Blood Flow Velocity: A value equal to the total volume flow divided by the cross-sectional area of the vascular bed.Regional Blood Flow: The flow of BLOOD through or around an organ or region of the body.Ultrasonography, Doppler, Transcranial: 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.Cerebrovascular Circulation: The circulation of blood through the BLOOD VESSELS of the BRAIN.Middle Cerebral Artery: 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, Doppler: 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)Ophthalmic Artery: Artery originating from the internal carotid artery and distributing to the eye, orbit and adjacent facial structures.Cerebral Arteries: The arterial blood vessels supplying the CEREBRUM.Pulsatile Flow: Rhythmic, intermittent propagation of a fluid through a BLOOD VESSEL or piping system, in contrast to constant, smooth propagation, which produces laminar flow.Ultrasonography, Doppler, Color: 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, Doppler, Pulsed: 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.Coronary Circulation: The circulation of blood through the CORONARY VESSELS of the HEART.Blood Pressure: PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.Vascular Resistance: 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.Laser-Doppler Flowmetry: 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.Hemodynamics: The movement and the forces involved in the movement of the blood through the CARDIOVASCULAR SYSTEM.Hypocapnia: Clinical manifestation consisting of a deficiency of carbon dioxide in arterial blood.Ciliary Arteries: Three groups of arteries found in the eye which supply the iris, pupil, sclera, conjunctiva, and the muscles of the iris.Retinal Artery: 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.Echocardiography, Doppler: 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.Echoencephalography: Use of reflected ultrasound in the diagnosis of intracranial pathologic processes.Rheology: 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.Umbilical Arteries: 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.Hyperventilation: 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.Microcirculation: The circulation of the BLOOD through the MICROVASCULAR NETWORK.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Diastole: Post-systolic relaxation of the HEART, especially the HEART VENTRICLES.Ultrasonography, Prenatal: 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.Anterior Cerebral Artery: 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.Hyperemia: 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).Heart Rate: The number of times the HEART VENTRICLES contract per unit of time, usually per minute.Ultrasonography: 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.Models, Cardiovascular: 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.Arteries: The vessels carrying blood away from the heart.Reference Values: 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.Intracranial Pressure: Pressure within the cranial cavity. It is influenced by brain mass, the circulatory system, CSF dynamics, and skull rigidity.Systole: Period of contraction of the HEART, especially of the HEART VENTRICLES.Heart Rate, Fetal: The heart rate of the FETUS. The normal range at term is between 120 and 160 beats per minute.Celiac Artery: The arterial trunk that arises from the abdominal aorta and after a short course divides into the left gastric, common hepatic and splenic arteries.Coronary Vessels: The veins and arteries of the HEART.Homeostasis: The processes whereby the internal environment of an organism tends to remain balanced and stable.Vasodilation: The physiological widening of BLOOD VESSELS by relaxing the underlying VASCULAR SMOOTH MUSCLE.Acetazolamide: 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)Gestational Age: 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.Vasodilator Agents: Drugs used to cause dilation of the blood vessels.Dogs: 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)Doppler Effect: 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.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Oxygen: 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.Mesenteric Artery, Superior: 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.Fetal Growth Retardation: The failure of a FETUS to attain its expected FETAL GROWTH at any GESTATIONAL AGE.Brain: 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.Circle of Willis: 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, Doppler, Color: Echocardiography applying the Doppler effect, with the superposition of flow information as colors on a gray scale in a real-time image.Carotid Artery, Internal: Branch of the common carotid artery which supplies the anterior part of the brain, the eye and its appendages, the forehead and nose.Placental Circulation: The circulation of BLOOD, of both the mother and the FETUS, through the PLACENTA.Prospective Studies: 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.Collateral Circulation: Maintenance of blood flow to an organ despite obstruction of a principal vessel. Blood flow is maintained through small vessels.Reproducibility of Results: 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.Hemorheology: The deformation and flow behavior of BLOOD and its elements i.e., PLASMA; ERYTHROCYTES; WHITE BLOOD CELLS; and BLOOD PLATELETS.Tilt-Table Test: 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)Fetal Heart: 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.Posterior Cerebral Artery: 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.Vasomotor System: The neural systems which act on VASCULAR SMOOTH MUSCLE to control blood vessel diameter. The major neural control is through the sympathetic nervous system.Hypotension, Orthostatic: 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.Echocardiography: Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic.Splanchnic Circulation: The circulation of blood through the BLOOD VESSELS supplying the abdominal VISCERA.Hypercapnia: A clinical manifestation of abnormal increase in the amount of carbon dioxide in arterial blood.Flow Cytometry: 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.Blood Viscosity: 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.Pulmonary Circulation: The circulation of the BLOOD through the LUNGS.Blood Circulation Time: 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.Posture: The position or attitude of the body.Blood Volume: Volume of circulating BLOOD. It is the sum of the PLASMA VOLUME and ERYTHROCYTE VOLUME.Partial Pressure: 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)Papaverine: 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.Retinal Vessels: The blood vessels which supply and drain the RETINA.Uterus: 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.Echocardiography, Transesophageal: Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues using a transducer placed in the esophagus.Vasoconstriction: The physiological narrowing of BLOOD VESSELS by contraction of the VASCULAR SMOOTH MUSCLE.Echocardiography, Doppler, Pulsed: 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.Cardiac Output: 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).Adenosine: 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.Renal Circulation: The circulation of the BLOOD through the vessels of the KIDNEY.Carotid Arteries: 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.Oxygen Consumption: 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)Mitral Valve: The valve between the left atrium and left ventricle of the heart.Ventricular Function, Left: 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.Orthostatic Intolerance: 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)Infant, Newborn: An infant during the first month after birth.Microspheres: Small uniformly-sized spherical particles, of micrometer dimensions, frequently labeled with radioisotopes or various reagents acting as tags or markers.Fetus: 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.Infant, Premature: A human infant born before 37 weeks of GESTATION.Hematocrit: 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.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Blood Circulation: The movement of the BLOOD as it is pumped through the CARDIOVASCULAR SYSTEM.Sensitivity and Specificity: 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)Ductus Arteriosus: A fetal blood vessel connecting the pulmonary artery with the descending aorta.Xenon Radioisotopes: 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.Plethysmography: Recording of change in the size of a part as modified by the circulation in it.Veins: The vessels carrying blood away from the capillary beds.Ultrasonography, Doppler, Duplex: 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.Coronary Angiography: Radiography of the vascular system of the heart muscle after injection of a contrast medium.Observer Variation: 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).Arterial Occlusive Diseases: 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.Pulse: 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.Atrial Function, Left: The hemodynamic and electrophysiological action of the LEFT ATRIUM.Carotid Artery, Common: 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.Predictive Value of Tests: 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.Rest: Freedom from activity.Basilar Artery: 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.Cerebrovascular Disorders: 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.Supine Position: The posture of an individual lying face up.Liver Circulation: The circulation of BLOOD through the LIVER.Magnetic Resonance Angiography: 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.Lower Body Negative Pressure: 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.Coronary Disease: 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.Pia Mater: 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.Dipyridamole: 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)Retinal Vein: 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.Renal Artery: A branch of the abdominal aorta which supplies the kidneys, adrenal glands and ureters.Valsalva Maneuver: Forced expiratory effort against a closed GLOTTIS.Nitroglycerin: A volatile vasodilator which relieves ANGINA PECTORIS by stimulating GUANYLATE CYCLASE and lowering cytosolic calcium. It is also sometimes used for TOCOLYSIS and explosives.Eye: 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.Carotid Stenosis: 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)Cerebrospinal Fluid Pressure: Manometric pressure of the CEREBROSPINAL FLUID as measured by lumbar, cerebroventricular, or cisternal puncture. Within the cranial cavity it is called INTRACRANIAL PRESSURE.Fetal Diseases: Pathophysiological conditions of the FETUS in the UTERUS. Some fetal diseases may be treated with FETAL THERAPIES.Photoplethysmography: 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.Femoral Artery: The main artery of the thigh, a continuation of the external iliac artery.Ultrasonography, Interventional: 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.Hypotension: 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.Cerebral Arterial Diseases: 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.Mephentermine: 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.Heart: The hollow, muscular organ that maintains the circulation of the blood.Stress, Mechanical: 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.Anoxia: Relatively complete absence of oxygen in one or more tissues.Fourier Analysis: 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)Vertebral Artery: The first branch of the SUBCLAVIAN ARTERY with distribution to muscles of the NECK; VERTEBRAE; SPINAL CORD; CEREBELLUM; and interior of the CEREBRUM.Cardiac Catheterization: Procedures in which placement of CARDIAC CATHETERS is performed for therapeutic or diagnostic procedures.Tomography, Emission-Computed, Single-Photon: 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.Myocardial Contraction: Contractile activity of the MYOCARDIUM.Ethamsylate: Benzenesulfonate derivative used as a systemic hemostatic.Constriction, Pathologic: The condition of an anatomical structure's being constricted beyond normal dimensions.Respiration: 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).Pulmonary Artery: The short wide vessel arising from the conus arteriosus of the right ventricle and conveying unaerated blood to the lungs.Pregnancy Trimester, Second: The middle third of a human PREGNANCY, from the beginning of the 15th through the 28th completed week (99 to 196 days) of gestation.Blood Gas Analysis: Measurement of oxygen and carbon dioxide in the blood.Stroke Volume: 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, Inhalation: Anesthesia caused by the breathing of anesthetic gases or vapors or by insufflating anesthetic gases or vapors into the respiratory tract.Ultrasonics: 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.Regression Analysis: 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.Cerebral Veins: Veins draining the cerebrum.Brain Ischemia: 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.Capillaries: The minute vessels that connect the arterioles and venules.Xenon: 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, Emission-Computed: Tomography using radioactive emissions from injected RADIONUCLIDES and computer ALGORITHMS to reconstruct an image.Subarachnoid Hemorrhage: 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.Nitric Oxide: 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.Isoflurane: A stable, non-explosive inhalation anesthetic, relatively free from significant side effects.Intracranial Hypertension: 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.Head-Down Tilt: Posture while lying with the head lower than the rest of the body. Extended time in this position is associated with temporary physiologic disturbances.Healthy Volunteers: 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)Altitude: A vertical distance measured from a known level on the surface of a planet or other celestial body.Leg: The inferior part of the lower extremity between the KNEE and the ANKLE.Vasospasm, Intracranial: 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).Nitroprusside: 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.Ephedrine: 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.Monitoring, Intraoperative: The constant checking on the state or condition of a patient during the course of a surgical operation (e.g., checking of vital signs).Contrast Media: Substances used to allow enhanced visualization of tissues.Brachial Artery: The continuation of the axillary artery; it branches into the radial and ulnar arteries.Vena Cava, Inferior: The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs.Magnetic Resonance Imaging: 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.Aging: The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.Spectroscopy, Near-Infrared: 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.Intraocular Pressure: The pressure of the fluids in the eye.Endarterectomy, Carotid: The excision of the thickened, atheromatous tunica intima of a carotid artery.Syncope, Vasovagal: Loss of consciousness due to a reduction in blood pressure that is associated with an increase in vagal tone and peripheral vasodilation.Postoperative Period: The period following a surgical operation.Oximetry: 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.Hydrodynamics: The motion of fluids, especially noncompressible liquids, under the influence of internal and external forces.Follow-Up Studies: 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.Endothelium, Vascular: Single pavement layer of cells which line the luminal surface of the entire vascular system and regulate the transport of macromolecules and blood components.Nitrous Oxide: 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.Tricuspid Valve: The valve consisting of three cusps situated between the right atrium and right ventricle of the heart.Coronary Stenosis: Narrowing or constriction of a coronary artery.Dilatation, Pathologic: The condition of an anatomical structure's being dilated beyond normal dimensions.Feasibility Studies: Studies to determine the advantages or disadvantages, practicability, or capability of accomplishing a projected plan, study, or project.Monitoring, Physiologic: 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.Aorta: The main trunk of the systemic arteries.Hypertension: 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.Linear Models: 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.Autonomic Nerve Block: 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.Carbonic Anhydrase Inhibitors: A class of compounds that reduces the secretion of H+ ions by the proximal kidney tubule through inhibition of CARBONIC ANHYDRASES.Sympathetic Nervous System: 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.Angioplasty, Balloon, Coronary: Dilation of an occluded coronary artery (or arteries) by means of a balloon catheter to restore myocardial blood supply.Muscle, Skeletal: 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.Cross-Over Studies: 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, Intravenous: Injections made into a vein for therapeutic or experimental purposes.Pulmonary Veins: The veins that return the oxygenated blood from the lungs to the left atrium of the heart.Cerebral Angiography: Radiography of the vascular system of the brain after injection of a contrast medium.

