., "Transcranial Doppler in hemoglobin SC disease," Pediatric Blood & Cancer, ...
... and blood-brain barrier permeability, thus affecting regional metabolism and blood flow regulation (4). Xenon blood flow (5) ... The aim of this study was to assess the effects of type 2 diabetes on blood flow velocities (BFVs) in the middle cerebral ... Cerebral Blood Flow Velocity and Periventricular White Matter Hyperintensities in Type 2 Diabetes. ... Cerebral Blood Flow Velocity and Periventricular White Matter Hyperintensities in Type 2 Diabetes ...
Lactic dehydrogenase (LDH) independently predicted cognitive function, but blood flow velocity did not mediate this ... and these relationships do not appear to be mediated through blood flow velocity. Although the lack of association among ... there were few significant independent associations between biomarkers or blood flow velocity and estimated IQ. ... as well as transcranial Doppler velocities, hydroxyurea use, and demographic information were obtained. ,i,Results,/i,. Using ...
... velocity mapping to calculate pulmonary-to-systemic flow ratio (Qp : Qs) in patients with a suspected... ... Quantification of pulmonary and systemic blood flow by magnetic resonance velocity mapping in the assessment of atrial-level ... MR velocity mapping offers an accurate method to measure aortic and pulmonary artery volume flow that can be useful in the ... atrial septal defect intracardiac shunt blood flow magnetic resonance imaging This is a preview of subscription content, log in ...
The blood flow velocity can be used as boundary condition for exact blood flow simulations that can help physicians to ... We propose a system to estimate blood flow velocity in angiographic image data for patient-specific blood flow simulations. ... Estimating blood flow velocity in angiographic image data Author(s): Clemens M. Hentschke; Steffen Serowy; Gábor Janiga; Georg ... Projective blood flow is measured in digital subtraction X-ray angiography (2D-DSA) images by tracking contrast agent ...
Results: Resting baseline values: overall maximum blood flow velocity 26.49 cm/s (SD: 9.99 cm/s), mean blood flow velocity 8.46 ... Results: Resting baseline values: overall maximum blood flow velocity 26.49 cm/s (SD: 9.99 cm/s), mean blood flow velocity 8.46 ... Mean percentage increase of maximum blood flow velocity is 36.5%, mean blood flow velocity 243%. PI was reduced by 52.8%. There ... Mean percentage increase of maximum blood flow velocity is 36.5%, mean blood flow velocity 243%. PI was reduced by 52.8%. There ...
Diehl RR, Linden D, Lucke D, Berlit P. Phase relationship between cerebral blood flow velocity and blood pressure: a clinical ... The change in flow velocity relative to the change in pressure was determined by dividing individual changes in flow velocity ... Dynamic Regulation of Middle Cerebral Artery Blood Flow Velocity in Aging and Hypertension. Lewis A. Lipsitz, Seiji Mukai, ... Continuous BP (top panels) and MCA blood flow velocity (bottom panels) waveforms during 15 seconds of sitting and 25 seconds of ...
... a selective A2A adenosine receptor agonist and vasodilator used to increase the heterogeneity of distribution of coronary blood ... flow during myocardial perfusion imaging. This study characterized the dose dependence of regad ... central aortic blood pressure, and adverse effects were recorded. Regadenoson increased peak blood flow velocity by up to 3.4- ... Blood Flow Velocity / drug effects*. Coronary Circulation / drug effects*. Dose-Response Relationship, Drug. Female. Humans. ...
Recent advances in blood flow vector velocity imaging. Publication: Research - peer-review › Article in proceedings - Annual ... Several vector velocity image sequences of complex flow were acquired, which demonstrates the benefits of fast vector flow ... Aortic Valve Stenosis Increases Helical Flow and Flow Complexity: A Study of Intra-operative Cardiac Vector Flow Imaging. ... Accuracy and Precision of Plane Wave Vector Flow Imaging for Laminar and Complex Flow In Vivo. Publication: Research - peer- ...
Blood flow velocity in the uterine and ovarian arteries during the normal menstrual cycle. Sladkevicius, Povilas LU ; Valentin ... Doppler ultrasound, blood flow velocity, menstrual cycle. in Ultrasound in Obstetrics & Gynecology. volume. 3. issue. 3. pages ... blood flow velocity,menstrual cycle}, language = {eng}, number = {3}, pages = {199--208}, publisher = {John Wiley & Sons}, ... series = {Ultrasound in Obstetrics & Gynecology}, title = {Blood flow velocity in the uterine and ovarian arteries during the ...
