OBJECTIVE: To apply a new non-invasive method for quantification of in vivo wall shear stress (WSS) by magnetic resonance (MR) FAcE velocity mapping and measure WSS in the human abdominal aorta. DESIGN: Prospective, open study. MATERIAL: Six voluntee

TY - JOUR. T1 - Breath-hold MR measurements of blood flow velocity in internal mammary arteries and coronary artery bypass grafts. AU - Sakuma, Hajime. AU - Globits, Sebastian. AU - OSullivan, Margaret. AU - Shimakawa, Ann. AU - Bernstein, Matthew A. AU - Foo, Thomas K F. AU - Amidon, Thomas M.. AU - Takeda, Kan. AU - Nakagawa, Tsuyoshi. AU - Higgins, Charles B.. PY - 1996/1. Y1 - 1996/1. N2 - Breath-hold velocity-encoded cine MR (VENC-MR) imaging is a feasible method for measuring phasic blood flow velocity in small vessels that move during respiration. The purposes of the current study are to compare breathhold VENC-MR measurements of flow velocities in the internal mammary arteries (IMA) with nonbreath-hold measurements and to characterize the systolic and diastolic flow velocity curves in a cardiac cycle in native IMA and IMA grafts. Flow velocity in 30 native IMA and 8 IMA grafts were evaluated with a breath-hold VENC-MR sequence with K-space segmentation and view-sharing ...

Coronary flow velocity reserve (CFVR) measured by transthoracic Doppler echocardiography of the LAD is used to assess microvascular function but validation studies in clinical settings are lacking. We aimed to assess feasibility, reproducibility and agreement with myocardial flow reserve (MFR) measured by PET in overweight and obese patients. Participants with revascularized coronary artery disease were examined by CFVR. Subgroups were examined by repeated CFVR (reproducibility) or Rubidium-82-PET (agreement). To account for time variation, results were computed for scans performed within a week (1-week) and for all scans regardless of time gap (total) and to account for scar tissue for patients with and without previous myocardial infarction (MI). Eighty-six patients with median BMI 30.9 (IQR 29.4-32.9) kg × m−2 and CFVR 2.29 (1.90-2.63) were included. CFVR was feasible in 83 (97 %) using a contrast agent in 14 %. For reproducibility overall (n = 21) limits of agreement (LOA) were (−0.75;0.71),

Previous reports have indicated that hypertensive patients who have angina-like chest pain and normal coronary arteriograms have reduced coronary flow velocity reserve (CFVR) levels. In addition, elevated plasma endothelin-1 (ET-1) levels have been reported to be associated with microvascular angina. The purpose of this study was to evaluate the plasma ET-1 levels and CFVR in patients with chest pain but without coronary artery disease (CAD). A total of 66 patients were included in this study. CAD was ruled out by exercise stress test or coronary angiogram. Plasma ET-1 and CFVR measurements were performed in patients with (n=35) and without (n=31) a history of angina-like chest pain. CFVR was measured using adenosine-triphosphate stress transthoracic Doppler echocardiography. The mean ET-1 level was significantly higher and the CFVR was significantly lower in patients in the symptomatic group than in those in the asymptomatic group (ET-1: 3.85±1.24 pg/ml vs. 2.98±1.27 pg/ml, CFVR: 2.26±0.48 vs. 2.77

KP Hanretty, MJ Whittle, PC Rubin; Influence of Atenolol on Human Umbilical and Uteroplacental Doppler Flow Velocity Waveforms. Clin Sci (Lond) 1 January 1988; 74 (s18): 64P. doi: https://doi.org/10.1042/cs074064Pa. Download citation file:. ...

We investigated the effect of acute hypoxia (AH) on dynamic cerebral autoregulation (CA) using two independent assessment techniques to clarify previous, conflicting reports. Twelve healthy volunteers (6 men, 6 women) performed six classic leg cuff tests, three breathing normoxic (Fi(O2) = 0.21) and three breathing hypoxic (Fi(O2) = 0.12) gas, using a single blinded, Latin squares design with 5-min washout between trials. Continuous measurements of middle cerebral artery blood flow velocity (CBFv; DWL MultiDop X2) and radial artery blood pressure (ABP; Colin 7000) were recorded in the supine position during a single experimental session. Autoregulation index (ARI) scores were calculated using the model of Tiecks et al. (Tiecks FP, Lam AM, Aaslid R, Newell DW. Stroke 26: 1014-1019, 1995) from ABP and CBFv changes following rapid cuff deflation (cuff ARI) and from ABP to CBFv transfer function, impulse, and step responses (TFA ARI) obtained during a 4-min period prior to cuff inflation. A new ...