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)

*Rhaponticum

Expands peripheral blood vessels and increases blood flow velocity. - Displays the lactic acid from the muscle. - Improves ...

*Motion (physics)

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 ... EQUATIONS OF UNIFORM MOTION: If v = final velocity, u = initial velocity, a = acceleration, t = time, s = displacement, then : ... "Flow velocity of single lymphatic capillaries in human skin". Am J Physiol Heart Circ Physiol. 270 (1): H358-H363. PMID 8769772 ... However, the velocities of plates range widely. The fastest-moving plates are the oceanic plates, with the Cocos Plate ...

*Myocardial perfusion imaging

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 ...

*Face perception

Droste DW, Harders AG, Rastogi E; Harders; Rastogi (August 1989). "A transcranial Doppler study of blood flow velocity in the ... CS1 maint: Multiple names: authors list (link) Njemanze PC (September 2004). "Asymmetry in cerebral blood flow velocity with ... "Brain activity and blood flow velocity changes: a transcranial Doppler study". Int. J. Neurosci. 47 (1-2): 91-102. doi:10.3109/ ... derived from Fourier analysis of mean blood flow velocity to trigger target face search from a computerized face database ...

*Acoustocerebrography

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 ...

*Transcranial Doppler

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 ...

*Napoleon Cybulski

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 ...

*Visual impairment due to intracranial pressure

"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 ...

*Compression stockings

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 ... ECS occurs on long flights, due to traveler's inactivity, gravity, and cramped seating, and slows down the blood flow through ... Compression stockings are recommended under the following conditions: Tired, aching legs occur when the blood flow slows down ...

*Migraine treatment

... relationship to cerebral blood flow velocity in the middle cerebral artery". Headache. 43 (3): 245-50. doi:10.1046/j.1526- ... "Effect of biofeedback-assisted relaxation on migraine headache and changes in cerebral blood flow velocity in the middle ... with which one can hear the blood flowing through the vessel. Use of the three-dimensional CT scan and the Doppler Flowmeter ... In contrast to aspirin, it is not a blood thinner (and thus may be used in patients where coagulation is a concern), and it ...

*Medical ultrasound

... produce accurate assessment of the direction of blood flow and the velocity of blood and cardiac tissue at any arbitrary point ... A blood flow study is done prior to the injection, by power doppler. The blood flow can be destroyed and the node become ... which measure the velocity of blood flow through the brain's blood vessels transcranially (through the cranium). They are used ... Doppler mode: This mode makes use of the Doppler effect in measuring and visualizing blood flow Color Doppler: Velocity ...

*Mitral valve stenosis

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 ...

*Infant crying

Increased blood pressure will have an effect on cerebral blood flow, cerebral blood flow velocity and intracranial pressure. ... Increased pressures and velocity can lead to intracranial hemmorrhage. Prolonged exhalation may also cause some adverse effects ... The cortisol levels will rise along with blood pressure. ...

*Arteriole

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 ...

*Bruit

Anything increasing the blood flow velocity such as fever, anemia, or hyperthyroidism, can increase the amplitude of the bruit ... Bruit (English: /ˈbruːi/; from French, "noise"), or vascular murmur, is the abnormal sound generated by turbulent flow of blood ... or a localized high rate of blood flow through an unobstructed artery. The bruit may be heard ("auscultated") by pressing a ... stethoscope to the skin over the turbulent flow and listening. Most bruits occur only in systole, so the bruit is intermittent ...

*Karl von Vierordt

He is credited with the construction of an early "hemotachometer", an apparatus for monitoring the velocity of blood flow. In ... Vierordt developed techniques and tools for the monitoring of blood circulation. ... 1854, he created a device called a sphygmograph, a mechanism consisting of weights and levers used to estimate blood pressure, ...

*Christian J. Lambertsen

"Relationship of 133Xe cerebral blood flow to middle cerebral arterial flow velocity in men at rest". J. Cereb. Blood Flow Metab ... Lambertsen CJ (August 1998). "Invited editorial on "Fast and slow components of cerebral blood flow response to step decreases ... "Observations on the volume of blood flow and oxygen utilization of the carotid body in the cat". J. Physiol. 125 (1): 67-89. ... "Some observations on the carotid body blood flow in the cat". Am. J. Med. Sci. 226 (2): 230. PMID 13065304. CS1 maint: Uses ...

*Subarachnoid hemorrhage

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 ...

*Discovery and development of phosphodiesterase 5 inhibitors

The capillary blood flow velocity also increased in each individual patient and the mean capillary flow velocity of all ... Sildenafil has been shown to significantly improve neurovascular coupling without affecting overall cerebral blood flow by ... These results came without significant reductions of the systemic blood pressure. Sildenafil has shown promise in the treatment ...

*Liver support systems

Schmidt, LE; Svendsen, LB; Sørensen, VR; Hansen, BA; Larsen, FS (August 2001). "Cerebral blood flow velocity increases during a ... In the last 22 patients, cerebral perfusion pressure was monitored by Doppler (mean flow velocity in middle cerebral artery), ... The blood circuit uses a double lumen catheter and a conventional hemodialysis device to pump the patient's blood into the MARS ... Blood is dialysed against a human serum albumin (HSA) dialysate solution that allows blood detoxification of both water-soluble ...

*VisualSonics

Thus, the Doppler function was only suitable for imaging low velocity blood flow in veins, small arteries, arterioles, or in ... Image acquisition was improved to 30 frames per second, enabling imaging of fast events such as heartbeats and blood flow in ... Software quantification packages such as Power Doppler provided researchers with flexibility in studying blood flow and other ... In addition, Advanced Cardiovascular Functionality provides Tissue Doppler Imaging (TDI), Integrated Blood Pressure Measurement ...

*Sleep inertia

Levels of cerebral blood flow (CBF) and cerebral blood flow velocities (CBFV) will take up to 30 minutes to increase and reach ... Studies using advanced imaging have shown that cerebral blood flow will return to waking levels in the brainstem and thalamus ... Then, after 15 minutes, the brain's anterior cortical regions receive normal daytime blood flow. This 15 minute time period ... and a feeling of tiredness will result Studies show that individuals express a lack of blood flow to the brain upon awakening. ...

*Taurine

... can influence (and possibly reverse) defects in nerve blood flow, motor nerve conduction velocity, and nerve sensory ... Journal of Cerebral Blood Flow and Metabolism. 15 (5): 852-9. doi:10.1038/jcbfm.1995.106. PMID 7673378. Leon R, Wu H, Jin Y, ... Taurine crosses the blood-brain barrier and has been implicated in a wide array of physiological phenomena including inhibitory ... El Idrissi A, Okeke E, Yan X, Sidime F, Neuwirth LS (2013). "Taurine regulation of blood pressure and vasoactivity". Adv. Exp. ...

*Julie Makani

"Risk factors for high cerebral blood flow velocity and death in Kenyan children with Sickle Cell Anaemia: role of haemoglobin ... In sickle cell disease, red blood cells are abnormally shaped, causing problems with the flow of blood through the body and the ... Blood. 117 (4): 1390-1392. doi:10.1182/blood-2010-08-302703. PMID 21068433. Retrieved 20 March 2014. "Sickle Cell Foundation of ... From 2014 she is Wellcome Trust Research Fellow and Associate Professor in the Department of Haematology and Blood Transfusion ...

*Kosmos 1667

A similar correlative study was performed during the Cosmos 1514 mission, where blood flow velocity was compared to total body ... The main objective of American participation in the Kosmos 1667 mission was to measure carotid artery pressure and blood flow ... Instrument calibration procedures were modified on this mission to ensure that blood pressure measurements would be accurate. ...

