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 ...
How is Mitral Flow Velocity Pattern abbreviated? MFVP stands for Mitral Flow Velocity Pattern. MFVP is defined as Mitral Flow Velocity Pattern very rarely.
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 +/- ...
also applies to total volume). Gross Flow = volumetric flow rate at actual conditions (observed) - what most flow instruments measure. Net Flow = volumetric flow rate converted to flow rate at standard conditions - usually 60 deg F. WHY NET? To keep consistent - measure flow at -20 deg F, then product heats up to 40 deg F - different observed amount of product. You wouldnt want to keep changing the amounts used in records, procedures, designs, sales, etc.. ...
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 ...
Powered by Pure, Scopus & Elsevier Fingerprint Engine™ © 2021 Elsevier B.V. We use cookies to help provide and enhance our service and tailor content. By continuing you agree to the use of cookies. ...
In this paper, we determined the optimal flow rate trajectory during the loading phase of a mAb capture column. For this purpose, a multi-objective function was used, consisting of productivity and resin utilization. Several general types of trajectories were considered, and the optimal Pareto points were obtained for all of them. In particular, the presented trajectories include a constant-flow loading process as a nominal approach, a stepwise trajectory, and a linear trajectory. Selected trajectories were then applied in experiments with the state-of-the-art protein A resin mAb Select PrismATM, running in batch mode on a standard single-column chromatography setup, and using both a purified mAb solution as well as a clarified supernatant. The results show that this simple approach, programming the volumetric flow rate according to either of the explored strategies, can improve the process economics by increasing productivity by up to 12% and resin utilization by up to 9% compared to a ...
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. ...
TeledyneIsco announces a first in non-contacting flow measurement technology for open channel applications - laser Doppler velocity measurement. Laser technology penetrates the surface to measure subsurface velocity at multiple points. Before LaserFlow, non-contact sensors only measured surface velocity thereby limiting the flow calculation with... ...
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....
Over the years, Noctua has put itself at the forefront of quiet cooling innovations with its unique, psychoacoustically optimised impeller designs as well as new bearing and drive technologies such as the SSO-Bearing (Self-Stabilising Oil Pressure Bearing) or the Smooth Commutation Drive (SCD) system. Thanks to advanced aerodynamic design measures like Vortex-Control Notches, Flow Acceleration Channels or Inner Surface Microstructures, Noctuas products are renowned for pushing the envelope in axial fan technology.
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…
Free online storage and sharing with Screencast.com. 2 GB of storage and 2 GB of bandwidth per month for free. We wont compress, alter or take ownership of your content.
A student should be able to evaluate the speed of the object in the projectile and study the time of flight using range and horizontal velocity values ...
"Our Bodies' Velocities, By the Numbers". Retrieved 19 August 2016. The [...] blood [...] flow[s] at an average speed of 3 to 4 ... National Heart Lung and Blood Institutde. Retrieved 14 November 2011.. *^ Calculated: 2000 food calories = 2.0×106 cal × 4.184 ... Kinetic energy of the Moon in its orbit around the Earth (counting only its velocity relative to the Earth)[192][193] ... Average kinetic energy of one human red blood cell.[21][22][23] ... The total release velocity is 30.7 m/sec. *^ Calculated: 1/2 × ...
2006 Cited by 262 related articles Ginkgo biloba extract increases ocular blood flow velocity; HS Chung, A Harris, JK ... "Ginkgo biloba Extract Increases Ocular Blood Flow Velocity". Journal of Ocular Pharmacology and Therapeutics. 15 (3): 233-240. ... blood pressure, and retinal blood flow autoregulation: a mathematical model to clarify their relationship and clinical ... Harris was co-chair, World Glaucoma Congress Consensus on Ocular Blood Flow, and is a member of the international faculty board ...
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. ...
Blood flow and physiology[edit]. Blood flow can be visualized and quantified on scans acquired with a scan sequence called 4D ... Visualization can display flow velocity maps, vectors and streamline ... Blood typically appears bright in these sequences due to the contrast properties of blood and its rapid flow. The technique can ... MRA (magnetic resonance angiography) can produce 3D and 4D images of blood vessels and the flow of blood through the vessels. ...
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/ ... However, the velocities of plates range widely. The fastest-moving plates are the oceanic plates, with the Cocos Plate ... Newton's three laws are: A body either is at rest or moves with constant velocity, until and unless an outer force is applied ...
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 ...
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 ...
Studies on the velocity of blood flow: I. The method utilized. J Clin Investigation 1927;4:1-13. Love, William D. (1965). " ... If one is to evaluate ischemia (reductions in coronary blood flow resulting from coronary artery disease) then individuals must ... The movement of Tl-201 reflected differences in tissue delivery (blood flow) and function (mitochondrial activity). The ... as well as the occluded blood vessels and the mass of infarcted and viable myocardium. The usual isotopes for such studies are ...
Droste, D W; Harders, A G; Rastogi, E (August 1989). "A transcranial Doppler study of blood flow velocity in the middle ... Harders, A. G.; Laborde, G.; Droste, D. W.; Rastogi, E. (January 1989). "Brain Activity and Blood flow Velocity Changes: A ... Njemanze PC (September 2004). "Asymmetry in cerebral blood flow velocity with processing of facial images during head-down rest ... derived from Fourier analysis of mean blood flow velocity to trigger target face search from a computerized face database ...
These ultrasonic procedures measure blood flow velocity within the brain's blood vessels. They are used to diagnose embolisms, ... ACG also facilitates blood flow analysis as well as the detection of obstructions in cerebral blood flow (from cerebral ... With a digital signal, it becomes possible to study the patterns of the blood flow moving inside the skull. These patterns form ... With each heartbeat, blood circulates in the skull, following a recurring pattern according to the oscillation produced. This ...
Doppler ultrasound allows for assessment of carotid arterial blood flow. Blood flow velocity is increased in areas of stenosis ... poor blood flow, and deep artery location. CEUS is prone to overinterpretation of vessel wall abnormalities, known as ... During carotid duplex evaluation, the 2D B-mode structural image is superimposed with the doppler flow data, which provides a ... B-mode ultrasound and Doppler ultrasonography to evaluate both structural details of the carotid arteries and blood flow ...