Blood flow velocity in the middle cerebral artery (MCAv) may be used as a proxy measure of cerebral blood flow. Using ... Effect of magnesium, high altitude and acute mountain sickness on blood flow velocity in the middle cerebral artery Christopher ... high altitude and acute mountain sickness on blood flow velocity in the middle cerebral artery. Clin Sci (Lond) 1 March 2004; ... Cerebral blood flow is thought to increase at high altitude and in subjects suffering from acute mountain sickness (AMS); ...
Ultrasound Measurement of Vertebral Artery Blood Flow Before and After High-Velocity, Low-Amplitude Thrust Therapy. The Journal ... The immediate effect of atlanto-axial high velocity thrust techniques on blood flow in the vertebral artery: a randomized ... Ultrasound Measurement of Vertebral Artery Blood Flow Before and After High-Velocity, Low-Amplitude Thrust Therapy. J Am ... Ultrasound Measurement of Vertebral Artery Blood Flow Before and After High-Velocity, Low-Amplitude Thrust Therapy ...
... with the basic approximations of the axisymmetric flow in cylindri ... An empirical parametric equation with 2 bluntness parameters was introduced for describing the velocity profile of blood in the ... A velocity profile equation for blood flow in small arterioles and venules of small mammals in vivo and an evaluation based on ... An empirical parametric equation with 2 bluntness parameters was introduced for describing the velocity profile of blood in the ...
... of von Willebrand Factor to Thrombus Formation on Neointima of Rabbit Stenotic Iliac Artery Under High Blood-Flow Velocity. ... of von Willebrand Factor to Thrombus Formation on Neointima of Rabbit Stenotic Iliac Artery Under High Blood-Flow Velocity ... of von Willebrand Factor to Thrombus Formation on Neointima of Rabbit Stenotic Iliac Artery Under High Blood-Flow Velocity ... of von Willebrand Factor to Thrombus Formation on Neointima of Rabbit Stenotic Iliac Artery Under High Blood-Flow Velocity ...
Diehl RR, Linden D, Lücke D, Berlit P. Phase relationship between cerebral blood flow velocity and blood pressure. A clinical ... leading to a prolonged and widely distributed increased blood flow demand. In such a condition, an increase of blood flow ... The Linear Behavior of the System Middle Cerebral Artery Flow Velocity and Blood Pressure in Patients With Migraine. Lack of ... There were no differences between patients with and without aura regarding mean BP, mean values of blood flow velocities, and ...
Z.-H. Ma, Y.-S. Ma, Y.-Q. Zhao, J. Liu, J.-H. Liu, J.-T. Lv, and Y. Wang, "Measurement of the absolute velocity of blood flow ... Measurement of absolute blood flow velocity in outflow tract of HH18 chicken embryo based on 4D reconstruction using spectral ... and absolute blood flow was determined. We validate this method in a capillary tube as well as in large blood vessels of early- ... Measurement of the absolute velocity of blood flow in early-stage chick embryos using spectral domain optical coherence ...
Blood flow velocity in the middle cerebral artery (MCAv) may be used as a proxy measure of cerebral blood flow. Using ... Effect of magnesium, high altitude and acute mountain sickness on blood flow velocity in the middle cerebral artery. ... Effect of magnesium, high altitude and acute mountain sickness on blood flow velocity in the middle cerebral artery ... Effect of magnesium, high altitude and acute mountain sickness on blood flow velocity in the middle cerebral artery ...
Increased Velocity of Retinal Blood Flow in RP subjects with Significantly Improved Visual Function following Transcorneal ... Increased Velocity of Retinal Blood Flow in RP subjects with Significantly Improved Visual Function following Transcorneal ... Ava Katherine Bittner, Kenneth R Seger, Samantha Kayser, J C Ramella-Roman; Increased Velocity of Retinal Blood Flow in RP ... Purpose : To examine the repeatability of and changes in retinal blood velocity (RBV) in the macular capillaries of retinitis ...
The results suggest a relation between nailfold capillary blood cell velocity and blood flow velocity in the ophthalmic artery ... The relatively constant blood flow during the diastole might predict more closely blood cell velocity in the capillary bed. ... However, RI is not a measure of velocity. PSV represents a unique event in arterial blood flow, and, possibly, capillary blood ... 4 The velocities measured in each visible vessel were averaged. Blood flow velocity in the ophthalmic arteries was assessed by ...
4D-flow MRI can provide comprehensive hemodynamics with accurate blood flow and velocity.2 MMD-derived concentrated inflow jet ... demonstrates blood flow direction (arrow). Velocity diagram (E, F) demonstrates maximum velocity variation throughout cardiac ... Teaching Video NeuroImages: High blood flow velocity in the parent artery prior to basilar tip aneurysm rupture. Fei Peng, ... Teaching Video NeuroImages: High blood flow velocity in the parent artery prior to basilar tip aneurysm rupture ...