*Reduced muscle mass, strength and performance in space

McDonald, KS; Delp, MD; Fitts, RH (June 1992). "Effect of hindlimb unweighting on tissue blood flow in the rat". Journal of ... Maximal shortening velocities were increased by 14% and 24% in the 6-day and 14-day spaceflight groups, respectively. These ... Lee, SM; Williams, WJ; Schneider, SM (May 2002). "Role of skin blood flow and sweating rate in exercise thermoregulation after ... McDonald, KS; Delp, MD; Fitts, RH (September 1992). "Fatigability and blood flow in the rat gastrocnemius-plantaris-soleus ...
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.. ...
Maintaining a constant cerebral blood flow during a change in cerebral perfusion pressure is known as autoregulation. The integrity of this phenomenon is considered to be important in preventing cerebral lesions in preterm infants. A study was carried out using Doppler ultrasound measurements of cerebral blood flow velocities (CBFV) as an indicator of alterations in cerebral haemodynamics. CBFV were recorded on a beat to beat basis over 60 second epochs, during which time the cerebral perfusion pressure was changed by rapidly altering the infants posture from horizontal to either 20 degrees head up or head down. An informative response in CBFV was considered to be either (a) a uniphasic, immediate, passive alteration in velocity occurring with the change in posture and without a subsequent change or (b) a biphasic response of an initial change in CBFV followed within 20 seconds by a second response. This latter response is considered to be consistent with autoregulatory activity. A total of 501 ...
1. Peak blood flow acceleration measured in the common carotid artery was compared with peak flow acceleration measured in the ascending aorta of three baboons.. 2. The response to occlusion for 60 s of the circumflex branch or the anterior descending branch of the left coronary artery was investigated.. 3. Both accelerations decreased approximately to the same extent. Peak aortic flow velocity, stroke volume and cardiac output also decreased but to a smaller extent.. 4. It is concluded that peak aortic flow acceleration is a sensitive index of myocardial function during acute coronary occlusion in conscious primates and that peak carotid flow acceleration is an indirect measure of myocardial performance under the same conditions.. ...
Purpose: : Fundus imaging is essential for diagnosing and monitoring common ophthalmic and systemic diseases. The Retinal Function Imager (RFI) is a non-invasive, easy to use, direct qualitative and quantitative imaging method that extends the utility of fundus imaging by providing quantitative information about retinal blood flow velocity. It can also be used for blood oximetry, capillary bed topography, and examining the metabolic state of the retina. Here we concentrated on characterizing blood flow velocity in retinal arteries and veins and accomplishing a nearly two-fold reduction of the variance of blood-flow velocity measurements by coupling the measurement to the heartbeat-cycle. Methods: : One eye of each of 14 healthy volunteers (mean age 30.7 years) was tested. Each subject had at least two separate sessions of imaging using the RFI. Results: : The mean velocity in non-heartbeat synchronized subjects was 6.1± 2.4 mm/sec for secondary and tertiary macular artery segments, and 4.4 ± ...
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
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. ...
A dependence on the position of the vessel relative to the location of the placenta was seen. Significant differences were noted when all subgroups were compared (Fig. 17). 1Sl). 27 L-.. 001 n = 71 n = 69 fZB- ~ Internal placental border External placental border ® 0 n = 27 Distant from placenta o Fig. 17. 2 Reproducibility The means and the relative coefficient of variation for the 67% and 90% confidence limits for fetal and uteroplacental blood flow parameters are presented in Table 9. Parameters with a low coefficient of variation show little dispersion about the mean and are most readily reproducible. The median value decreased from 290 ml/kg per minute in pregnancy week 24/0 to 220 mljkg in pregnancy week 40/0 (Fig. 39). - Ratio of mean blood flow volume of fetal common carotid artery to estimated fetal weight showed a decreasing trend until pregnancy week 38/0, followed by a slight increase. The median value changed from 60 ml/kg per minute in pregnancy week 28/0 to 46 ml/kg in ...
Figure 1 presents an en face plane from an age related macular degeneration (AMD) patient. It shows the removal of bias for flow estimation (grayscale is normalized to the highest flow). a) was processed with the method of direct calculation and b) with the MAP estimator. The backstitched scan pattern can be seen in the bias due to gradual changes in the background noise caused by revisitation error (i.e. the error in rescanning the same location). This induced an offset in method a) but the MAP estimator could isolate the flow from it. Figure 2 shows quantitative flow in the same en face plane processed with the MAP estimator to provide flow velocities. The determined flow velocities are within the expected range for retinal capillaries of 0.2 to 3.3 mm/s.. ...
Blood flow measurement using an improved surface integration of velocity vectors (SIVV) technique was tested in in vitro phantoms. SIVV was compared with true flow (12-116 mL/s) in a steady-state model using two angles of insonation (45 degrees and 60 degrees ) and two vessel sizes (internal diameter = 11 and 19 mm). Repeatability of the method was tested at various flow rates for each angle of insonation and vessel. In a univentricular pulsatile model, SIVV flow measured at the mitral inlet was compared to true flow (29-61 mL/s). Correlation was excellent for the 19-mm vessel (r(2)= 0.99). There was a systematic bias but close limits of agreement (mean +/- 2 SD = -24.1% +/- 7.6% at 45 degrees; +16.4% +/- 11.0% at 60 degrees ). Using the 11-mm vessel, a quadratic relationship was demonstrated between between SIVV and true flow (r(2) = 0.98-0.99), regardless of the angle of insonation. In the pulsatile system, good agreement and correlation were shown (r(2) = 0.94, mean +/- 2 SD = -4.7 +/- ...
Neurosurgery. 2010 Sep;67(3 Suppl Operative):ons102-7; discussion ons107. doi: 10.1227/01.NEU.0000383152.50183.81. Clinical Trial
Dynamic cerebral autoregulation (DCA) capacity along with the degree of internal carotid artery (ICA) stenosis and characteristics of the plaque can also play an important role in selection of appropriate treatment strategy. This study aims to classify the patients with severe ICA stenosis according to preoperative state of DCA and to assess its dynamics after surgery. Thirty-five patients with severe ICA stenosis having different clinical type of disease underwent reconstructive surgery. DCA was assessed with transfer function analysis (TFA) by calculating phase shift (PS) between Mayer waves of blood flow velocity (BFV) and blood pressure (BP) before and after operation ...
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 ...
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 ...
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 ...
An epicardial multifunctional probe has been designed to measure blood flow velocity and muscle thickening with two sensors. The probe is implantable and remains inside the patient after surgery. The probe is removable through a small opening in the patients chest.
Correlation between aortic velocity time integral (AoVTI) at Adaptive CRT and echo-optimized device settings (AoVTI is an echocardiographic representative of stroke volume and cardiac performance ...
Level of Blood Flow  The normal blood flow to the brain is about 50 mL/100g of brain tissue/min.  Ischemic penumbra is a blood flow of 25 mL/100g of brain tissue/min. This level is dangerously low and can lead to loss of brain cells.  A blood flow of 8 mL/100g of brain tissue/min leads to an almost complete loss of functional neurons.  Consciousness is lost within 10 seconds of cessation of blood supply to the brain. Dr. Michael P. Gillespie 3
Color flow mapping has become an important clinical tool, for diagnosing a wide range of vascular diseases. Only the velocity component along the ultrasonic beam is estimated, so to find the actual blood velocity, the beam to flow angle has to be known. Because of the unpredictable nature of vascular hemodynamics, the flow angle cannot easily be found as the angle is temporally and spatially variant. Additionally the precision of traditional methods is severely lowered for high flow angles, and they breakdown for a purely transverse flow. To overcome these problems we propose a new method for estimating the transverse velocity component. The method measures the transverse velocity component by estimating the transit time of the blood between two parallel lines beamformed in receive. The method has been investigated using simulations performed with Field II. Using 15 emissions per estimate, a standard deviation of 1.64% and a bias of 1.13% are obtained for a beam to flow angle of 90 degrees. ...
For example, doctors usually determine whether the heart is pumping enough blood through the primary arteries to end organs by taking an ultrasound measurement called Velocity Time Integral (VTI). Hardware with AI-enabled features, such as Venue and Venue Go, developed by GE Healthcare, can get that VTI reading in seconds, not minutes. Thats because once physicians have an image of the patients beating heart, they can tap a button on the screen (Auto VTI) and the system will automatically place a box where the organs left ventricle meets the aorta, the bodys main artery. (The sample box looks similar to the frame that pops up over peoples faces when you take a photo on a smartphone.). Algorithms do the rest. Within seconds, they can analyze the outlined waveform showing the readings for the rate of blood flow in meters per second, and its volume in liters per minute. The technology dramatically reduces the number of keystrokes and the time it would take to calculate the flow rate manually. ...
How to Treat Shock. Shock is a life-threatening medical emergency caused by interruption of the normal blood flow, which cuts off the supply of oxygen and nutrients to cells and organs. Immediate emergency medical treatment is required....
Pitching velocity secrets from the pros. There are actually many of posts on the internet titled something similar to this article, most of them are useless, given that they focus primarily on upper body mechanics as the only methods to developing velocity. Any hard thrower will show you, there is a lot more to velocity…
This apparatus allow the study of different methods of flow measurement in an incompressible fluid. This a direct application of the steady flow energy equation ; Bernoullis theorem.
Doppler Measurements & Calculations: MV E max vel: 83 cm/sec, MV A max vel: 86 cm/sec, MV E/A:0.96, MV dec time: 0.24 sec, Ao V2 max: 136cm/sec, Ao max PG: 7.0mmHg, LV max PG:3.0mmHg, LV V1 max:90 cm/sec, TR max vel: 204 cm/sec, TR max PG:17 mmHg,RVSPC(TR):22mmHg, RAP systole:5.0 ...
However, that all may be about to change. Blogger and macro specialist Naufal Sanaullah made an interesting observation recently: the United States economy looks like it is finally escaping its liquidity trap, thanks in large part to the stabilization in U.S. housing prices. Sanaullahs basic argument can be summed up in his thesis (emphasis added): Although deleveragings and liquidity traps are inextricably linked, sufficient income growth and credit velocity can allow for the economy to leave the liquidity trap, even as it continues to deleverage (through the denominators impact). This allows for a virtuous cycle to return, as traditional monetary policy regains efficacy and feeds into aggregate demand growth.. In other words, although the economy still has more to delever (reduce debt levels relative to GDP), the deleveraging process may now be helped along by monetary policy, instead of the two forces continuing to work in opposition to each other. To really understand what is going on ...
Our aim is to keep you doing what you do best. And we know that things happen. If you arent 100% satisfied with any product youve received from us, we want to know about it. Check out our warranty policy. ...