By comparing the phase of successive A-mode scans, the velocity of blood flow can be determined via the Doppler equation. This ... "Noninvasive imaging of in vivo blood flow velocity using optical Doppler tomography". Opt. Lett. 22 (14): 1119-1121. doi: ... An algorithm developed by Jia et al., is used to determine blood flow in the retina. The split-spectrum amplitude decorrelation ... OCTA uses low-coherence interferometry to measure changes in backscattered signal to differentiate areas of blood flow from ...
In a technique known as blue field entoptoscopy, the effect is used to estimate the blood flow in the retinal capillaries. The ... Riva, C. E.; Petrig, B. (1980). "Blue field entoptic phenomenon and blood velocity in the retinal capillaries". Journal of the ... Red blood cells pile up behind the white blood cell, showing up like a dark tail. This behavior of the blood cells in the ... The white blood cells, which are larger than red blood cells, but much rarer and do not absorb blue light, create gaps in the ...
Estimation of blood velocity and turbulence in color flow imaging used in medical ultrasonography. Estimation of target ... Autocorrelation technique described on p.2-11 Real-Time Two-Dimensional Blood Flow Imaging Using an Autocorrelation Technique, ... velocity in pulse-doppler radar A covariance approach to spectral moment estimation, Miller et al., IEEE Transactions on ...
In 1885 he obtained the degree of Doctor of Medicine with a thesis on the velocity of blood flow as detected by a ... Cybulski was one of the first physiologists to register and describe the blood flow linear velocity of the carotid artery and ... Polish pioneer in developing of the device for measuring blood flow velocity". J Physiol Pharmacol. 57 Suppl 1: 107-18. PMID ... Among his other discoveries was establishing that an increase in intracranial pressure causes disturbances in blood flow to the ...
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 ...
"Relationship of 133Xe cerebral blood flow to middle cerebral arterial flow velocity in men at rest". J. Cereb. Blood Flow Metab ... Daly, M.deB., C.J. Lambertsen and A. Schweitzer (August 1953). "Some observations on the carotid body blood flow in the cat". ... "Fast and slow components of cerebral blood flow response to step decreases in end-tidal PCO2 in humans"". J. Appl. Physiol. 85 ... "Observations on the volume of blood flow and oxygen utilization of the carotid body in the cat". J. Physiol. 125 (1): 67-89. ...
"Carotid artery blood flow and middle cerebral artery blood flow velocity during physical exercise". Journal of Applied ... Jørgensen, LG; Perko, M; Hanel, B; Schroeder, TV; Secher, NH (March 1992). "Middle cerebral artery flow velocity and blood flow ... Jørgensen, LG; Perko, G; Secher, NH (November 1992). "Regional cerebral artery mean flow velocity and blood flow during dynamic ... Hypercapnia also stimulates vasodilation of cerebral blood vessels, increased cerebral blood flow and elevated ICP presumably ...
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 ...
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 ...
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 greatest change in blood pressure and velocity of blood flow occurs at the transition of arterioles to capillaries. In a ... The decreased velocity of flow in the capillaries increases the blood pressure, due to Bernoulli's principle. This induces gas ... Blood pressure in the arteries supplying the body is a result of the work needed to pump the cardiac output (the flow of blood ... Any pathology which constricts blood flow, such as stenosis, will increase total peripheral resistance and lead to hypertension ...
However, a particular difficulty of measuring flow velocity in capillaries is caused by the low blood flow rate and micrometre- ... the measurement of blood flow through arteries, capillaries, and veins. Measuring blood velocity in capillaries is an important ... This technique is currently used in biomedicine to measure blood flow in arteries and veins. It is limited to high flow rates ... are several techniques currently being used to measure blood velocity in a clinical setting or other types of flow velocities. ...
This reduces the diameter of distended veins and increases venous blood flow velocity and valve effectiveness. Compression ... Deep vein thrombosis occurs when blood flow decreases (especially in the lower extremities), causing blood to pool in the legs ... As a result, the arterial pressure is increased, which causes more blood to return to the heart and less blood to pool in the ... Doctors will typically recommend these stockings for those who are prone to blood clots, lower limb edema, and blood pooling in ...
... 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 ...
A pattern of blood-flow-velocity changes is obtained in response to questions that include correct and incorrect answers. The ... William Moulton Marston studied blood-pressure and noted increase in systolic blood pressure of 10 mm Hg or over indicated ... While taking a polygraph test the subject wears a blood pressure device to measure blood pressure fluctuations. Respiration is ... Marston determined systolic blood-pressure by oscillatory methods and his findings cite definite changes in blood pressure ...
It can also show decreased opening of the mitral valve leaflets, and increased blood flow velocity during diastole. The trans- ... to allow blood to flow from the left atrium to the left ventricle. A normal mitral valve will not impede the flow of blood from ... The loss of the atrial kick due to atrial fibrillation ( i.e. blood cannot flow into the left ventricle thus accumulating in ... the valve causes an impediment to the flow of blood into the left ventricle, creating a pressure gradient across the mitral ...
... red cells are distributed in the axial core and their mean velocity is therefore more than the mean velocity of blood. There is ... "Capillary blood flow: II. Deformable model cells in tube flow". Microvascular Research. 2 (4): 420-433. doi:10.1016/0026-2862( ... Considering steady laminar fully developed blood flow in a small tube with radius of r 0 {\displaystyle r_{0}} , whole blood ... Blood flow in microvascular networks: Experiments and simulation. Circulation Research 67:826-834, 1990. C. Kleinstreuer, (2007 ...
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[ ...
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] ...
... blood and lung vasculature,[50] and other branching patterns in nature can be modeled on a computer by using recursive ... "A Public Turbulence Database Cluster and Applications to Study Lagrangian Evolution of Velocity Increments in Turbulence". ... Surfaces in turbulent flows[73][74]. *Trees. *Dust grains[75]. *Brownian motion (generated by a one-dimensional Wiener process ... blood vessels, pulmonary structure,[50] etc. or turtle graphics patterns such as space-filling curves and tilings ...
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 ...
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 ...