  • 6 The development of a Doppler tipped angioplasty guide wire has made it possible to measure flow velocity distal to a coronary lesion in the clinical setting. (bmj.com)
  • Attempts to measure left ventricular stroke volume utilizing the Doppler aortic flow method have found varying correlations between invasive thermodilution and non-invasive Doppler methods. (escholarship.org)
  • Because stroke volume is the product of the Doppler flow velocity integral (that is, the area under the flow velocity curve) and the cross-sectional area of the vessel through which blood flows, both variables are potential sources of error. (escholarship.org)
  • Previous studies have shown that the Doppler flow velocity integral can be measured with acceptable reproducibility in the ascending aorta. (escholarship.org)
  • Doppler aortic flow velocity patterns were recorded with a 2.25 MHz M-mode echocardiographic transducer from the suprasternal notch by mapping the ascending aorta until aortic peak flow velocity was recorded. (escholarship.org)
  • For example, doctors usually determine whether the heart is pumping enough blood through the primary arteries to end organs by taking an ultrasound measurement called Velocity Time Integral (VTI). (ge.com)
  • Intracoronary blood flow velocity analysis could obviate the need for additional myocardial perfusion scintigraphy in the majority of patients. (bmj.com)
  • A cytokine "storm" dilates blood vessels, making them leaky. (ge.com)
  • 12-14 The relative CFVR (rCFVR), the ratio of poststenotic coronary flow velocity to the coronary flow velocity in a normal reference vessel, is compared to the absolute coronary flow velocity relatively independent of these variables. (bmj.com)
  • Experimental data have shown that coronary flow velocity reserve (CFVR), the ratio of maximal to resting blood flow, is a sensitive and reliable index of the functional severity of a coronary stenosis. (bmj.com)
  • Previous in vivo investigations of aortic helicity were based on the qualitative evaluation of helical flow using 2D vector arrow plots or 3D streamlines and 3D pathlines, which provide a visual impression of the magnitude and sense of rotation [6, 10-12]. (uniklinik-freiburg.de)
  • 3D flow characteristics in a healthy volunteer (a) and a patient with aortic valve disease (b). (uniklinik-freiburg.de)
  • 3D blood flow characteristics within the aorta are complex and dependent on the individual geometry and shape of the aorta. (uniklinik-freiburg.de)
  • A 4D flow dataset contains a huge amount of information which needs to be carefully processed in order to extract the useful information. (uniklinik-freiburg.de)
  • Sieverding L, Jung W-I, Klose U, Apirz J. Noninvasive blood flow measurement and quantification of shunt volume by cine magnetic resonance in congenital heart disease. (springer.com)
  • The purpose was to evaluate the usefulness of this equation in describing the velocity profile and in estimating the volume flow when only one velocity measurement is available near the vessel axis. (biomedsearch.com)
  • Z.-H. Ma, Y.-S. Ma, Y.-Q. Zhao, J. Liu, J.-H. Liu, J.-T. Lv, and Y. Wang, "Measurement of the absolute velocity of blood flow in early-stage chick embryos using spectral domain optical coherence tomography," Appl. (osapublishing.org)
  • 8 Although the measurement of EDV is less reproducible compared with PSV and RI, 7 a fact which is expected to alter a potential correlation, nailfold capillary blood cell velocity correlated with EDV and MV in the ophthalmic artery. (bmj.com)
  • Cerebral atherosclerotic changes in the left carotid artery were measured noninvasively with an ultrasonic quantitative flow measurement system (QFM 2000XA,Hihon Koden Co., Ltd, Tokyo). (nii.ac.jp)
  • The objectives of this prospective cross sectional study are (i) to establish new reference values of peak systolic blood flow velocity measurement in the fetal middle cerebral artery (MCA-PSV) following validated methodological guidelines (ii) to correlate peak systolic velocity with gestational age and (iii) to establish regression prediction model of MCA-PSV for our population. (ajol.info)
  • A 22-gauge catheter was inserted into the radial artery to measure mean arterial pressure (MAP) continuously and to draw blood samples for measurement of Pa CO 2 . (asahq.org)
  • However, the measurement of total absolute blood flow velocity (BFV) of major cerebral arteries is still a difficult problem since it is related to vessel geometry. (escholarship.org)
  • Zhangyi Zhong, Benno L. Petrig, Xiaofeng Qi, and Stephen A. Burns, "In vivo measurement of erythrocyte velocity and retinal blood flow using adaptive optics scanning laser ophthalmoscopy," Opt. (osapublishing.org)
  • Relying upon these two models, we construct a discrete Kalman filter for the recursive estimation of the blood velocity envelope, while taking into account the measurement noise from these two sources. (city.ac.uk)
  • The device is designed to reduce the time of measurement of blood flow. (russianpatents.com)