At TechnosAmigos.com we go through detailed Qiku N4S vs ZTE Axon 7 Comparison in terms of device specifications, features & price.
Coronary flow velocity reserve (CFVR) measured by transthoracic Doppler echocardiography of the LAD is used to assess microvascular function but validation studies in clinical settings are lacking. We aimed to assess feasibility, reproducibility and agreement with myocardial flow reserve (MFR) measured by PET in overweight and obese patients. Participants with revascularized coronary artery disease were examined by CFVR. Subgroups were examined by repeated CFVR (reproducibility) or Rubidium-82-PET (agreement). To account for time variation, results were computed for scans performed within a week (1-week) and for all scans regardless of time gap (total) and to account for scar tissue for patients with and without previous myocardial infarction (MI). Eighty-six patients with median BMI 30.9 (IQR 29.4-32.9) kg × m−2 and CFVR 2.29 (1.90-2.63) were included. CFVR was feasible in 83 (97 %) using a contrast agent in 14 %. For reproducibility overall (n = 21) limits of agreement (LOA) were (−0.75;0.71),
Previous reports have indicated that hypertensive patients who have angina-like chest pain and normal coronary arteriograms have reduced coronary flow velocity reserve (CFVR) levels. In addition, elevated plasma endothelin-1 (ET-1) levels have been reported to be associated with microvascular angina. The purpose of this study was to evaluate the plasma ET-1 levels and CFVR in patients with chest pain but without coronary artery disease (CAD). A total of 66 patients were included in this study. CAD was ruled out by exercise stress test or coronary angiogram. Plasma ET-1 and CFVR measurements were performed in patients with (n=35) and without (n=31) a history of angina-like chest pain. CFVR was measured using adenosine-triphosphate stress transthoracic Doppler echocardiography. The mean ET-1 level was significantly higher and the CFVR was significantly lower in patients in the symptomatic group than in those in the asymptomatic group (ET-1: 3.85±1.24 pg/ml vs. 2.98±1.27 pg/ml, CFVR: 2.26±0.48 vs. 2.77
KP Hanretty, MJ Whittle, PC Rubin; Influence of Atenolol on Human Umbilical and Uteroplacental Doppler Flow Velocity Waveforms. Clin Sci (Lond) 1 January 1988; 74 (s18): 64P. doi: https://doi.org/10.1042/cs074064Pa. Download citation file:. ...
We investigated the effect of acute hypoxia (AH) on dynamic cerebral autoregulation (CA) using two independent assessment techniques to clarify previous, conflicting reports. Twelve healthy volunteers (6 men, 6 women) performed six classic leg cuff tests, three breathing normoxic (Fi(O2) = 0.21) and three breathing hypoxic (Fi(O2) = 0.12) gas, using a single blinded, Latin squares design with 5-min washout between trials. Continuous measurements of middle cerebral artery blood flow velocity (CBFv; DWL MultiDop X2) and radial artery blood pressure (ABP; Colin 7000) were recorded in the supine position during a single experimental session. Autoregulation index (ARI) scores were calculated using the model of Tiecks et al. (Tiecks FP, Lam AM, Aaslid R, Newell DW. Stroke 26: 1014-1019, 1995) from ABP and CBFv changes following rapid cuff deflation (cuff ARI) and from ABP to CBFv transfer function, impulse, and step responses (TFA ARI) obtained during a 4-min period prior to cuff inflation. A new ...
Recently, short-term visual deprivation has been shown to affect a variety of non-visual processes and regional cortical activity (Sathian & Zangaladze, 2001). Surprisingly, very little is known about how such visual deprivation impacts regional cerebral blood flow velocity (CBFv) or its adaptation with the underlying neuronal activity (i.e., neurovascular coupling). The current study sought to investigate the effects of short-term (two-hour) visual deprivation on regional CBFv and neurovascular coupling. CBFv (transcranial Doppler ultrasound) was measured concurrently in the posterior cerebral artery (PCA) and the middle cerebral artery (MCA). Neurovascular coupling was assessed using established methods, consisting of two minutes of baseline (eyes closed and reading), five cycles of 40 seconds reading - 20 seconds eyes-closed (primary protocol), and five cycles of 40 seconds eyes-moving - 20 seconds eyes-closed (secondary protocol). Neurovascular coupling, using both protocols, was collected ...
Fifteen patients (median age 8.5 years) with fixed right ventricular outflow tract obstruction were evaluated by two-dimensional echocardiographically directed continuous wave Doppler ultrasound within 24 hours of cardiac catheterization. Pulmonary artery blood velocity measurements were determined from a real time spectral display of pulmonary artery flow profile and converted to pressure drop utilizing a modified Bernoulli equation. Use of both parasternal and subcostal imaging permitted more accurate detection of maximal flow velocity than did use of either approach alone. Gradients estimated from Doppler recordings correlated well with those measured at cardiac catheterization (correlation coefficient= 0.95, standard error of the estimate = 7.9 mm Hg) with a trend to slight underestimation of gradient in more severe obstruction. In three patients with combined valvular and subvalvular stenosis and one patient with right ventricular outlet obstruction due totally to a ventricular septal ...
The 102 fetuses diagnosed by ultrasound to be asymmetrically growth-retarded had blood flow velocity waveforms of the umbilical artery studied. Sixty-two cases had normal blood flow, 28 had abnormal blood flow but with present end-diastolic flow, 8 had absent end-diastolic flow, and 4 had reversal of end-diastolic flow. Comparison was made between the blood flow status and other biophysical methods of antenatal surveillance and perinatal outcome. There is a strong correlation between abnormal blood flow and abnormalities detected by other biophysical methods of antenatal surveillance. Our study shows that fetuses with severe blood flow impairment tend to be more severely growth-retarded and to be delivered earlier. Our results also show abnormal blood flow to be associated with a poor perinatal outcome. Those fetuses with severe impairment of blood flow suffered a high incidence of operative delivery for fetal distress, acidosis at birth, perinatal mortality and morbidity. The association ...
TY - JOUR. T1 - The assessment of skin blood flow in peripheral vascular disease by laser Doppler velocimetry. AU - Karanfilian, R. G.. AU - Lynch, T. G.. AU - Lee, B. C.. AU - Long, J. B.. AU - Hobson, R. W.. PY - 1984/12/1. Y1 - 1984/12/1. N2 - The helium-neon laser Doppler (LD) is designed to measure skin blood flow velocity (SBFV). Flow velocity and pulse wave amplitude are expressed in millivolts (mv) relative to a zero-flow reference. The authors have reviewed their initial experience in ten persons (20 limbs) without peripheral vascular disease (PVD, group I) and nine patients (12 limbs) with severe PVD (group II). The finger, palm, great toe, and forehead had a significantly (P , 0.05) greater flow velocity than the plantar and dorsal foot, distal and proximal leg, thigh, chest, arm, and forearm. Baseline and hyperemic SBFV, measured at the great toe, were compared in groups I and II. In group I, the baseline SBFV (mv, mean ± standard error of the mean (SEM) in the great toe was 197 ± ...
Myocardial perfusion imaging (MPI), using single photon emission computed tomography (SPECT) is a validated method for detecting coronary artery disease. Transthoracic Doppler echocardiography (TTDE) of flow at rest and during adenosine provocation has previously been evaluated in selected patient groups. We therefore wanted to compare the diagnostic ability of TTDE in the left anterior descending coronary artery (LAD) to that of MPI in an unselected population of patients with chest pain referred for MPI. Our hypothesis was that TTDE with high accuracy would identify healthy individuals and exclude them from the need for further studies, enabling invasive investigations to be reserved for patients with a high probability of disease. Sixty-nine patients, 44 men and 25 women, age 61 ± 10 years (range 35-82), with a clinical suspicion of stress induced myocardial ischemia, were investigated. TTDE was performed at rest and during adenosine stress for myocardial scintigraphy. We found that coronary flow
article{2286a0f7-5934-41f8-aed8-94b7a8b75a40, abstract = {Recent studies indicate a severely reduced coronary flow reserve (CFR) in neonates with congenital heart disease. The significance of these studies remains debatable, as the ability of the anatomically normal neonatal heart to increase coronary flow is currently unknown. This study was designed to establish normal values for CFR in newborns after administration of adenosine [pharmacologic CFR (pCFR)] and as induced by acute hypoxemia (reactive CFR). Thirteen mechanically ventilated newborn lambs were studied. Coronary flow velocities were measured in the proximal left anterior descending coronary artery before and after adenosine injection (140 and 280 mug/kg i.v.) using an intracoronary 0.014-in Doppler flow-wire. Measurements were made at normal oxygen saturation (Sao(2)) and during progressive hypoxemia induced by lowering the fraction of inspired oxygen. CFR was defined as the ratio of hyperemic to basal average peak flow velocity. In ...
Authors: Kashif FM, Verghese GC, Novak V, Czosnyka M, Heldt T.. Intracranial pressure (ICP) is affected in many neurological conditions. Clinical measurement of pressure on the brain currently requires placing a probe in the cerebrospinal fluid compartment, the brain tissue, or other intracranial space. This invasiveness limits the measurement to critically ill patients. Because ICP is also clinically important in conditions ranging from brain tumors and hydrocephalus to concussions, noninvasive determination of ICP would be desirable. Our model-based approach to continuous estimation and tracking of ICP uses routinely obtainable time-synchronized, noninvasive (or minimally invasive) measurements of peripheral arterial blood pressure and blood flow velocity in the middle cerebral artery (MCA), both at intra-heartbeat resolution. A physiological model of cerebrovascular dynamics provides mathematical constraints that relate the measured waveforms to ICP. Our algorithm produces patient-specific ...
Doppler ultrasound of female reproductive system is a method for evaluating uterine arteries blood flow. Together with the measurement of the endometrium thickness, Ultrasongraphy becomes an important way of assessing risk of myomas, bleeding and endometrial cancer in menopausal ladies. Uterus measurements (width,length and depth),endometrial thickness, Doppler measurement of uterine arteries indices (Peak Systolic Velocity, Time Average Maximum Velocity, Pulsatility Index) were taken in 50 menopausal ladies. The study was carried out in UAE AbuDhabi Samha and Shahama clinics during the period from June 2014 to june 2015 2012. The endometrial thickness, uterine arteries pulstility index , resistance index, Peak Systolic Velocity and Time Average Maximum Velocity,uterus echogenicity were correlated significantly with the mean of average age and posmenpausal age In age of 62 yrs and postmenopausal age of 50 yrs, doppler examination of L&R uterine arteries showed its blood flow velocity waveform ...
To evaluate the haemodynamic changes induced by flow diversion treatment in cerebral aneurysms, resulting in thrombosis or persisting aneurysm patency over time. Eight patients with aneurysms at the para-ophthalmic segment of the internal carotid artery were treated by flow diversion only. The clinical follow-up ranged between 6 days and 12 months. Computational fluid dynamics (CFD) analysis of pre- and post-treatment conditions was performed in all cases. True geometric models of the flow diverter were created and placed over the neck of the aneurysms by using a virtual stent-deployment technique, and the device was simulated as a true physical barrier. Pre- and post-treatment haemodynamics were compared, including mean and maximal velocities, wall-shear stress (WSS) and intra-aneurysmal flow patterns. The CFD study results were then correlated to angiographic follow-up studies. Mean intra-aneurysmal flow velocities and WSS were significantly reduced in all aneurysms. Changes in flow patterns were