Cerebral autoregulation refers to the physiological process that maintains stable cerebral blood flow (CBF) during changes in ... Autoregulation of cerebral blood flow in experimental focal brain ischemia. J. Cereb. Blood Flow Metab. 10:327-336, 1990. ... Mader, G., Olufsen, M. & Mahdi, A. Modeling Cerebral Blood Flow Velocity During Orthostatic Stress. Ann Biomed Eng 43, 1748- ... Dynamic regulation of middle cerebral artery blood flow velocity in aging and hypertension. Stroke 31:1897-1903, 2000. ...
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 ...
The candidate maximal flow velocity waveform with the highest signal quality index is finally selected. Results: We evaluated ... However, due to the low signal-to-noise ratio of TCD spectrograms, measuring the maximal flow velocity is challenging. In this ... we propose a calibration-free algorithm for estimating maximal flow velocities from TCD spectrograms and present a pertaining ... maximal flow velocity waveforms) via an edge-following step that incorporates physiological constraints. ...
We estimate the velocity field of the blood flow in a human face from videos. Our approach first performs spatial preprocessing ...
... 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 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 ( ...
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 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 ...
... 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- ...
... Jan 1, 1998 , Magazine: ... Time domain ultrasonography is an alternative to Doppler analysis of blood flow direction and velocity. The time domain ... We first estimated flow velocity using time domain ultrasonography and immediately after pulsed Doppler was used. The ... that time domain ultrasonography seems to be a valid technique for imaging fetal vessels and for measuring blood flow velocity. ...
Doppler ultrasound, Blood flow velocity, Reproducibility, Uterine artery. in Ultrasound in Obstetrics & Gynecology. volume. 17 ... CONCLUSION: As the effect of repetition on the results of Doppler measurements of uterine artery blood flow velocity is large, ... CONCLUSION: As the effect of repetition on the results of Doppler measurements of uterine artery blood flow velocity is large, ... Intraobserver reproducibility of Doppler measurements of uterine artery blood flow velocity in premenopausal women. Valentin, ...
... 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 ...
Robust Blood Flow Velocity Estimation from 3D Rotational Angiography. Marco Bögel, Sonja Gehrisch, Thomas Redel, Christopher ... Robust Blood Flow Velocity Estimation from 3D Rotational Angiography. In 2018 IEEE International Conference on Image Processing ...
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- ...
J. N. W. West, M. S. Salih, W. A. Littler; Doppler Characterization of the Immediate Blood Flow Velocity Pattern after Release ... Doppler Characterization of the Immediate Blood Flow Velocity Pattern after Release of Prolonged Venous Occlusion of the ... 2. The response consists of an early, vasodilatory, increase in flow and is followed by a decrease in flow relative to control ... 1. There is a biphasic flow response measured plethysmographically after release of prolonged venous occlusion of the forearm. ...
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); ...
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 ...
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 ...
Developmental changes in cerebral and visceral blood flow velocity in healthy neonates and infants ... Developmental changes in cerebral and visceral blood flow velocity in healthy neonates and infants. ... Developmental changes in cerebral and visceral blood flow velocity in healthy neonates and infants. Journal of Ultrasound in ...
  • described an ultrasonic flowmeter, based on the Doppler effect, which could continuously record arterial or venous blood flow velocity through the intact human skin. (thejns.org)
  • 2 Recently the use of a Doppler ultrasonic flow detector has proved to be an extremely sensitive method for detecting intracardiac air emboli. (thejns.org)
  • Xenon blood flow ( 5 ) and transcranial Doppler ultrasound (TCD) studies indicate that patients with type 2 diabetes have impaired cerebrovascular reactivity to hypercapnia ( 6 , 7 ). (diabetesjournals.org)
  • Estimated IQ and markers of coagulation and endothelial activation, hemolysis, and inflammation, as well as transcranial Doppler velocities, hydroxyurea use, and demographic information were obtained. (hindawi.com)
  • Overt stroke risk can be demonstrated by elevation of blood flow velocity measured by transcranial Doppler ultrasonography (TCD). (hindawi.com)
  • Objective: Novel applications of transcranial Doppler (TCD) ultrasonography, such as the assessment of cerebral vessel narrowing/occlusion or the non-invasive estimation of intracranial pressure (ICP), require high-quality maximal flow velocity waveforms. (embs.org)
  • Quantification of left-to-right shuntting and defect size after balloon mitral commissuratomy using biplane transesophageal echocardiography, color flow Doppler mapping, and the principle of proximal flow convergence. (springer.com)
  • Methods --Continuous middle cerebral artery blood flow velocity (BFV) (transcranial Doppler ultrasound) and mean arterial pressure (MAP, Finapres) were measured in response to (1) acute hypotension during standing, (2) steady-state sitting and standing, and (3) hypercarbia during CO 2 rebreathing in 10 healthy young subjects (age 24±1 years), 10 healthy elderly subjects (age 72±3 years), and 10 previously treated hypertensive elderly (age 72±2 years) subjects. (ahajournals.org)
  • The availability of transcranial Doppler (TCD) ultrasonography for the noninvasive measurement of beat-to-beat changes in cerebral blood flow velocity (BFV) has made it possible to assess cerebral autoregulation under both steady-state and dynamic conditions. (ahajournals.org)
  • A study was carried out using Doppler ultrasound measurements of cerebral blood flow velocities (CBFV) as an indicator of alterations in cerebral haemodynamics. (bmj.com)
  • Intracoronary peak blood flow velocity in either the left anterior descending or left circumflex artery was measured by continuous Doppler signal recording, heart rate, central aortic blood pressure, and adverse effects were recorded. (biomedsearch.com)
  • Time domain ultrasonography is an alternative to Doppler analysis of blood flow direction and velocity. (cun.es)
  • This study was undertaken to validate this technique for measuring peak systolic velocity compared to the pulsed-wave Doppler method in human fetuses. (cun.es)
  • We first estimated flow velocity using time domain ultrasonography and immediately after pulsed Doppler was used. (cun.es)
  • OBJECTIVE: To determine the intraobserver repeatability of Doppler measurements of uterine artery blood flow velocity and the contribution of various factors to within-subject variance. (lu.se)
  • CONCLUSION: As the effect of repetition on the results of Doppler measurements of uterine artery blood flow velocity is large, the average of several repeat measurements should be used to enhance measurement reproducibility. (lu.se)