  • A device for measuring the velocity of capillary blood flow (Uly-anov S. S., Tuchin V. V. Partially developed speckle-field dynamics for blood microcirculation and biovibration parameters measurement. (russianpatents.com)
  • The purpose of this study was to measure blood flow velocities in carotid, brachial and femoral arteries simultaneously during passive postural change using our developed telemetry measurement system. (iium.edu.my)
  • This study demonstrated that synchronized measurement of blood flow velocity waveforms in carotid, brachial, and femoral in HUT postural change using our telemetry measurement device was attainable. (iium.edu.my)
  • Conventional one-directional (1-dir) velocity-encoded (VE) MRI is routinely used for flow assessment over the mitral (MV) and tricuspid valve (TV), but this technique has been shown to be inaccurate and correlation between 1-dir VE MRI MV- and TV-flow measurement is weak. (biomedcentral.com)
  • Results: Resting baseline values: overall maximum blood flow velocity 26.49 cm/s (SD: 9.99 cm/s), mean blood flow velocity 8.46 cm/s (SD: 6.17 cm/s), and pulsatility index (PI) 5.46 (SD: 5.7) for the whole group. (muni.cz)
  • The pulsatility index and the time-averaged maximum velocity were calculated. (lu.se)
  • In the uterine arteries the pulsatility index was highest on day + 2, after which it decreased successively to its lowest value, whereas the time-averaged maximum velocity reached its. (lu.se)
  • In the non-dominant ovary, neither the pulsatility index nor the time-averaged maximum velocity manifested any consistent changes during the cycle. (lu.se)
  • In the dominant ovary, the time-averaged maximum velocity increased and the pulsatility index decreased after follicular rupture, being significantly higher and lower, respectively, in the luteal than in the follicular phase. (lu.se)
  • An automated, closed-loop 1D-0D modelling framework was developed, and we demonstrate its efficacy in (1) reproducing measured multi-variate cardiovascular variables (pulse pressure, total peripheral resistance and cardiac output) and (2) providing automated estimates of variables that have not been measured (uterine arterial and venous blood flow, pulse wave velocity, pulsatility index). (springer.com)
  • Mean and peak velocity and pulsatility index of the ipsilateral middle cerebral artery (MCA) were measured by TCD. (elsevier.com)
  • The aim of this study was to assess the effects of type 2 diabetes on blood flow velocities (BFVs) in the middle cerebral arteries and to determine the relationship between white matter hyperintensities (WMHs) on magnetic resonance imaging (MRI) and BFVs. (diabetesjournals.org)
  • Aim: Our aim was to automatically estimate the blood velocity in coronary arteries using cine X-ray angiographic sequence. (uib.no)
  • Central alpha 2 receptors have a role in the regulation of the cerebral circulation, [2] and alpha 2 agonists, including clonidine, decrease cerebral blood flow (CBF), [3-6] and produce constriction of cerebral arteries. (asahq.org)
  • In the presence of severe coronary artery stenosis, it is not clear whether intraaortic balloon pumping augments intramyocardial inflow during diastole or changes systolic retrograde blood flow from the myocardium to the extramural coronary arteries. (onlinejacc.org)
  • Peak systolic, end diastolic and mean velocities of nine main intracranial arteries were determined using TCD. (biomedcentral.com)
  • Mean blood flow velocity in middle, anterior and posterior cerebral arteries, vertebral and basilar arteries was 60 ± 8, 52 ± 9, 42 ± 6, 39 ± 8 and 48 ± 8 cm/sec respectively. (biomedcentral.com)
  • Consider that the aorta branches into the other arteries, and these in turn branch into the arterioles, and so forth until blood finally flows into the capillaries. (lubopitko-bg.com)
  • Dynamics of blood flow velocity changes in cerebral arteries in acute phase of stroke depends on the pattern of blood flow at the beginning of stroke and occurs mainly in patients with large artery lesion. (viamedica.pl)
  • The speed of travel of this pulse wave (pulse wave velocity (PWV)) is related to the stiffness of the arteries. (wikipedia.org)
  • This function depends on the elasticity of the arteries and stiffened arteries require a greater amount of force to permit them to accommodate the volume of blood ejected from the heart (stroke volume). (wikipedia.org)
  • Pulse wave velocity (PWV) is the velocity at which the blood pressure pulse propagates through the circulatory system , usually an artery or a combined length of arteries. (wikipedia.org)
  • This is the first model capable of estimating volumetric blood flow to the uterus via the utero-ovarian communicating arteries. (springer.com)
  • A better analogy is speed of sound waves in fluid, where, as in arteries, velocity depends on physical properties of the medium over which the wave travels. (ahajournals.org)
  • McDonald's Blood Flow in Arteries: Theoretical, Experimental and Clinical Principles. (ahajournals.org)