To evaluate the accuracy of a pulsed multigated Doppler system, 128 carotid arteries were examined. The spectral broadening index was calculated from the power spectrum of a small sample volume located in the center of the stream according to the flow profile and was related to the degree of stenosis as determined by contrast angiography. Even minor wall irregularities seen on the angiogram were classified as disease. The ability of the system to discriminate between normal and diseased vessels reached a sensitivity of 94% and a specificity of 91%. Classification of greater than 50% or less than 50% stenosis could be performed with a sensitivity of 90% and a specificity of 85%. Pulsed multigated Doppler ultrasonography allows identification of even minor degrees of stenosis of the carotid artery and provides an alternative to duplex scanning. Furthermore, the blood flow profile provided by a multigated Doppler system may add valuable information concerning blood flow characteristics not ...
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This paper analyzes velocity profiles for flow through circular tubes in laminar, turbulent, and transition region flows and how they affect measurement by flow-meters. Experimental measurements of velocity profiles across the cross-section of straight circular tubes were made using laser doppler velocimetry. In addition, flow visualization was done using the hydrogen bubble technique. Velocity profiles in the laminar and the turbulent flow are quite predictable which allow the determination of meter factors for accurate flow measurement. However, the profiles can not be predicted at all in the transition region. Therefore, for the accuracy of the flowmeter, it must be ensured that the flow is completely in the laminar regime or completely in the turbulent regime. In the laminar flow a bend, even at a large distance, affects the meter factor. The paper also discusses some strategies to restructure the flow to avoid the transition region.. ...
Aliasing is associated only with pulsed Doppler, it never appears with continuous wave Doppler. A standard continuous wave Doppler has a receiver and a transmitter. The transmitter produces continuous sound waves which the receiver collects. Both elements are positioned at specific angles from one another enabling the receiver to receive reflected ultrasound waves.. The disadvantage of using a continuous wave Doppler is the range ambiguity. With this technique, velocities along the entire region of overlap between the transmit and receive beams, blend together to form the spectrum. With pulsed Doppler, velocities from blood within the sample volume are measured.. Eliminating aliasing "improves the ability to measure the maximum velocity with Doppler".. ...
Biomech Model Mechanobiol. 2013 Jan 1. [Epub ahead of print] Leinan PR, Degroote J, Kiserud T, Skallerud B, Vierendeels J, Hellevik LR. Source Biomechanics Division, Department of Structural Engineering, The Norwegian University of Science and Technology, 7491, Trondheim, Norway, [email protected] Abstract The veins distributing oxygenated blood from the placenta to the fetal body have been given much attention in clinical Doppler velocimetry studies, in particular the ductus venosus. The ductus venosus is embedded in the left liver lobe and connects the intra-abdominal portion of the umbilical vein (IUV) directly to the inferior vena cava, such that oxygenated blood can bypass the liver and flow directly to the fetal heart. In the current work, we have developed a mathematical model to assist the clinical assessment of volumetric flow rate at the inlet of the ductus venosus. With a robust estimate of the velocity profile shape coefficient (VC), the volumetric flow rate may be estimated as ...
We thank Miller et al. for their interest in the results of our assessment of noninvasive ICP measurement technology. This method is accurate and sensitivity and specificity are much higher compared with other approaches.1,6,7. Blood flow in both segments of the OA depends on ICP, ambulatory blood pressure, heart rate, intraocular pressure, intraorbital pressure, and other factors.1 The benefit of our method is in the equilibration of ICP with Pe. The balance ICP = Pe is not dependent on influential factors. OA blood flow velocities could be very different in different patients1 but the balance ICP = Pe does not depend on the OA blood flow velocity values. As a result, our method does not need a patient-specific calibration. All "correlation-based" noninvasive ICP measurement approaches cannot be used for absolute ICP value measurements because they need patient-specific calibration, which is impossible.. Our 2-depth transcranial Doppler technology complies with all safety standards. The maximum ...
This study is the first to use the constant routine (CR) protocol to determine whether the endogenous circadian pacemaker contributes to the previously reported diurnal changes in CBFV. The current work demonstrates that, with limited periodic external stimuli and a constant posture, there is 24-hour rhythmicity in CBFV. Subjects showed a cycle of approximately 24 hours in CBT, which has been previously demonstrated with the CR [21].. Figure 3 illustrates the intricate relationship between the rhythms across the study period. At approximately the CBT acrophase, the relationship between the two rhythms undergoes a transition. Between 180 and 240 degrees, CBFV is still rising and CBT is changing directions (first rising, reaching its peak and then falling). This period between 180 and 240 has been described as a "wake maintenance zone", a time in the circadian cycle during which humans are less likely to fall asleep [22]. In our subjects, the CBT is near its zenith or just starting to fall at this ...
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Quantification of blood velocity data obtained usingultrasound may be used in clinical diagnosis and inepidemiological studies of cardiovascular disease.
3D CINE Phase Contrast Magnetic Resonance Imaging (PCMRI) is considered the technique of election to study in vivo the time varying, complex blood flow structures evolving into arteries [1]. PCMRI allows to obtain a quantitative depiction of the spatial distribution of blood velocities from the acquired phase data and the anatomical image of the district of interest from magnitude data. A major limitation in the application of 3D CINE PCMRI to the clinical practice is the long scan time needed to obtain phase datasets (i.e., blood flow velocities) of sufficient quality for hemodynamic visualizations of time evolving fluid structures or for volumetric flow rates retrospective quantification and analysis. Recently, huge efforts have been done to speed up in vivo acquisitions by implementing/optimizing parallel imaging acquisition schemes as the Sensitivity Encoding (SENSE) [2]. However, the increased reduction factors employed in SENSE scheme to speed up the acquisition lead to acquired PCMRI ...
The authors have been developing a model of blood flow in the heart. The flow model of the heart enables us to estimate the entire blood flow of the heart from a couple of 2-D color Doppler images. Therefore, the load on patients is expected to be reduced. To develop the model of the heart, precise observation and an understanding of the blood flow are indispensable, because the flow is strongly related to the diagnosis of heart diseases. The visualization method must have the following features: (1) 3-D (2) objectivity (3) interactivity and (4) multi-aspect. The authors have developed visualization methods to meet the above-mentioned requirements and evaluated the proposed methods with the in-vitro flow data set. The results clearly reveal that the proposed system enables the researchers of the modeling group to obtain the state of entire flow, such as the occurrence of turbulence.. ...
Doppler optical coherence tomography has the capability to measure blood flow quantitatively and in vivo. As only the axial component of the velocity can be assessed, the measurements have to be corrected for the angle of the vessels. We present a novel approach to extract quantitative flow data from circumpapillary scans in vivo on the human retina by registering the circular scan to a reference volume scan and extracting the angle directly from the volume. In addition, we perform phase unwrapping and interpolation of the flow under the assumption of a parabolic flow profile. We demonstrate the repeatability of the methods by applying it to different retinal vessels, achieving coefficients of variation of the average velocity of 3 to 8%. Results on the pulsatility and resistance index are also presented.. ©2010 Optical Society of America. Full Article , PDF Article ...
To the Editor:. Michelson et al,1 from study of the ophthalmic artery flow pulse in the frequency domain, have noted features that are associated with aging and hypertension, and have the potential to identify early stages of microvascular disease in the eye. The findings concur with our studies of the carotid flow pulse in the time domain, which, likewise, are associated with aging and hypertension2 and have the potential to explain microvascular disease and "pulse wave encephalopathy" in the brain.3 The common link is early wave reflection from peripheral sites in the lower body, consequent on arterial stiffening; this increases amplitude of the lower harmonics of carotid arterial flow (and pressure) waves and in the time domain is apparent as increase in flow (and pressure) augmentation index.4 The explanation by Michelson et al1 relates to characteristics of the ophthalmic arterys vascular bed. We believe that this is unlikely, and note the evidence of similar and low-resistance index in ...
... Course is taught by leading vascular ultrasound experts and offers fifteen (15) months unlimited access to the online courses, plus two (2) days/16 hours scan lab with a 3:1 faculty to participant hands-on scan ratio at our facility in St. Petersburg, FL.
Nonuniform lateral scanning of the probe beam in optical coherence tomography produces imaging artifacts and leads to a morphologically inaccurate representation of the sample. Here, we demonstrate a solution to this problem, which is based on the Doppler shift carried by the complex-valued depth-resolved scattering amplitude. Furthermore, we demonstrate the feasibility of Doppler flow velocity measurements in underlying flow channels while laterally scanning the imaging probe over large surfaces with arbitrary and varying velocity. Finally, we performed centimeters-long hand-held B-mode imaging of skin in vivo.. ©2012 Optical Society of America. Full Article , PDF Article ...
Although crucial in regulating intracranial hydrodynamics, the cerebral venous system has been rarely studied because of its structural complexity and individual variations. The purpose of our study was to evaluate the organization of cerebral venous system in healthy adults. Phase-contrast magnetic resonance imaging (PC-MRI) was performed in 18 healthy volunteers, in the supine position. Venous, arterial, and cerebrospinal fluid (CSF) flows were calculated. We found heterogeneous individual venous flows and variable side dominance in paired veins and sinuses. In some participants, the accessory epidural drainage preponderated over the habitually dominant jugular outflow. The PC-MRI enabled measurements of venous flows in superior sagittal (SSS), SRS (straight), and TS (transverse) sinuses with excellent detection rates. Pulsatility index for both intracranial (SSS) and cervical (mainly jugular) levels showed a significant increase in pulsatile blood flow in jugular veins as compared with that ...
博士論文. Recently, quantitative flow visualization has become an important tool to investigate three-dimensional complex flow structures in microfluidic. The development of laser, computer and digital image processing techniques made it possible to extract velocity field information from visualized flow images of tracer particles. Particle image velocimetry (PIV) / particle tracking velocimetry (PTV) method has become one of the most useful flow diagnostic technologies in the modern history of fluid mechanics. The particle based velocimetry techniques measure the whole velocity field information in a plane by dividing that is placements Δx and Δy of tracer particles with the time interval Δt during which the particles were displaced. Since the flow velocity is inferred from the particle displacement, it is also important to select proper tracer particles that follow the flow motion accurately without changing the flow properties. These methods have been accepted as a reliable and ...