  • article{1599421d-b125-405b-a65f-7b0867d26f81, abstract = {OBJECTIVE: To determine the intraobserver repeatability of Doppler measurements of uterine artery blood flow velocity and the contribution of various factors to within-subject variance. (lu.se)
  • Doppler recordings of blood flow velocity during hyperemia were analysed in the brachial artery. (diva-portal.org)
  • 5. Our data confirmed the hypothesis of Caro, Foley & Sudlow [ Journal of Physiology (London) (1970), 207 , 257-269] that there is a constant and definite latency preceding the onset of vasodilatory flow, as reflected by changes in Doppler velocities. (portlandpress.com)
  • 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)
  • The outcome measures were assessed with color flow Doppler ultrasound. (jaoa.org)
  • 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. (bmj.com)
  • Doppler optical coherence tomography (OCT) is a noninvasive imaging modality that provides quantitative flow information with high spatial and temporal resolution. (osapublishing.org)
  • Blood flow velocity in the ophthalmic arteries was assessed by means of colour Doppler imaging (CDI). (bmj.com)
  • In addition, coronary flow velocity was measured in the same patients using a modified transthoracic Doppler assessment of the left anterior descending artery. (uib.no)
  • We found a moderate but statistically significant correlation between flow velocity assessed by trans thoracic Doppler and the proposed method applying both Spearman and Pearson tests. (uib.no)
  • Conclusion: Measures of coronary flow velocity using a novel fully automatic method that utilizes the information from the X-ray coronary angiographic sequence were statistically significantly correlated to measurements obtained with transthoracic Doppler recordings. (uib.no)
  • Different flow patterns between left and right internal thoracic artery grafts influence the evaluation of severe graft stenosis by transthoracic Doppler echocardiography. (semanticscholar.org)
  • Transcranial Doppler ultrasonography (TCD) is a noninvasive technique that offers reliable measurement of CBF velocity, [11,12] CO 2 vasoreactivity, [13] and autoregulation. (asahq.org)
  • Septal arterial blood flow velocities were measured with a 20-MHz, 80-channel ultrasound pulsed Doppler velocimeter. (onlinejacc.org)
  • The relationship of blood velocity as measured by transcranial doppler ultrasonography to cerebral blood flow as determined by stable xenon computed tomographic studies after aneurysmal subarachnoid hemorrhage. (semanticscholar.org)
  • Fully distributed absolute blood flow velocity measurement for middle cerebral arteries using Doppler optical coherence tomography. (escholarship.org)
  • Doppler optical coherence tomography (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy. (escholarship.org)
  • Assessment of blood flow velocity in Doppler images is of great importance in clinical studies and research. (city.ac.uk)
  • From the Doppler waveform envelope, numerous indices can be obtained, such as the pulsatility index, resistance index, and systolic/diastolic ratio, as well as acceleration of the blood through valves. (city.ac.uk)
  • We present the theory and implementation of our methodology, and demonstrate its ability to accurately trace the blood flow velocity in pulse wave Doppler images as well as its robustness to noise and computational efficiency. (city.ac.uk)
  • Antenatally, all had absent or reversed diastolic flow on Doppler ultrasound of the umbilical artery (UA). (biomedcentral.com)
  • Doppler studies of the utero-placental circulation in growth restricted fetuses have shown circulatory redistribution with an increased blood flow velocity in the cerebral circulation and a reduced blood flow velocity in the aorta [ 1 ]. (biomedcentral.com)
  • Postnatally, blood velocity waveforms were obtained from the superior mesenteric artery using a duplex ultrasound imaging and Doppler system (Hewlett Packard Sonos 100 with 7.5 MHz imaging and 5.0 MHz Doppler transducer). (biomedcentral.com)
  • Diagnostic blood flow monitoring during therapeutic interventions using color Doppler optical coherence tomography. (russianpatents.com)
  • The amount of blood flow is determined by the Doppler shift of the frequency imposed on postoyanniye be attributed to the difficulty of manufacturing the scanner unit reference reflector. (russianpatents.com)
  • Children at risk of CVA can be identified using transcranial Doppler ultrasonography which enables evaluation of cerebral artery blood flow velocity with a sensitivity of ninety percent and specificity of one hundred percent when compared with cerebral angiography. (mjhid.org)
  • To evaluate with Doppler method the dynamics of blood flow velocity changes within and outside the blood supply area of ischaemic focus forty-one patients admitted to hospital within 24 hours of tomographically confirmed ischaemic stroke confined to the common carotid artery territory were studied. (viamedica.pl)
  • Doppler examination reveals improvement in blood flow in these arteries and development of collateral blood supply in consecutive days. (viamedica.pl)
  • The technique is based on optical Doppler tomography (ODT), which combines Doppler velocimetry with optical coherence tomography to measure blood flow velocity at discrete spatial locations. (osapublishing.org)
  • The magnetic resonance ascending aortic regurgitant fraction was compared with Doppler echocardiographic descending aortic flow velocity patterns. (nih.gov)
  • Pulsedwave Doppler sampling of descending aortic flow reflects severity of aortic regurgitant disease, in part the result of more uniform blood-velocity profiles in the descending aorta compared with the ascending aorta. (nih.gov)
  • The Doppler end-diastolic velocity in the descending aorta is a useful parameter of severity of aortic regurgitation. (nih.gov)
  • We have developed digital, Apple II microcomputer-based methods for the numerical analysis of pulsed, range-gated, ultrasonic Doppler blood velocity signals. (nih.gov)
  • This was achieved by recording numerical values for the flow, volume, and velocity of erythrocytes using the laser-Doppler flowmeter. (naver.com)
  • Observations on cochlear blood flow using the laser Doppler method in guinea pigs. (naver.com)
  • Serial assessment of laser Doppler flow during acute pain crises in sickle cell disease. (naver.com)
  • Orbital Doppler evaluation of blood flow velocities in optic neuritis. (msdiscovery.org)
  • In preliminary Doppler sonographic studies of healthy young women, it was demonstrated that the clitoral arterial blood flow increases following vaginal pressure stimulation, [ 34 ] slightly increases at the ovulation phase of menstrual cycle, [ 35 ] and significantly increases in women taking hormonal contraception. (medscape.com)
  • In this study, we compare breath-hold high temporal resolution (19ms) spiral phase velocity mapping of proximal left and right coronary blood flow velocity with invasive gold-standard Doppler Flowire measurements in a small group of patients. (ismrm.org)