  • The purpose of this study is to determine if external counterpulsation (ECP) is feasible to perform, tolerable, and safe as a treatment for patients with acute ischemic stroke (i.e., a blockage of one of the arteries supplying a part of the brain), and to assess what type of effect it might have on 1) the velocity of blood flow in the arteries supplying the brain and 2) stroke symptoms. (clinicaltrials.gov)
  • Poor circulation in the lower extremities occurs when plaque builds up in the arteries that supply blood to the legs. (buzzle.com)
  • Peak systolic SI and end-diastolic d velocities were obtained from the velocity waveforms in 3 arteries, and using these velocities as an index of d/Sl to assess the velocity waveforms during the postural change. (iium.edu.my)
  • The velocity waveforms of 3 arteries, heart rate (HR), and blood pressure (BP) were assessed for 20 s at the stages of postural change. (iium.edu.my)
  • In this report the authors describe a noninvasive transcranial method of determining the flow velocities in the basal cerebral arteries. (thejns.org)
  • The flow velocities in the proximal anterior (ACA) and posterior (PCA) cerebral arteries were also recorded at steady state and during test compression of the common carotid arteries. (thejns.org)
  • To investigate the association between diameter and flow velocity of the carotid arteries and ischemic stroke. (elsevier.com)
  • Antegrade and retrograde flow were measured in the ascending aorta, in the right and left common, internal, and external carotid arteries, and in the vertebral arteries of 12 healthy subjects. (elsevier.com)
  • Mean blood flow velocity was measured in both right and left middle cerebral arteries (MCA) at rest and during a word generation task, and changes in flow velocities were compared. (ac.ir)
  • 10 The instrument was initially designed for determining instantaneous arterial or venous blood flow velocity through the intact skin 14 and is dependent on the frequency shift of ultrasonic waves reflected from moving red blood cells. (thejns.org)
  • Comparison of phasic blood flow velocity characteristics of arterial and venous coronary artery bypass conduits. (semanticscholar.org)
  • Atherothrombotic occlusion of venous conduits has previously been correlated with lower flow rates measured intraoperatively. (semanticscholar.org)
  • However, stroke volume and heart rate increase blood pressure only if the venous return is adequate. (lubopitko-bg.com)
  • This aids the flow of venous blood back to the heart because blood flows in the direction of reduced pressure. (lubopitko-bg.com)
  • As you might suspect, gravity can assist the return of venous blood from the head to the heart but not the return of blood from the extremities and trunk to the heart. (lubopitko-bg.com)
  • Designed to ensure blood flow viscosity and reduce venous stasis below the knee when thigh-length styles are medically contraindicated, TED anti embolism stockings are available in a number of different options to suit your specific needs. (mvsdiscountsales.com)
  • In contrast, the blood flow in the brachial and femoral was more influenced of venous pressure (VP) in postural change. (iium.edu.my)
  • 2: the crucial role of the predural venous section in conditioning the cerebral blood flow. (elsevier.com)
  • MR velocity mapping offers an accurate method to measure aortic and pulmonary artery volume flow that can be useful in the evaluation of atrial-level shunts, in order to establish a definite diagnosis and/or to quantify the Qp : Qs ratio. (springer.com)
  • Left anterior descending arterial flow, aortic pressure and poststenotic distal coronary pressure were measured simultaneously. (onlinejacc.org)
  • Aortic regurgitation is associated with retrograde diastolic flow in the aorta. (nih.gov)
  • The purpose of this study was to evaluate the uniformity of flow patterns in the aorta of patients with aortic regurgitation and to investigate the relationship between these profiles and the echocardiographic estimates of flow reversal. (nih.gov)
  • The regurgitant fraction in the ascending aorta 4 cm above the aortic valve and the descending aorta were calculated from the velocity maps. (nih.gov)
  • Responses of cerebral blood flow to the postural unloading maneuver in aortic stenosis (AS) have not been described so far. (viamedica.pl)
  • Some of the methods used to study the hemodynamics of aortic flow are patient scans, computational fluid dynamics models, and particle tracking velocimetry (PTV). (wikipedia.org)
  • As the blood moves into the aortic arch, the area with the highest velocity tends to be on the inner wall. (wikipedia.org)
  • Helical flow within the ascending aorta and aortic arch help to reduce flow stagnation and increase oxygen transport. (wikipedia.org)
  • As age increases the aortic diameter tends to increase and the peak velocity of systolic flow tends to decrease until patients reach an age greater than 60 years old. (wikipedia.org)
  • The presence of diabetes affects the dynamic viscosity of blood and the compliance of the aortic walls. (wikipedia.org)