Hello, I have a question about the pressure and velocity change when merging two tubes that have the exact same pressure, velocity, and diameter. Ive attached an image to give you guys a visualization. Say the three tubes are all laying flat on the ground, so theres no height change ...
This test will take approximately 1 hour. A technician will place placing a transducer on your abdomen with a small amount of ultrasound gel. The transducer sends sound waves through your abdomen to the aorta and back. Then with the aid of computers software and a monitor we are able to image the aorta and display it on a monitor in front of you.. In conjunction with this imaging we will assess the blood flow with both pulsed Doppler and Color Flow Doppler, which measure the speed and direction of the blood flow. By assigning color to the direction of blood flow-called Color Flow Mapping-large areas of blood flow may be studied, which allows abnormal blood flow characteristics to be interpreted by the cardiologist.. After you leave the laboratory the technologist will document measurements from the images. A Baylor Scott & White Legacy Heart Center physician will review the images and measurements. If you have had a previous study the results will be compared.. ...
An echo Doppler is a medical test used to detect the size, shape, and motion of the heart. Doctors often order an echo Doppler if...
An image processing apparatus includes an identification unit configured to identify a retinal blood vessel based on a retinal image, a measurement unit configured to measure blood flow information for the blood vessel based on the retinal image, and a display control unit configured to display the measured blood flow information by at least one selected from a depth of the identified blood vessel, a size of the identified blood vessel, and a combination of both.
49. Two- and three-piece multicomponent prostheses in the penis. However, during coitus, especially with young (18 weeks) control rats. Androgen deficiency in aging men as persons who are on and then, despite his attenuated sexual excitement, potentially leading to fractures after minimal trauma. This may mean that they were ready to respond with arousal or penetration difficulties in both sexes. These changes, which may be part of her cardiovascular health, you should discuss this with an increase in mean peak systolic flow velocity or coronary artery disease. Further, an intense fear of pregnancy, the testicles dont produce enough testosterone, the group at this time also, the relationship between reduced ejaculation and patient-reported outcome measures (loss of self-esteem affecting relationship satisfaction and level of arousal, and pleasure without necessarily having orgasms or16 intercourse is defined in either core or peripheral nervous network described above, but supramaximal ...
One of the major criticisms of ultrasound Doppler is its angle dependency, that is its ability to measure velocity components directly to or from the transducer only. The present article aims to investigate the impact of this angular error in a clinical setting. Apical two- and four-chamber views were recorded in 43 individuals, and the myocardium was marked by hand in each image. We assume that the main direction of the myocardial velocities is longitudinal and correct for the angular error by backprojecting measured velocities onto the longitudinal direction drawn. Strain was calculated from both corrected and uncorrected velocities in 12 segments for each individual. The results indicate that the difference between strain values calculated from corrected and uncorrected velocities is insignificant in 5 segments and within a decimal range in 11 segments. The biggest difference between measured and corrected strain values was found in the apical segments. Strain is also found to be more robust ...
LVETc and PEPsu were automatically measured from electrocardiogram and finger photoplethismography. Atrioventricular (AV) and mode switch (CRT to DDD) were used as hemodynamic challenges. Performance of SI, beat-by-beat systolic blood pressure (SBP), and Doppler aortic velocity/time integral (AoVTI) were compared in 36 patients, and SIs detection of CRT to DDD mode switch in nine patients, responders to CRT. AVs were changed from 30 ms to 250 ms (20 ms steps) at constant paced heart rate, alternating with a reference AV (RefAV), to reduce hemodynamic drift. The coefficient of variation (standard deviation/mean) of SI, SBP, and AoVTI during all RefAVs were used as error marker. The percentage detection of hemodynamic changes during AV transitions was a marker of sensitivity. ...
이완기능 장애의 단계를 평가하는데 중요한 요소는 승모판 혈류속도(mitral flow velocities), 승모판륜 e 값, E/e 값, 최고 TR 속도 및 좌심방 최대 용적지수이다. 보조적으로 폐정맥 혈류속도와 좌심실 GLS 값이 이용될 수 있다. 가이드라인(ASE/EACVI guidelines 2016)에서 제시한 알고리즘은 평균 좌심방압을 평가하기 위해 지표들을 사용하였으며 심방세동, 유의한 승모판막 질환, 좌각차단, 심박동기의 사용 등을 배제한 상황에서 평가할 수 있다. 좌심실 박출률이 저하된 환자에서는 좌심방압이 상승되었는지 알아보기 위해 보통 승모판 유입혈류 패턴이 충분하고 E 속도의 감속시간(deceleration time, DT)이 예후의 중요한 예측 인자이지만, 좌심실 박출률이 보존된 환자에서는 2D 변수를 포함한 여러가지 지표들이 좌심방압을 평가하기 위해 필요할 수 있다.. 좌심실 박출률이 ...
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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. The image processor includes means for independently designating persistence factors for smoothing calculated speed and power of the dynamic portion of a field of view within a vasculature. Furthermore, the designation of a particular image point within a field of view as a dynamic image point (such as a blood flow region) as opposed to a static image point (such as a tissue region) is determined by averaging signal values for image points proximate to an image point of interest over both time and space.
An apparatus for measuring a propagation velocity of a pulse wave which is propagated through an artery of a living subject, the apparatus including an electrocardiographic-waveform detecting device which detects an electrocardiographic waveform from the subject, a pulse-wave sensor which is adapted to be worn on the subject and which detects the pulse wave from the subject, a time-difference determining device for determining a time difference between a first periodic point relating to the detected electrocardiographic waveform and a second periodic point relating to the detected pulse wave, and a propagation-velocity determining means for determining the propagation velocity of the pulse wave based on the determined time difference.
Hello, I need help with coding doppler flow wire in the femoral artery. I have been looking and just cannot find a code for this. I apprec
To discuss the clinical ultiliazation and significance of microembolus detection by transcranial Doppler (TCD) sonography in intracranial stenosis-occlusive disease. All related articles in this review were mainly searched from PubMed published in English from 1996 to 2012 using the terms of microe...
Circulatory System Blood Blood Flow In Human Circulatory System Stock Images Image 35501514 photo, Circulatory System Blood Blood Flow In Human Circulatory System Stock Images Image 35501514 image, Circulatory System Blood Blood Flow In Human Circulatory System Stock Images Image 35501514 gallery
Die Behandlung von Blut außerhalb und unabhängig von einem Patienten. The treatment of blood outside and independent of a patient. Hier hat man ähnlich wie beim 2. Anwendungsfall im wesentlichen konstante Blutströmungsmengen und konstante Blutströmungsgeschwindigkeiten. Here you have similar to the second application substantially constant blood flow rates and constant blood flow velocities. Zum ersten Anwendungsfall ist aus der US-A-3 785 380 eine Blutabsaugvorrichtung bekannt, welche aus einem zylindrischen Gehäuse, in welchem sich mikroporöses Filtermaterial zum Ausfiltern von Luftbläschen und anderen Verunreinigungen aus einem von einem Patienten abgesaugten Blutstrom befinden, einer Blutabsaugkanüle an einem vorderen Ende des Gehäuses und aus einer Blutabsaugleitung am hinteren Ende des Gehäuses besteht. For the first application, a blood-suction device is known from US-A-3,785,380, which consists of a cylindrical housing, are in which is micro-porous filter material for ...
Exercise and Increased Blood Flow - As you exercise, your body increases blood flow to your working muscles. See how your nervous system gets the blood flow to the right place.
Numerical simulations of pulsatile blood flow through a symmetrical branch modeling the aortic bifurcation were carried out to assess several hemodynamic theories of atherogenesis by comparing the distribution of hemodynamic variables with that of early lesions in arterial branches. Considerable spatial and temporal variations in wall shear were found when the flow was pulsatile; the highest values occurred at the convex corner on the outer wall of the branch and in the neighborhood of the flow divider tip, and the lowest shears were experienced by the outer wall of the daughter vessel a short distance distal to the corner. Transient flow reversal occurred almost everywhere in the branch, and a transient separated region was found corresponding to the low-shear region in the daughter vessel. The shear profiles and the calculated separated region were influenced to some degree by the extent of flow development at the branch inlet and markedly by the branch area ratio. All of the proposed ...
The flow waveform is the most interesting waveform. Much information can be derived from its shape. When flow is being used to generate a controlled level of pressure, the shape of the inspiratory flow waveform is informative regarding the necessary inspiratory time (if flow reaches zero, then the inspiratory time could be shorter without compromising volume). The expiratory flow pattern is also informative, as a slow return to baseline is an indication of the resistance to airflow.
tee junctions with sharp and round corners. Rounding the corners reduced the energy losses by between 10 and 20%, depending on the flow rate ratio, due to the reduction in the branching flow loss coefficient, whereas the straight flow basically remained unaffected. The corresponding detailed measurements of mean and turbulent velocities for a Reynolds number of 31,000 and flowrate ratio of 50% showed that rounding the corner lead to an increase in turbulence in the branch pipe. The increased turbulence diffused momentum more efficiently thus reducing the length of the recirculation by 25% with its width and strength also decreasing in magnitude. The overall effect of the increased dissipation due to turbulence and reduced dissipation due to mean flow irreversibilities in the recirculation was a decrease in the corresponding loss coefficient.. ...
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second) was identified as the highest velocity produced after the onset of velocity. Acceleration (in degree per second squared) was calculated as the linear slope of the velocity-time curve (Δvelocity/Δtime) from velocity onset to 2 deg/s below the PV attained. The onset of velocity was defined as 2 deg. ...
Restricting blood flow to brain - Causes of Head Numbness | LIVESTRONG.COM. Healthy blood flow is the key to Natural Male Enhancement. Decreased blood flow can be the result of smoking, poor diet, or even just getting older.
Blood flow after miscarriage - Not Sure if Pregnant - Facts about Miscarriage. Healthy blood flow is the key to Natural Male Enhancement. Decreased blood flow can be the result of smoking, poor diet, or even just getting older.
Phase-contrast MR can detect flow in the three cardinal directions along which bipolar encoding gradients are applied. This allows calculation of three velocity vector components: vx, vy, and vz. These components be displayed as separate images using using a gray scale to define direction (superior-to-inferior, left-to-right, or anterior-to-posterior). Alternatively, the velocities may be combined into a single magnitude image, where the intensity of each voxel is proportional to the speed (S) given by ...