  • As expected, MR velocities are lower than Doppler velocities (by 47% on average) but the temporal flow patterns are similar (R2 = .47 - .91). (ismrm.org)
  • A numerical experiment was performed for 2D-UMI simulation of blood flow models in a straight vessel with inflow velocity profiles symmetric and asymmetric to the vessel axis using existing evaluation functions based on Doppler velocity error for the inflow velocity estimation. (elsevier.com)
  • 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)
  • In vivo measurement of retinal blood flow is obtained by measuring the blood velocity of erythrocytes and lumen diameters of the blood vessels using an adaptive optics scanning laser ophthalmoscope. (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)
  • For gestational age, birth weight and blood flow velocity there was one measurement per baby. (biomedcentral.com)
  • 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)
  • This PC-based micro-vessel velocity measurement enables the development of the single-vessel CBF-fMRI method. (rxivist.org)
  • Most importantly, the measurement of retinal blood flow velocity and flow volume in the small retinal vessels enables the estimate of the retinal tissue perfusion. (biomedcentral.com)
  • Two-dimensional ultrasonic-measurement-integrated (2D-UMI) simulation can correctly reproduce an intravascular blood flow field and hemodynamics by feeding back an ultrasonic measurement to the numerical blood flow simulation. (elsevier.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)
  • 2009. ISBN 90-6299-222-6 Optic nerve blood flow measurement. (wikipedia.org)
  • We evaluated experimentally the projective flow estimation method and the re-projection method. (spie.org)
  • This includes synthetic aperture imaging using either spherical or plane waves with velocity estimation performed with directional beamforming or speckle tracking. (dtu.dk)
  • A method for extending the 2D TO method to 3D vector velocity estimation is presented and the implications for future vector velocity imagi- g is indicated. (dtu.dk)
  • Blood velocity estimation is central in assessing coronary flow reserve. (uib.no)
  • Methods and Results: A multi-step automatic method for blood flow velocity estimation based on the information extracted solely from the cine X-ray coronary angiography sequence obtained by invasive selective coronary catheterization was developed. (uib.no)
  • Here we describe the combination of a confocal laser scanning system and an image analysis software package that allows rapid and reproducible estimation of leukocyte velocities in microvessels. (ulster.ac.uk)
  • Raghavendra, P. / Evaluation of the performance of strategies for the estimation of low velocity blood flow . (elsevier.com)
  • However, systematic study has not been done on the relative validity and effectiveness of existing inflow velocity estimation methods for various target flow fields. (elsevier.com)
  • As a result, it was clarified that a significantly large estimation error occurs in the asymmetric flow due to a nonfeedback domain near the downstream end of the calculation domain. (elsevier.com)
  • Hence, a new inflow velocity estimation method of 2D-UMI simulation is proposed in which the feedback and evaluation domains are extended to the downstream end. (elsevier.com)
  • Measurements of left and right ventricular stroke corresponded closely with those of aortic (r=0.98) and pulmonary flow (r=0.99) respectively, and Qp : Qs flow ratios agreed with stroke volume ratios (r=0.92). (springer.com)
  • Antman EM, Marsh JD, Green LH, Grossman W. Blood oxygen measurements in the assessment of intracardiac left to right shunts: a critical appraisal of methodology. (springer.com)
  • The approach has been thoroughly investigated using both simulations, flow rig measurements, and in-vivo validation against MR scans. (dtu.dk)
  • RESULTS: The effect of sampling site on measurements of peak systolic velocity and time-averaged maximum velocity was non-significant, but pulsatility index values obtained at the distal sampling site were slightly higher than those obtained at the other sites (P = 0.01). (lu.se)
  • Averaging the results of the three repeat measurements yielded increased intraclass correlation coefficients: 0.79-0.89 for peak systolic velocity, 0.80-0.92 for time-averaged maximum velocity and 0.86-0.93 for pulsatility index. (lu.se)
  • This approach provides high temporal bandwidth measurements, allowing the fluctuation of blood flow during cardiac cycles to be measured. (osapublishing.org)
  • These methodologies are advantageous, as they allow measurements to be determined during the exercise, without the need to stop contractions, and no increases in blood pressure are observed with l -NMMA ( 4 ). (diabetesjournals.org)
  • We are currently investigating whether incorporation of more realistic aortic root velocity measurements, obtained using phase-contrast magnetic resonance imaging (PC-MRI), into these simulations can improve the correlation with disease. (asme.org)
  • Here we introduce cerebral blood flow (CBF)-fMRI, which uses high-resolution phase-contrast MRI to form velocity measurements of flow and demonstrate CBF-fMRI in single penetrating microvessels across rat parietal cortex. (rxivist.org)
  • Coronary flow measurements can provide important information, e.g. to assess coronary stenosis, but remain challenging due to the need for high spatio-temporal resolution in the presence of heart and respiratory motion. (ismrm.org)
  • 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. (elsevier.com)
  • Higgins, Charles B. / Breath-hold MR measurements of blood flow velocity in internal mammary arteries and coronary artery bypass grafts . (elsevier.com)
  • Our results show that time domain ultrasonography seems to be a valid technique for imaging fetal vessels and for measuring blood flow velocity. (cun.es)
  • 2. The response consists of an early, vasodilatory, increase in flow and is followed by a decrease in flow relative to control, thought to be mediated by myogenic contraction of resistance vessels. (portlandpress.com)
  • It has been suggested by Caro, Foley & Sudlow [ Journal of Physiology (London) (1970), 207 , 257-269] that there is a delay of up to five systolic beats before vasodilatation takes place, leading to their suggestion that the vasodilatation is passive and secondary to an increased flow through emptied capacitance vessels. (portlandpress.com)
  • Mean velocity is not related to unique moments in the cardiac cycle and seems to reflect even more closely blood cell velocity in capillary vessels. (bmj.com)
  • Assessment using RFI provides useful information and may contribute to the further understanding of hemodynamics in the retina blood vessels. (arvojournals.org)
  • The technique is most applicable to medium-sized blood vessels. (osapublishing.org)
  • Circulation is the movement of blood through blood vessels, from the heart and then back to the heart. (lubopitko-bg.com)
  • An obese person is apt to have high blood pressure because about 200 miles of additional blood vessels develop for each extra pound of fat. (lubopitko-bg.com)
  • Velocity changes according to the total crosssectional area of vessels. (lubopitko-bg.com)