  • Westerhof BE, van den Wijngaard JP, Murgo JP, Westerhof N. Location of a reflection site is elusive: consequences for the calculation of aortic pulse wave velocity. (ahajournals.org)
  • Systolic aortic flow measured with 1-dir VE MRI was used as the standard of reference. (biomedcentral.com)
  • In volunteers, a significant bias was found for 1-dir VE MRI for both MV (over-estimation 11 ml/cycle) and TV (over-estimation 12 ml/cycle) compared to the aortic flow volume, while 3D VE MRI showed no bias and small confidence intervals. (biomedcentral.com)
  • Correlation with aortic flow volume was strong for 3D VE MRI (r = 0.96 for MV, r = 0.88 for TV) and strong between MV and TV (r = 0.91). (biomedcentral.com)
  • Correlation with aortic flow volume was weak for 1-dir VE MRI (r = 0.80 for MV, r = 0.22 for TV) and weak between MV and TV (r = 0.34). (biomedcentral.com)
  • Although correlation for MV- and TV-flow with aortic flow was also good, these showed significant bias due to the aortic valve regurgitation that was present in several cases. (biomedcentral.com)
  • The purpose of this study was to evaluate the correlation between the retinal blood flow assessed by the retinal functional imager (RFI) and central macular thickness/volume assessed by the scanning laser ophthalmoscopy-optical coherence tomography (SLO-OCT) system. (arvojournals.org)
  • The retinal capillary maps produced by RFI are similar to the en face view of the retinal capillary maps created by optical coherence tomography angiography (OCTA). (biomedcentral.com)
  • 12 found an average mean flow of 370 ml/min in the human internal carotid artery. (thejns.org)
  • Eight patients with aneurysms at the para-ophthalmic segment of the internal carotid artery were treated by flow diversion only. (epfl.ch)
  • Purpose: To establish reference values of the ratios of flow velocity in the middle cerebral artery (V MC A) and the terminal portion of the internal carotid artery (V tICA ) to flow velocity in the extracranial portion of internal carotid artery (V ICA ) in children with sickle cell disease (SCD). (elsevier.com)
  • Maximal and mean transaortic pressure gradients, as well as peak systolic blood-flow velocity (PSV) and end-diastolic velocity (EDV) in the common carotid artery, internal carotid artery and vertebral artery on both sides were measured by duplex ultrasound in the supine position and at 1-2 min after the assumption of the sitting position in patients with AS, and in stand-ing position in healthy controls. (viamedica.pl)
  • Acute as well as chronic stable IS patients had significantly lower flow velocities and flow volume, higher resistance index than nonstroke controls in the common carotid artery (CCA), internal carotid artery and external carotid artery, and larger common carotid artery diameter. (elsevier.com)
  • All right-handed subjects had higher flow rates in the left internal carotid artery than in the right, and all left-handed subjects had higher flow rates in the right internal carotid artery (P = .007). (elsevier.com)
  • The immediate effect of atlanto-axial high velocity thrust techniques on blood flow in the vertebral artery: a randomized controlled trial [published online March 2, 2015]. (jaoa.org)
  • This description of the intervention is similar to high-velocity, low-amplitude procedures. (jaoa.org)
  • A 70-year-old asymptomatic man presented with moyamoya disease (MMD)-associated basilar tip aneurysm (BTA) noted on digital subtraction angiography ( figure 1, A-D ). 4D-flow MRI revealed a concentrated inflow jet with high velocity compared with previous studies 1 ( video 1 and figure 2, A-F ). Considering the high risk of endovascular treatment, the patient chose conservative treatment. (neurology.org)
  • Thus, high-velocity blood flow rapidly pushed the PFO open, which resulted in a significant increase in the PFO-RLS. (scirp.org)
  • Therefore, the increase of the PFO-RLS during the Valsalva maneuver is caused by the impact of high-velocity blood flow the PFO. (scirp.org)
  • Physiological abnormalities due to plague formation or aneurysm lead to helical flows and high velocity flows in locations where they would not normally be present or as prominent. (wikipedia.org)
  • The abnormal high velocity areas generate a higher amount of wall shear stress than normal and contribute to stenosis and further plaque formation. (wikipedia.org)
  • However, the correlation between increased blood velocity as measured by TCD ultrasonography and angiographic vasospasm was established before the routine use of hypervolemia/hemodilution and administration of nimodipine and did not address blood flow. (semanticscholar.org)
  • Final study population comprised 56 (mean age 8.0 ± 3.3 years, 26 females) children who underwent magnetic resonance (MR) angiography, which excluded intracranial arterial narrowing, transcranial color-coded duplex ultrasonography (US), and carotid US to determine V MCA /V ICA and V tICA /V ICA ratios from angle-corrected and uncorrected velocities. (elsevier.com)