A number of methods for ultrasound vector velocity imaging are presented in the paper. The transverse oscillation (TO) method can estimate the velocity transverse to the ultrasound beam by introducing a lateral oscillation in the received ultrasound field. The approach has been thoroughly investigated using both simulations, flow rig measurements, and in-vivo validation against MR scans. The TO method obtains a relative accuracy of 10% for a fully transverse flow in both simulations and flow rig experiments. In-vivo studies performed on 11 healthy volunteers comparing the TO method with magnetic resonance phase contrast angiography (MRA) revealed a correlation between the stroke volume estimated by TO and MRA of 0.91 (p,;0.01) with an equation for the line of regression given as: MRA = 1.1 · TO-0.4 ml. 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). A ...
From question on page 763 A repeat Doppler duplex ultrasound was performed which revealed a filiform circumscript stenosis at the site of the portal vein anastomosis, leading to blood flow acceleration up to 100 cm/s (fig 1A). A computed tomography scan confirmed the stenosis in the ...
Raynauds is a rare disorder that affects blood flow in the arteries. People who have Raynauds may have normal blood flow some of the time, but occasional episodes where the blood vessels narrow and restrict flow. These episodes are known as vasospasms, and they affect the fingers, toes or other parts of the body.
JUAN CARLOS DEL ALAMO, PH. D.. Intracardiac Blood Flow Quantification in the Clinical Setting. Ready for Prime Time?. Recent advances in imaging technology and computational fluid dynamics now allow physicians to obtain non-invasive robust measurements of intracardiac blood flow in the clinical setting. These advances have revealed that blood flow inside the heart chambers is characterized by the formation of unsteady vortex structures, generated during filling, that eventually last until the chambers are emptied.. This talk will summarize our recent efforts toward understanding how these flow patterns contribute to the function of the left ventricle (the main pumping chamber of the heart). We will show that the normal ventricular flow patterns: 1) Contribute to efficient filling of the ventricle. 2) Efficiently redirect the transit of blood towards the ventricles outflow tract. 3) Minimize the number of cardiac cycles that blood stays in ventricular transit, thereby reducing the risk of ...
3. Does output force or velocity alone characterize lever mechanics?. Levers exhibit a force-velocity trade-off because they transmit power (equation (1.4)). In McHenrys analysis, the springs input power is not the same in each simulation. This is because the rate of energy release from the spring depends on the inertial resistance of the mass (which depends on lout). By accelerating the same mass with the same length-dependent (but not rate-dependent) force, McHenry guarantees that his higher A lever transmits greater power (figure 2 and electronic supplementary material, figure S1). Though arguably interesting, this approach makes it difficult to infer general principles about the effects of lever geometry-especially if only the output force and velocity are considered. To accurately characterize the mechanics of a lever, ratios of both the input and output forces and velocities must be analysed (equations (1.2)-(1.4)). Although maximum velocity may be relevant for McHenrys example, the ...
Edmonds-Karp come to the rescue with an insight that controls the order in which Ford-Fulkerson explores paths.. Notice that in the example above, if the shortest paths (by number of edges, not considering weight) are considered first, then the anomaly does not occur. We would find augmenting path 〈(A,B), (B,D)〉 to increase flow by 1000, then finish the job with augmenting path 〈(A,C), (C,D)〉, or find the second and then the first.. Edmonds-Karp is the Ford-Fulkerson algorithm but with the constraint that augmenting paths are computed by Breadth-First Search of Gf. ( I told you that those search algorithms are widely useful!). A proof in the CLRS text shows that the number of flow augmentations performed by Edmunds-Karp is O(VE). Since each BFS is still O(E) in a connected graph, Edunds-Karp runs in O(V E2) time. (This is O(V3) in sparse graphs and O(V5)in dense graphs.) The proof in CLRS works by bounding distances to vertices in Gf. Even better bounds are possible: this has been a very ...
Peak ascending and descending aortic blood flow velocities were measured using continuous wave Doppler ultrasound velocimetry in 30 children with coarctation or recoarctation of the aorta and in 13 control subjects. The results were compared with the arm to leg systolic blood pressure difference. The peak flow velocities in the descending aorta were significantly higher in the patients than in the control subjects and there was a close correlation with the systolic blood pressure gradient. Since there was no overlap of flow velocities between the patients and the control subjects the Doppler technique enables coarctation confidently to be excluded as well as demonstrating its presence and severity. The method is simple, rapid, independent of the condition of the aortic valve, and is applicable to neonates in whom the diagnosis of coarctation may otherwise be difficult. In older children it is useful for detecting recoarctation and following its progress, particularly in patients in whom a ...
The study was aimed to establish normal Doppler blood flow parameters of right common carotid artery and right external jugular vein in 20 clinically healthy non-gravid adult buffaloes. The Doppler blood flow parameters were also studied in ten buffaloes suffering from reticulo-diaphragmatic hernia and the changes in the various blood flow parameters were compared with that of healthy buffaloes. The correlations among various blood flow parameters like the pulsatility index, resistive index, peak systole velocity, end diastole velocity, time average maximum velocity, time averaged mean velocity and volume flow for each vessel and between the vessels were worked out in healthy buffaloes. These parameters, when compared with those recorded in buffaloes suffering from reticulo-diaphragmatic hernia, revealed a significant decrease in peak systole velocity, end diastole velocity, time average maximum velocity and time averaged mean velocity of external jugular vein while the common carotid artery ...
Proximal Isovelocity Surface Area (PISA) method is based on the continuity equation. When a flow passes through a narrow orifice, as it approaches the narrowest region, there is a flow convergence and flow acceleration. PISA is the surface area of the hemisphere at the aliasing region of the flow convergence. PISA increases as the flow increases and also with lower aliasing velocity. To reduce errors in measurement, smaller aliasing velocity has to be set, to get higher PISA measurement with lower chance for errors.. Regurgitant flow rate can be calculated as:. 2 Pi r2 x Valiasing. Radius is measured from the orifice to point of colour change. If the flow convergence is not a true hemisphere, the angle subtended by the flow convergence at the orifice has to be measured and divided by 180 to get a correction factor. Good correlation between angiographic estimates of regurgitant flow and PISA based estimates have been reported.. ...
Editor,-Studies on visual field and peripheral circulation had led to the hypothesis that the eye might be involved in the vasospastic syndrome,1 a potential contributor to glaucomatous optic neuropathy.2 In some patients with peripheral vasospasms, visual field defects worsened after cold provocation, and, often, both peripheral vasospasms and visual field defects improved after calcium channel blocker treatment.1Because these and newer observations3 suggest some parallels in ocular and digital blood flow regulation, the relation between ophthalmic artery and nailfold capillary blood flow velocities was evaluated.. Fifty patients with primary open angle glaucoma with a mean age of 67 (SD 15) years were examined. Excluded were patients with previous filtering surgery or systemic and cardiovascular diseases. 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.4 The velocities ...
TY - JOUR. T1 - Reduction in cerebral blood flow volume in infants complicated with hypoxic ischemic encephalopathy resulting in cerebral palsy. AU - Fukuda, Sumio. AU - Mizuno, Keisuke. AU - Kawai, Satomi. AU - Kakita, Hiroki. AU - Goto, Tatenobu. AU - Hussein, Mohamed Hamed. AU - Daoud, Ghada A.. AU - Ito, Tetsuya. AU - Kato, Ineko. AU - Suzuki, Satoshi. AU - Togari, Hajime. PY - 2008/4/1. Y1 - 2008/4/1. N2 - Hypoxic ischemic brain can result in cerebral palsy, mental retardation, and learning disabilities in surviving children. The purpose of this study was to elucidate the cerebral blood flow volume in infants complicated with brain damage after the birth. Nine term infants with hypoxic ischemic encephalopathy and 41 normal term infants were studied. Four infants with HIE suffered from CP or mental retardation, and the other five infants exhibited normal neurodevelopment. The mean blood flow velocity and diameter of the internal carotid artery and the vertebral artery were measured for 28 ...
TY - JOUR. T1 - Visual function, optic nerve structure, and ocular blood flow parameters after 1 year of glaucoma treatment ith fixed combinations. AU - Januleviciene, Ingrida. AU - Ehrlich, Rita. AU - Siesky, Brent. AU - Nedzelskiené, Irena. AU - Harris, Alon. PY - 2009. Y1 - 2009. N2 - Purpose. To compare the effects of latanoprost/timolol (LTFC) versus dorzolamide/timolol (DTFC) fixed combinations on intraocular pressure (IOP), visual function, and retrobulbar blood flow in patients with open-angle glaucoma (OAG). Methods. This was a prospective, randomized, double masked, parallel study on 30 patients with OAG. All patients received 4 weeks of timolol treatment prior to randomization to LTFC or DTFC treatment. Measurements after randomization were taken at 1, 6, and 12 months, including arterial blood pressure; IOP; color Doppler imaging of the ophthalmic artery (OA), central retinal artery, and short posterior ciliary artery (SPCA); scanning laser polarimetry; Humphrey visual field ...
TY - JOUR. T1 - Clinical determinants of elevated systolic pulmonary artery pressure measured by transthoracic Doppler echocardiography in early systemic sclerosis. AU - EUSTAR co-authors. AU - Carreira, Patricia E.. AU - Carmona, Loreto. AU - Joven, Beatriz E.. AU - Loza, Estibaliz. AU - Andreu, José Luis. AU - Riemekasten, Gabriela. AU - Vettori, Serena. AU - Allanore, Yannick. AU - Balbir-Gurman, Alexandra. AU - Airò, Paolo. AU - Walker, Ulrich A.. AU - Damjanov, Nemanja. AU - Ananieva, Lidia P.. AU - Rednic, Simona. AU - Czirják, L.. AU - Distler, Oliver. AU - Farge, Dominique. AU - Hesselstrand, Roger. AU - Corrado, Ada. AU - Caramaschi, Paola. AU - Tikly, Mohammed. AU - Matucci-Cerinic, Marco. PY - 2017/1/1. Y1 - 2017/1/1. N2 - Objective. To explore the prevalence and clinical associations of elevated systolic pulmonary artery pressure (sPAP), measured by Transthoracic Dopplerechocardiography (TTE) in patients with early systemic sclerosis (SSc). Methods. A cross-sectional analysis of ...
1.2.1 Methods of modeling documents using the light of improved Koizumis method [1] Preparation of MCAO animal model. The external carotid artery ligation in rats, since the common carotid artery bifurcation to the carotid artery into plug-. line (18.5 ? 0.5) mm, block the middle cerebral artery blood flow, resulting in focal cerebral ischemia. After the tail of the plug wire placed through the skin, ischemia and 2 h after the bolt of light pulling lines caused by blood reperfusion. Survival in rats observed after 6,12,24 h reperfusion in rats changes in behavior. Zea Longa behavioral ratings refer to the five-point scale score criteria: ? 0 points: normal, no symptoms of nerve injury; ? 1 pm: contralateral forepaw flexion or full flexion part; ? 2 points: the hemiplegic side turning in circles; ? 3 points: the hemiplegic side of dumping; ? 4 points: You can not spontaneously walk, loss of consciousness. Sham-operated group, in addition to non-insertion lines, the remaining steps ibid. 1.2.2 ...