  • Current color flow mapping systems are limited in their ability to detect slow blood flow, and to accurately estimate flow velocities in a region that contains vessels with rapid flow as well as slow blood flow. (elsevier.com)
  • The objective of the study was to determine the pattern of distribution of blood flow, volume, and velocity of erythrocytes circulating in blood vessels of the tympanic membrane. (naver.com)
  • 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. (elsevier.com)
  • If one assumes an internal diameter of 4 mm, the calculated mean blood flow velocity within the vessel is 50 cm/sec. (thejns.org)
  • V max = maximum blood flow velocity , V mean = mean of velocities across vessel lumen. (thejns.org)
  • 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)
  • 4 The velocities measured in each visible vessel were averaged. (bmj.com)
  • Although the ophthalmic artery is the only routinely assessed retrobulbar vessel in CDI which does not enter the eye, its contribution to choroidal blood flow is important. (bmj.com)
  • Velocity, vessel diameter, Circulatory resistance in the region extending from the common cartid artery to the peripheral cerebral artery, was calculated. (nii.ac.jp)
  • Blood pressure is the force of blood against a blood vessel wall. (lubopitko-bg.com)
  • Another factor that determines blood pressure is peripheral resistance , which is the friction between blood and the walls of a blood vessel. (lubopitko-bg.com)
  • All things being equal, the smaller the blood vessel, the greater the resistance and the higher the blood pressure. (lubopitko-bg.com)
  • Similarly, total blood vessel length increases blood pressure because a longer vessel offers greater resistance. (lubopitko-bg.com)
  • The exceptionally high resolution of ODT permits noninvasive in vivo imaging of both blood microcirculation and tissue structures surrounding the vessel, which has significance for biomedical research and clinical applications. (osapublishing.org)
  • Summary We established a high-resolution PC-based single-vessel velocity mapping method using the high field MRI. (rxivist.org)
  • The aim of this study was to examine the existing methods systematically and to establish a method to accurately estimate inflow velocities for various vessel geometries and flow conditions in 2D-UMI simulations. (elsevier.com)
  • Further numerical experiments of 2D-UMI simulation for two realistic vessel geometries of a healthy blood vessel and a stenosed one confirmed the effectiveness of the proposed method. (elsevier.com)
  • abstract = "We applied frequency domain analysis to detect and quantify spontaneous fluctuations in the blood flow velocity of the middle cerebral artery (MCAFV). (elsevier.com)
  • 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)
  • 1. There is a biphasic flow response measured plethysmographically after release of prolonged venous occlusion of the forearm. (portlandpress.com)
  • 3. Methodological constraints with the technique of forearm plethysmography have to date precluded an individual beat-by-beat examination of this response, in particular for resolving the question of the immediate flow pattern after release of venous occlusion. (portlandpress.com)
  • 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)
  • 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. (bmj.com)
  • CBFV (cerebral blood flow velocity) is lower in the morning than in the afternoon and evening. (biomedcentral.com)
  • It has been well documented that cerebral blood flow velocity (CBFV) is lower in sleep [ 1 - 7 ] and in the morning shortly after awakening [ 8 - 10 ] than in the afternoon or evening. (biomedcentral.com)
  • 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). (arvojournals.org)
  • To study the physiological effects of sleep apnea on cerebral blood flow velocity (CBFV), CBFV was measured in subjects simulating apnea. (tdl.org)
  • The clinical courses of 8 term infants with focal cerebral infarction or neonatal stroke were studied to determine whether such infants can be identified by current markers of perinatal distress, and whether changes in cerebral blood flow velocity (CBFV) occur during the acute phase of the disease. (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)
  • 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)
  • 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 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)
  • 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)
  • Sassoon DJ, Fujiwara T, Mitchell MB, Di Maria M, Barker AJ, Browne LP. Novel application of 4D flow magnetic resonance imaging in a neonatal post-operative aortic dissection. (ucdenver.edu)
  • Responses of cerebral blood flow to the postural unloading maneuver in aortic stenosis (AS) have not been described so far. (viamedica.pl)
  • 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)
  • 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)
  • Peak systolic velocity, time-averaged maximum velocity, and pulsatility index were calculated. (lu.se)
  • The pulsatility index and the time-averaged maximum velocity were calculated. (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)
  • 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)
  • 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)
  • 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)
  • In vitro flow visualization studies have suggested the presence of a large anterior vortex inside the left ventricle during mitral inflow. (onlinejacc.org)
  • During mid-diastolic diastasis, mitral inflow ceased until the flow accelerated again at atrial systole. (onlinejacc.org)
  • In the presence of severe coronary artery stenosis, intraaortic balloon pumping failed to increase diastolic inflow to the myocardium and did not enhance systolic retrograde flow from the myocardium to the extramural coronary artery. (onlinejacc.org)
  • In this method, it is critically important to give the correct cross-sectional average inflow velocity (inflow velocity) as the boundary condition. (elsevier.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)
  • The temporal pattern of coronary flow velocity through the cardiac cycle provides important information about coronary haemodynamics and atherosclerotic disease state. (ismrm.org)
  • We conclude that spiral phase velocity mapping has the potential to assess temporal patterns of coronary flow velocity non-invasively. (ismrm.org)
  • Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle. (ahajournals.org)
  • The candidate maximal flow velocity waveform with the highest signal quality index is finally selected. (embs.org)
  • There is also a typical change in velocity waveform after exercise. (muni.cz)
  • Conclusion: The most altered parameter is mean blood flow velocity, which corresponds to an observed change of velocity waveform probably caused by local vasodilatation lasting only for several seconds. (muni.cz)
  • 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. (bmj.com)
  • We sought to evaluate the effect of intraaortic balloon pumping on the phasic blood velocity waveform into myocardium with severe coronary artery stenosis. (onlinejacc.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)