  • Ascending aorta and main pulmonary artery volume flow were measured with MR velocity mapping. (springer.com)
  • The cross-sectional area of the two venae cavae is more than twice that of the aorta, and the velocity of the blood returning to the heart remains low compared to the blood leaving the heart. (lubopitko-bg.com)
  • You would expect blood pressure to be highest in the aorta. (lubopitko-bg.com)
  • Because the pumping action of the heart forces blood into the aorta. (lubopitko-bg.com)
  • A new method of presenting magnetic resonance phase information is described and an example of its application given in the context of velocity phase-encoded MRI of blood flow in the aorta. (elsevier.com)
  • Dymond, RC , Redpath, TW & McKiddie, FI 1996, ' Application of the principle of optical phase-contrast microscopy to velocity phase-encoded MRI of blood flow in the aorta ', British Journal of Radiology , vol. 69, no. 821, pp. 410-414. (elsevier.com)
  • The hemodynamics of the aorta is an ongoing field of research in which the goal is to identify what flow patterns and subsequent forces occur within the thoracic aorta. (wikipedia.org)
  • The mean velocity in the aorta varies over the cardiac cycle. (wikipedia.org)
  • As the path starts to curve in the ascending aorta, the blood towards the outside of the arch tends to rotate towards the inner wall, causing a helical pattern that is observed in most individuals. (wikipedia.org)
  • As the blood moves into the descending aorta, rotations in the flow are less present. (wikipedia.org)
  • Simulations of these flow patterns seek to identify what normal wall shear stress conditions and helical flows are present at specific location within the aorta. (wikipedia.org)
  • It is also observed that the outlet velocity of the descending aorta is lower in the diabetes model. (wikipedia.org)
  • The blood pressure in the diabetes model is lower than that of the control model, but the mean pressures of the entire aorta are similar between both models. (wikipedia.org)
  • CFD models allow for researchers to recreate flows happening within the aorta and evaluate factors that cannot be obtained through normal patient scans. (wikipedia.org)
  • The aorta distributes oxygenated blood to all parts of the body through the systemic circulation . (wikipedia.org)
  • Another system divides the aorta with respect to its course and the direction of blood flow. (wikipedia.org)
  • 1 Because these and newer observations 3 suggest some parallels in ocular and digital blood flow regulation, the relation between ophthalmic artery and nailfold capillary blood flow velocities was evaluated. (bmj.com)
  • PSV represents a unique event in arterial blood flow, and, possibly, capillary blood flow fluctuations may not be related directly to very brief moments during the cardiac cycle. (bmj.com)
  • Experimental data have shown that coronary flow velocity reserve (CFVR), the ratio of maximal to resting blood flow, is a sensitive and reliable index of the functional severity of a coronary stenosis. (bmj.com)
  • We conclude that spiral phase velocity mapping has the potential to assess temporal patterns of coronary flow velocity non-invasively. (ismrm.org)
  • Fingerprint Dive into the research topics of 'Carotid and vertebral artery blood flow in left- and right-handed healthy subjects measured with MR velocity mapping. (elsevier.com)
  • This technique is a rapid and effective method for the noninvasive assessment of blood flow velocity in IMA grafts. (elsevier.com)
  • To determine the inter-visit variability of retinal blood flow velocities (BFVs) using a retinal function imager (RFI) in healthy young subjects. (biomedcentral.com)
  • The impact of ligation of proximal side branches on blood flow and functional status of the internal thoracic artery in coronary anastomosis. (semanticscholar.org)
  • C) gene polymorphisms with cerebrovascular disease in a newborn cohort of 411 children with sickle cell anemia," Blood Cells, Molecules & Diseases , vol. 54, no. 1, pp. 44-50, 2015. (hindawi.com)
  • Clonidine has been reported to decrease cerebral blood flow and reduce cerebral CO 2 vasoreactivity [2] and to enhance cerebrovascular reactivity to CO 2 . (asahq.org)
  • Inclusion criteria included normal middle cerebral artery (MCA) blood flow velocities, as determined by TCD evaluation, and a negative history for cardiac or cerebrovascular disease. (asahq.org)
  • Cerebral vasoregulation is a complex mechanism concerning the ability of the cerebrovascular system to maintain within certain limits a constant blood flow against physiologic or pathologic variations of the perfusion pressure and/or systemic metabolism. (elsevier.com)
  • Analysis of the blood flow velocity in the forearm was made in comparison to established methods of estimating endothelial function, clinical markers of cardiovascular risk, the Framingham risk score and global atherosclerosis determined by whole body magnetic resonance angiography. (diva-portal.org)