PHOTOPLETHYSMOGRAPHY: THE BLOOD VESSEL STATE AS A BASIS FOR THE HEALTH - Медсканер ВелнессPHOTOPLETHYSMOGRAPHY: THE BLOOD VESSEL STATE AS A BASIS FOR THE HEALTH - Медсканер Велнесс

... preventing adequate blood flow. Blood clots can be life-threatening, for example, if a pulmonary (lung) embolism occur. ... The pulse wave velocity through vessels depends on lumen width, vessel wall elasticity, thickness of the vessel wall and the ... The sensor is placed on the finger because of intensive capillary blood flow in the fingertip area. ... This is particularly important when there is an increased tendency for excessive blood clotting. Blood clots most frequently ...
more infohttp://bioscaner.com/en/tech/photoplethysmography-the-blood-vessel-state-as-a-basis-for-the-health/

Predictors and outcomes of shunt-dependent hydrocephalus in patients with aneurysmal sub-arachnoid hemorrhage | BMC Surgery |...Predictors and outcomes of shunt-dependent hydrocephalus in patients with aneurysmal sub-arachnoid hemorrhage | BMC Surgery |...

... of focal neurologic signs or deterioration in conscious state and evidence of vasospasm or presence of stenotic flow velocity ... Some studies show that the amount of blood in the sub-arachnoid space has special significance [5, 7] while the current study ... Re-bleeding was defined as sudden deterioration of the clinical state accompanied by new or increased blood on brain CT scan [9 ... Some authors suggest that the presence of blood clots and high CSF viscosity can lead to an obstructive form of hydrocephalus ...
more infohttps://bmcsurg.biomedcentral.com/articles/10.1186/1471-2482-12-12

Search Results for blood flow velocity | jnsSearch Results for "blood flow velocity" | jns

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 ...
more infohttps://thejns.org/search?q=%22blood%20flow%20velocity%22

Hemorrhage, Phenobarbital, and Fluctuating Cerebral Blood Flow Velocity in the Neonate | Articles | PediatricsHemorrhage, Phenobarbital, and Fluctuating Cerebral Blood Flow Velocity in the Neonate | Articles | Pediatrics

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 ...
more infohttp://pediatrics.aappublications.org/content/82/4/548..info

Altered cerebral blood flow velocity features in fibromyalgia patients in resting-state conditionsAltered cerebral blood flow velocity features in fibromyalgia patients in resting-state conditions

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. ...
more infohttp://journals.plos.org/plosone/article?id=10.1371/journal.pone.0180253

Carotid Velocities Determine Cerebral Blood Flow Deficits in Elderly Men with Carotid Stenosis |50%Carotid Velocities Determine Cerebral Blood Flow Deficits in Elderly Men with Carotid Stenosis |50%

Carotid Velocities Determine Cerebral Blood Flow Deficits in Elderly Men with Carotid Stenosis ,50%. Arkadiusz Siennicki-Lantz, ... C. H. Bai, J. R. Chen, H. C. Chiu, and W. H. Pan, "Lower blood flow velocity, higher resistance index, and larger diameter of ... Table 2: Correlation coefficients between peak systolic velocity in right/left ICA and cerebral blood flow estimated in several ... Table 3: Partial correlation coefficients between peak systolic velocity in right/left ICA and cerebral blood flow, controlled ...
more infohttps://www.hindawi.com/journals/ijvm/2012/579531/

Laboratory and Genetic Biomarkers Associated with Cerebral Blood Flow Velocity in Hemoglobin SC DiseaseLaboratory and Genetic Biomarkers Associated with Cerebral Blood Flow Velocity in Hemoglobin SC Disease

... 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, ...
more infohttps://www.hindawi.com/journals/dm/2017/6359871/ref/

Cerebral Blood Flow Velocity and Periventricular White Matter Hyperintensities in Type 2 Diabetes | Diabetes CareCerebral Blood Flow Velocity and Periventricular White Matter Hyperintensities in Type 2 Diabetes | Diabetes Care

... 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 ...
more infohttp://care.diabetesjournals.org/content/29/7/1529

Recent advances in blood flow vector velocity imaging - DTU OrbitRecent advances in blood flow vector velocity imaging - DTU Orbit

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- ...
more infohttp://orbit.dtu.dk/en/publications/recent-advances-in-blood-flow-vector-velocity-imaging

Brachial artery hyperemic blood flow velocities are related to carotid atherosclerosisBrachial artery hyperemic blood flow velocities are related to carotid atherosclerosis

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- ...
more infohttp://uu.diva-portal.org/smash/record.jsf?pid=diva2:317246

Dynamic Regulation of Middle Cerebral Artery Blood Flow Velocity in Aging and Hypertension | StrokeDynamic Regulation of Middle Cerebral Artery Blood Flow Velocity in Aging and Hypertension | Stroke

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 ...
more infohttp://stroke.ahajournals.org/content/31/8/1897

Neonatal cerebral blood flow velocity responses to changes in posture. | Archives of Disease in ChildhoodNeonatal cerebral blood flow velocity responses to changes in posture. | Archives of Disease in Childhood

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 ...
more infohttp://adc.bmj.com/content/69/3_Spec_No/304

The utility of using the bispectral index-Vista for detecting cross-clamping decline in cerebral blood flow velocity.  - PubMed...The utility of using the bispectral index-Vista for detecting cross-clamping decline in cerebral blood flow velocity. - PubMed...

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 ( ...
more infohttps://www.ncbi.nlm.nih.gov/pubmed/20679941

Quantification of pulmonary and systemic blood flow by magnetic resonance velocity mapping in the assessment of atrial-level...Quantification of pulmonary and systemic blood flow by magnetic resonance velocity mapping in the assessment of atrial-level...

... 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 ...
more infohttps://link.springer.com/article/10.1007%2FBF01806217

Blood flow velocity in the uterine and ovarian arteries during the normal menstrual cycleBlood flow velocity in the uterine and ovarian arteries during the normal menstrual cycle

... Sladkevicius, Povilas LU ; Valentin ... Doppler ultrasound, blood flow velocity, menstrual cycle. in Ultrasound in Obstetrics & Gynecology. volume. 3. issue. 3. pages ... blood flow velocity,menstrual cycle}, language = {eng}, number = {3}, pages = {199--208}, publisher = {John Wiley & Sons}, ... series = {Ultrasound in Obstetrics & Gynecology}, title = {Blood flow velocity in the uterine and ovarian arteries during the ...
more infohttps://lup.lub.lu.se/search/publication/1107482

Regadenoson, a selective A2A adenosine receptor agonist, causes dose-dependent increases in coronary blood flow velocity in...Regadenoson, a selective A2A adenosine receptor agonist, causes dose-dependent increases in coronary blood flow velocity in...

... 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. ...
more infohttp://www.biomedsearch.com/nih/Regadenoson-selective-A2A-adenosine-receptor/17679059.html

Relation between blood flow velocities in the ophthalmic artery and in nailfold capillaries | British Journal of OphthalmologyRelation between blood flow velocities in the ophthalmic artery and in nailfold capillaries | British Journal of Ophthalmology

The results suggest a relation between nailfold capillary blood cell velocity and blood flow velocity in the ophthalmic artery ... The relatively constant blood flow during the diastole might predict more closely blood cell velocity in the capillary bed. ... However, RI is not a measure of velocity. PSV represents a unique event in arterial blood flow, and, possibly, capillary blood ... 4 The velocities measured in each visible vessel were averaged. Blood flow velocity in the ophthalmic arteries was assessed by ...
more infohttp://bjo.bmj.com/content/83/4/501.7

Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle. | Circulation ResearchPhasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle. | Circulation Research

Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle.. K Ashikawa, H Kanatsuka ... Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle. ... Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle. ... Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle. ...
more infohttp://circres.ahajournals.org/content/59/6/704

A velocity profile equation for blood flow in small arterioles and venules of small mammals in vivo and an evaluation based on...A velocity profile equation for blood flow in small arterioles and venules of small mammals in vivo and an evaluation based on...

... 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 ...
more infohttp://www.biomedsearch.com/nih/velocity-profile-equation-blood-flow/19996521.html

Changes in cerebral artery blood flow velocity after intermittent cerebrospinal fluid drainage. | Archives of Disease in...Changes in cerebral artery blood flow velocity after intermittent cerebrospinal fluid drainage. | Archives of Disease in...

Doppler ultrasound was used to measure blood flow velocity in the anterior cerebral artery of six premature infants with ... There was a significant increase in mean blood flow velocity after the drainage procedures (+5.6 cm/s, 95% confidence interval ... Changes in cerebral artery blood flow velocity after intermittent cerebrospinal fluid drainage. ... Changes in cerebral artery blood flow velocity after intermittent cerebrospinal fluid drainage. ...
more infohttp://adc.bmj.com/content/69/1_Spec_No/74

Contribution of von Willebrand Factor to Thrombus Formation on Neointima of Rabbit Stenotic Iliac Artery Under High Blood-Flow...Contribution of von Willebrand Factor to Thrombus Formation on Neointima of Rabbit Stenotic Iliac Artery Under High Blood-Flow...

... 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 ...
more infohttp://atvb.ahajournals.org/content/early/2003/05/15/01.ATV.0000077206.35631.B2

Functional assessment of coronary artery stenosis by Doppler derived absolute and relative coronary blood flow velocity reserve...Functional assessment of coronary artery stenosis by Doppler derived absolute and relative coronary blood flow velocity reserve...

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 ...
more infohttps://heart.bmj.com/content/82/4/509

Teaching Video NeuroImages: High blood flow velocity in the parent artery prior to basilar tip aneurysm rupture | NeurologyTeaching Video NeuroImages: High blood flow velocity in the parent artery prior to basilar tip aneurysm rupture | Neurology

4D-flow MRI can provide comprehensive hemodynamics with accurate blood flow and velocity.2 MMD-derived concentrated inflow jet ... demonstrates blood flow direction (arrow). Velocity diagram (E, F) demonstrates maximum velocity variation throughout cardiac ... Teaching Video NeuroImages: High blood flow velocity in the parent artery prior to basilar tip aneurysm rupture. Fei Peng, ... Teaching Video NeuroImages: High blood flow velocity in the parent artery prior to basilar tip aneurysm rupture ...
more infohttps://n.neurology.org/content/93/23/1018

Comparison of phasic blood flow velocity characteristics of arterial and venous coronary artery bypass conduits. - Semantic...Comparison of phasic blood flow velocity characteristics of arterial and venous coronary artery bypass conduits. - Semantic...

To quantitate coronary bypass conduit flow velocity, we examined the phasic blood flow velocity patterns by intravascular ... CONCLUSIONS Patterns of resting phasic blood flow, as well as mean velocity and total velocity integral, differ significantly ... METHODS AND RESULTS Spectral phasic blood flow velocity was measured using an intravascular Doppler-tipped angioplasty ... Mean flow velocities, total velocity integral, and calculated maximal shear rates were significantly higher in all segments of ...
more infohttps://www.semanticscholar.org/paper/Comparison-of-phasic-blood-flow-velocity-of-and-Bach-Kern/3add9f95309e8254fb0ce9ec949aa536b1347417
  • 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)
  • 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)
  • 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)
  • 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)
  • Evans blue dye has been injected to demonstrate the flow patterns. (thejns.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)
  • A velocity profile equation for blood flow in small arterioles and venules of small mammals in vivo and an evaluation based on literature data. (biomedsearch.com)
  • An empirical parametric equation with 2 bluntness parameters was introduced for describing the velocity profile of blood in the small arterioles and venules of small mammals, in vivo, with the basic approximations of the axisymmetric flow in cylindrical geometry, zero velocity at the wall and a blunter than parabolic flow profile. (biomedsearch.com)
  • 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)
  • 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)
  • Quantification of left-to-right atrial shunts with velocity-encoded cine nuclear magnetic resonance imaging. (springer.com)
  • The pulsatility index and the time-averaged maximum velocity were calculated. (lu.se)
  • In the uterine arteries the pulsatility index was highest on day + 2, after which it decreased successively to its lowest value, whereas the time-averaged maximum velocity reached its. (lu.se)
  • In the non-dominant ovary, neither the pulsatility index nor the time-averaged maximum velocity manifested any consistent changes during the cycle. (lu.se)
  • In the dominant ovary, the time-averaged maximum velocity increased and the pulsatility index decreased after follicular rupture, being significantly higher and lower, respectively, in the luteal than in the follicular phase. (lu.se)
  • 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)
  • To evaluate the haemodynamic changes induced by flow diversion treatment in cerebral aneurysms, resulting in thrombosis or persisting aneurysm patency over time. (epfl.ch)
  • Relative flow velocity and WSS reduction in and of itself may result in aneurysm thrombosis in the majority of cases. (epfl.ch)
  • 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)
  • 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)
  • Magnetic resonance velocity mapping: Clinical application of a new technique. (springer.com)
  • Blood flow velocity in retinal veins, analyzed by RFI, significantly correlates with the volume of central retina. (arvojournals.org)
  • Flow reductions under aneurysm-specific thresholds may, however, be the reason why some aneurysms remain completely or partially patent after flow diversion. (epfl.ch)
  • 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)
  • The approach has been thoroughly investigated using both simulations, flow rig measurements, and in-vivo validation against MR scans. (dtu.dk)
  • 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)
  • citation needed] In classical mechanics, accurate measurements and predictions of the state of objects can be calculated, such as location and velocity. (wikipedia.org)
  • OBJECTIVE To determine the relation between the relative and absolute coronary blood flow velocity reserve (CFVR) compared with the results of 99m Tc MIBI single photon emission computed tomography (SPECT). (bmj.com)