  • This study examined the effect of local infusion of an NOS inhibitor on skeletal muscle glucose uptake (2-deoxyglucose) and capillary blood flow (contrast-enhanced ultrasound) during in situ contractions in rats. (diabetesjournals.org)
  • 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)
  • More important than the systolic and diastolic pressure is the mean arterial blood pressure (MABP) . (lubopitko-bg.com)
  • Arterial blood flow velocity was correlated neither with thickness nor with volume of the central retina. (arvojournals.org)
  • 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)
  • In this work, we propose a calibration-free algorithm for estimating maximal flow velocities from TCD spectrograms and present a pertaining beat-by-beat signal quality index. (embs.org)
  • 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)
  • Estimating the coronary blood velocity is a key approach in investigating patients with angina pectoris and no significant coronary artery disease. (uib.no)
  • Assess the effect of Ticagrelor compared to placebo on the adenosine induced coronary blood flow velocity response by estimating the change in area under the adenosine dose response curve before and after study drug. (clinicaltrials.gov)
  • To determine the inter-visit variability of retinal blood flow velocities (BFVs) using a retinal function imager (RFI) in healthy young subjects. (biomedcentral.com)
  • A number of methods for ultrasound vector velocity imaging are presented in the paper. (dtu.dk)
  • The transverse oscillation (TO) method can estimate the velocity transverse to the ultrasound beam by introducing a lateral oscillation in the received ultrasound field. (dtu.dk)
  • 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)
  • A blood flow detection and imaging method and system is described for displaying images in accordance with signals transmitted from an intravascular ultrasound transducer probe. (google.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)
  • However, due to the low signal-to-noise ratio of TCD spectrograms, measuring the maximal flow velocity is challenging. (embs.org)
  • The objective of this study was to assess the feasibility and accuracy of magnetic resonance (MR) velocity mapping to calculate pulmonary-to-systemic flow ratio (Qp : Qs) in patients with a suspected or diagnosed atrial-level shunt. (springer.com)
  • OBJECTIVE: Cardiovascular (CV) risk relates to the blood flow velocity pattern in the brachial artery during hyperemia, especially to the hyperaemic systolic to diastolic mean blood flow velocity (SDFV) ratio. (diva-portal.org)
  • CONCLUSION: Our results indicate that the hyperemic systolic to diastolic blood flow velocity ratio in the brachial artery is related to atherosclerosis in the carotid artery. (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)
  • The standard apical four chamber view was used to observe the changes of E peak, A peak, and velocity-time integral (VTI) ratio of tricuspid blood flow during the strain phase and release phase of the Valsalva maneuver. (scirp.org)
  • Paired t-test was used to compare E peak, A peak, and VTI ratio of tricuspid blood flow during the different phases. (scirp.org)
  • Relative myocardial blood volume (rBV), exchange flow velocity (β), myocardial blood flow (MBF), MBF reserve (MFR) and endocardial-to-subepicardial (endo-to-epi) MBF ratio were measured from the steady state and contrast replenishment time-intensity curves. (bmj.com)
  • Equations of Uniform Motion: If v {\displaystyle \mathbf {v} } = final and initial velocity, t {\displaystyle t} = time, and s {\displaystyle \mathbf {s} } = displacement, then: s = v t {\displaystyle \mathbf {s} =\mathbf {v} t} Modern kinematics developed with study of electromagnetism and refers all velocities v to their ratio to speed of light c. (wikipedia.org)
  • Methods: Our algorithm performs multiple binary segmentations of the TCD spectrogram and then extracts the pertaining envelopes (maximal flow velocity waveforms) via an edge-following step that incorporates physiological constraints. (embs.org)
  • The velocity waveforms and ECG were continuously measured in six putatively healthy young subjects for 130 s during passive postural changes in supine and 90 degrees head-up-tilt (HUT), respectively. (iium.edu.my)
  • 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. (ahajournals.org)
  • Peak red cell velocity was observed in midsystole in small arterioles and capillaries, and in late systole in small venules. (ahajournals.org)
  • To examine the repeatability of and changes in retinal blood velocity (RBV) in the macular capillaries of retinitis pigmentosa (RP) participants in a randomized controlled trial evaluating the efficacy of Transcorneal Electrical Stimulation (TES) for improving visual function. (arvojournals.org)
  • Blood flow velocity in nailfold capillaries was assessed in one randomly chosen finger of the right hand (totally arbitrary choice) by means of nailfold capillaroscopy. (bmj.com)
  • Linear correlations between blood cell velocity in nailfold capillaries and ophthalmic artery were assessed (Spearman's rank order correlation factor). (bmj.com)
  • The mean blood cell velocity in nailfold capillaries was 0.45 (SD 0.32) mm/s. (bmj.com)
  • p=0.007) correlated with blood cell velocity in nailfold capillaries. (bmj.com)
  • The velocity of blood flow is slowest in the capillaries. (lubopitko-bg.com)
  • The slow rate of blood flow in the capillaries is beneficial because it allows time for the exchange of gases in pulmonary capillaries and for the exchange of gases and nutrients for wastes in systemic capillaries. (lubopitko-bg.com)
  • The invention relates to medical instrumentation and can be used to control blood flow in the capillaries of the superficial tissues of man and experimental animals. (russianpatents.com)
  • 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. (ahajournals.org)
  • During vasodilation following dilazep (50 micrograms/kg, i.v.), an adenosine potentiator, red cell velocity increased throughout the entire cardiac cycle in epimyocardial microvessels with significant increases in the total area under the velocity curves accompanied by significant dilation of the arterioles. (ahajournals.org)
  • p=0.09) did not correlate with nailfold capillary blood cell velocity. (bmj.com)
  • The results suggest a relation between nailfold capillary blood cell velocity and blood flow velocity in the ophthalmic artery. (bmj.com)
  • 7 RI and PSV did not correlate with nailfold capillary blood cell velocity. (bmj.com)
  • The relatively constant blood flow during the diastole might predict more closely blood cell velocity in the capillary bed. (bmj.com)
  • Interferometric observations of red blood cell velocity variations, in a near-wall vicinity at small velocities, were compared to limiting values predicted from continuous velocity profile considerations coupled with a plasma no-slip boundary condition. (iospress.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)
  • 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)