  • The relationship between arterial stiffness and pulse wave velocity was first predicted by Thomas Young in his Croonian Lecture of 1808 but is generally described by the Moens-Korteweg equation or the Bramwell-Hill equation. (wikipedia.org)
  • Devices are on the market that measure arterial stiffness parameters (augmentation index, pulse wave velocity). (wikipedia.org)
  • The theory of the velocity of the transmission of the pulse through the circulation dates back to 1808 with the work of Thomas Young . (wikipedia.org)
  • Taylor 3,4 and McDonald 2 considered that pulse wave velocity (PWV) of a forward-traveling wave is identical to PWV of the reflected wave, and both are directly related to the properties of the arterial wall. (ahajournals.org)
  • Blood flow velocity in retinal veins, analyzed by RFI, significantly correlates with the volume of central retina. (arvojournals.org)
  • NOS inhibition significantly attenuated the increase in leg glucose uptake during exercise by ∼40% at 15 min of exercise compared with the saline infusion without influencing leg blood flow or arterial glucose and insulin concentrations ( 4 ). (diabetesjournals.org)
  • The right and left inferior thyroid artery -peak systolic and end-diastolic velocities in patients with gestational transient thyrotoxicosis were found to be significantly lower than those of pregnant patients with Graves' disease and higher than those of healthy euthyroid subjects. (bvsalud.org)
  • However, the right and left inferior thyroid artery peak systolic and end-diastolic velocities in pregnant patients with Graves' disease were significantly lower than those of non-pregnant patients with Graves' disease . (bvsalud.org)
  • Systolic blood flow velocity was positively related to cardiovascular risk whereas the diastolic velocity was inversely correlated. (diva-portal.org)
  • However, the systolic to diastolic blood flow velocity (SDFV) ratio was more closely associated with cardiovascular risk than its components apart. (diva-portal.org)
  • In conclusion, during reactive hyperemia of the Brachial artery, the systolic to diastolic blood flow velocity ratio appears to contain information of additional value than its components separately, independently of established cardiovascular risk factors. (diva-portal.org)
  • 3. total blood volume in the cardiovascular system. (lubopitko-bg.com)
  • Let's check the pathway of blood through the heart and its functions in the cardiovascular system. (buzzle.com)
  • Sequence optimization to reduce velocity offsets in cardiovascular magnetic resonance volume flow quantification--a multi-vendor study. (mendeley.com)
  • One aneurysm rupturing 5 days after treatment showed also no change in flow pattern, and no change in the maximal inflow velocity. (epfl.ch)
  • Magnetic resonance velocity mapping was used to investigate the hypothesis of a vortex motion within the left ventricle interacting with mitral valve motion and inflow velocity. (onlinejacc.org)
  • PURPOSE: To compare cerebral blood flow velocities between open-angle glaucoma (OAG) patients and controls, at baseline and during hyperoxia. (elsevier.com)
  • Aminophylline (100 mg) attenuated the increase in peak flow velocity but not tachycardia caused by 400 microg of regadenoson. (biomedsearch.com)
  • [ 36 ] Postmenopausal-aged women not on hormone replacement therapy have worse physiologic sexual response, including a lower increase in genital blood peak flow velocity. (medscape.com)
  • Breath-hold VENC-MR imaging demonstrated higher peak flow velocity in the IMA than nonbreath-hold VENC-MR imaging. (elsevier.com)
  • The aim of this study was to quantitatively evaluate changes in choroidal blood flow velocity by using laser speckle flowgraphy (LSFG) in patients with PIC. (biomedcentral.com)
  • Macular choroidal blood flow velocity increased and choroidal thickness decreased concurrently with regression of PIC. (biomedcentral.com)
  • In the present study, we quantitatively measured choroidal blood flow velocity at the macula using LSFG in a PIC patient treated with systemic corticosteroids. (biomedcentral.com)
  • Circulatory shock symptoms are generally associated with complications in blood supply to organs and cells as a result of which a person might suffer from abnormally low/high blood pressure and even cardiac arrest. (buzzle.com)
  • Blood flow velocity was studied in each common carotid artery. (thejns.org)
  • There were no significant differences in left and right common carotid artery flow rates between left- and right-handed subjects. (elsevier.com)
  • G6PD deficiency, absence of alpha-thalassemia, and hemolytic rate at baseline are significant independent risk factors for abnormally high cerebral velocities in patients with sickle cell anemia," Blood , vol. 112, no. 10, pp. 4314-4317, 2008. (hindawi.com)
  • Since the publication of the Stroke Prevention Trial in Sickle Cell Anemia in 1998 and introduction of TCD screening, prophylactic blood transfusions, and hydroxyurea, the incidence of stroke has decreased. (hindawi.com)