  • 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)
  • OBJECTIVE -Diabetes increases the risk for cerebromicrovascular disease, possibly through its effects on blood flow regulation. (diabetesjournals.org)
  • Regadenoson, a selective A2A adenosine receptor agonist, causes dose-dependent increases in coronary blood flow velocity in humans. (biomedsearch.com)
  • Vein blood velocity increases with the increase of the central retinal volume. (arvojournals.org)
  • Conversely, blood flow increases as venules combine to form veins, and velocity is faster in the venae cavae than in the smaller veins. (lubopitko-bg.com)
  • Conclusions: These data support previous findings of significant increases in intestinal blood flow in preterm infants during the first week of life, and of inconsistent effects of enteral feeding volumes on fasting or preprandial intestinal blood flow. (elsevier.com)
  • The reasons for, and the clinical implications of, attenuated increases in postnatal intestinal blood flow in infants on CPAP or HAL require further investigation. (elsevier.com)
  • We allowed exercise to take place for 10 min before starting the infusion of l -NMMA (or saline) so that normal increases in leg glucose uptake (∼30-fold) and leg blood flow (∼10-fold) could take place before the infusions began. (diabetesjournals.org)
  • Diabetic neuropathy, which is the most frequent and earliest diabetes complication, decreases the quality of life and increases the morbidity of diabetic patients ( 1 ) and occurs because of the impairment of nerve blood flow and metabolic imbalances in the neural compartment of the peripheral nerve. (diabetesjournals.org)
  • The purpose of this study is to determine if Ticagrelor increases the Adenosin induced coronary blood flow velocity. (clinicaltrials.gov)
  • An object's momentum increases with the object's mass and with its velocity. (wikipedia.org)
  • Foetal middle cerebral artery peak systolic velocity demonstrated simple continues increase and strong positive correlation with gestational age. (ajol.info)
  • Retinal thickness/volume parameters were obtained by SLO-OCT. Analysis of correlation between retinal blood flow velocity and SLO-OCT findings was performed. (arvojournals.org)
  • The analysis of correlation between retinal blood flow and central retinal thickness/volume (5X5 mm grid pattern) showed a strong correlation between the average blood flow velocity in retinal veins and central retinal volume. (arvojournals.org)
  • mean diastolic blood pressure 73.4 (13.6) mm Hg) did not vary significantly during blood flow assessments. (bmj.com)
  • Mean intra-aneurysmal flow velocities and WSS were significantly reduced in all aneurysms. (epfl.ch)
  • Blood flow velocity in retinal veins, analyzed by RFI, significantly correlates with the volume of central retina. (arvojournals.org)
  • The blood flow velocity standard deviations differed significantly between the two groups so Satterthwaite's method to perform a t-test was used as this does not assume the same standard deviation in each group. (biomedcentral.com)
  • 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)
  • Unilateral intramuscular injection of EPCs into hindlimb skeletal muscles significantly ameliorated impaired sciatic motor nerve conduction velocity and sciatic nerve blood flow in the EPC-injected side of streptozotocin-induced diabetic nude rats compared with the saline-injected side of diabetic nude rats. (diabetesjournals.org)
  • 15 ) showed that vascular endothelial growth factor (VEGF) gene transfer significantly increased nerve conduction velocity and nerve blood flow as well as the amount of vasculature in the muscles and nerves, suggesting that the induction of local angiogenesis ameliorates experimental neuropathy. (diabetesjournals.org)
  • Evans blue dye has been injected to demonstrate the flow patterns. (thejns.org)
  • We quantitated phasic epimyocardial microcirculatory coronary blood flow velocity patterns in the beating left ventricle. (ahajournals.org)
  • Pre- and post-treatment haemodynamics were compared, including mean and maximal velocities, wall-shear stress (WSS) and intra-aneurysmal flow patterns. (epfl.ch)
  • Changes in flow patterns were recorded in only one case. (epfl.ch)
  • One aneurysm remaining patent after 1 year showed no change in flow patterns. (epfl.ch)
  • We investigated the relationship between blood flow velocity and the following variables: birth weight, gestational age, feeding volumes, number of days to reach full feeding volumes, type of feeding given, continuous positive airway pressure (CPAP) administration and hyperalimentation (HAL) administration. (elsevier.com)
  • Magnetic resonance velocity mapping: Clinical application of a new technique. (springer.com)
  • Several clinical examples of complex flow in e.g. bifurcations and around valves have been acquired using a commercial implementation of the method (BK Medical ProFocus Ultraview scanner). (dtu.dk)
  • 3D-printed, patient-specific intracranial aneurysm models: From clinical data to flow experiments with endovascular devices. (ucdenver.edu)
  • Objectives: To identify demographic and clinical variables that relate to the postnatal increase in intestinal blood flow velocity in preterm infants. (elsevier.com)
  • The aim of this study is to evaluate the association of intraocular pressure (IOP) and superior ophthalmic vein blood flow velocity (SOV-BFV) with the clinical features of Graves' orbitopathy. (gazi.edu.tr)
  • Alon Harris, MS, PhD, FARVO is an internationally-active clinical scientist, professor of ophthalmology, educator, inventor and researcher in the field of ocular blood flow and its relationship to diseases of the eye. (wikipedia.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)
  • 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)
  • This technique is a rapid and effective method for the noninvasive assessment of blood flow velocity in IMA grafts. (elsevier.com)
  • thus, there may be some relationship between blood flow velocity and blood pressure or cardiac output. (biomedcentral.com)
  • We propose a system to estimate blood flow velocity in angiographic image data for patient-specific blood flow simulations. (spie.org)
  • Cerebral microvascular disease in diabetes has been attributed to the effects of chronic hyperglycemia on capillary structure ( 2 ), endothelial reactivity ( 3 ), and blood-brain barrier permeability, thus affecting regional metabolism and blood flow regulation ( 4 ). (diabetesjournals.org)
  • We aimed to determine whether there is an independent relationship between white matter abnormalities on MRI and cerebral blood flow velocities (BFVs) in older adults with type 2 diabetes. (diabetesjournals.org)
  • 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. (nih.gov)
  • Regadenoson (400-500 microg) increased heart rate by up to 21 +/- 6 beats/min and decreased systolic blood pressure (-5 +/- 8 mm Hg to -24 +/- 16 mm Hg) and diastolic blood pressure (-8 +/- 4 mm Hg to -15 +/- 14 mm Hg). (biomedsearch.com)
  • Note also in Figure 12.13 that blood pressure fluctuates in the arterial system between systolic blood pressure and diastolic blood pressure. (lubopitko-bg.com)