Recently, short-term visual deprivation has been shown to affect a variety of non-visual processes and regional cortical activity (Sathian & Zangaladze, 2001). Surprisingly, very little is known about how such visual deprivation impacts regional cerebral blood flow velocity (CBFv) or its adaptation with the underlying neuronal activity (i.e., neurovascular coupling). The current study sought to investigate the effects of short-term (two-hour) visual deprivation on regional CBFv and neurovascular coupling. CBFv (transcranial Doppler ultrasound) was measured concurrently in the posterior cerebral artery (PCA) and the middle cerebral artery (MCA). Neurovascular coupling was assessed using established methods, consisting of two minutes of baseline (eyes closed and reading), five cycles of 40 seconds reading - 20 seconds eyes-closed (primary protocol), and five cycles of 40 seconds eyes-moving - 20 seconds eyes-closed (secondary protocol). Neurovascular coupling, using both protocols, was collected ...

Cerebral Doppler measurements seem to be a future method to evaluate the degree of fetal hypoxemia. The aim of this study was (1) to elaborate standard curves for the different cerebral vessels in our own population, and (2) to describe the predictive value of Doppler measurements for intrauterine growth retardation (IUGR) and fetal acidosis. We recorded cerebral flow velocity waveforms from 71 normal pregnancies to establish standard curves for the following vessels: proximal middle cerebral artery, distal middle cerebral artery and posterior cerebral artery. Finally, we calculated the cerebroplacentar index (CPI) for each case. The predictive values from the different vessels were determined in 24 patients with IUGR and 17 cases with fetal acidosis. The poor sensitivity and the low positive predictive value of each cerebral vessel is probably explained by the rather long interval between the last Doppler assessment and delivery (22 +/- 23 days). Reducing the interval to less than 7 days, the distal

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 ...

Previous clinical studies showed that the coronary wedge pressure is increased in the presence of collateral vessels, presumably as a consequence of a reduced collateral vascular resistance, resulting in a reduction of signs of ischemia during brief coronary occlusion ([3, 4, 6]). Our current understanding of the collateral circulation is limited, partly due to the lack of methods capable of expressing the development of the collateral vascular bed in terms of flow and resistance. The dynamic behavior of collateral vessels as seen angiographically before and during balloon coronary occlusion can be examined by blood flow velocity analysis in the contralateral donor coronary artery ([6, 7]). These studies demonstrated that a balloon coronary occlusion results in a transient 10% to 70% increase in coronary blood flow velocity in the contralateral artery when collateral vessels are present, although this phenomenon is marked in the absence of collateral vessels. Blood flow velocity changes in the ...

Authors: Kashif FM, Verghese GC, Novak V, Czosnyka M, Heldt T.. Intracranial pressure (ICP) is affected in many neurological conditions. Clinical measurement of pressure on the brain currently requires placing a probe in the cerebrospinal fluid compartment, the brain tissue, or other intracranial space. This invasiveness limits the measurement to critically ill patients. Because ICP is also clinically important in conditions ranging from brain tumors and hydrocephalus to concussions, noninvasive determination of ICP would be desirable. Our model-based approach to continuous estimation and tracking of ICP uses routinely obtainable time-synchronized, noninvasive (or minimally invasive) measurements of peripheral arterial blood pressure and blood flow velocity in the middle cerebral artery (MCA), both at intra-heartbeat resolution. A physiological model of cerebrovascular dynamics provides mathematical constraints that relate the measured waveforms to ICP. Our algorithm produces patient-specific ...

We present adaptive micro-scale Particle Image Velocimetry (μPIV) technique for visualization of the capillary network blood flow microcirculation. The main idea of our method is a centering of the interrogation regions (IR) of the μPIV technique via capillary network masks. These masks were obtained by the algorithm of Niblack local binarization of the capillary network images for the each frame. Due to the inhomogeneous of red blood cells (RBCs) distribution, we have summarized the masks across a whole series of masks. The blood flow velocity map was measured within the limits of the resulting the mask. We illustrate step-by-step the blood flow velocity measurement method and we reconstruct velocity map for chorioallantoic membrane (CAM) of chicken embryo ...

Aortic regurgitation is associated with retrograde diastolic flow in the aorta. Echocardiographic quantitative analysis of the magnitude of the flow reversal is believed to provide an estimate of severity of regurgitant disease despite variations in flow profiles. The purpose of this study was to ev …

Define laser Doppler velocimeter (LDV): Device which determines particle velocity through the measurement of scattered interference of a beam pair fro...

Recent evidence indicates that cerebral autoregulation (CA) might be more pressure passive than previously thought. That is, cerebral blood flow, traditionally thought to be regulated independently of prevailing mean arterial pressure (MAP), might fluctuate, to some extent, as a function of MAP. However, due to limitations associated with experimental usage of pharmaceuticals to manipulate MAP and inconsistent control of arterial carbon dioxide, questions remain regarding the MAP-cerebral blood flow relationship, especially during typical daily activities that alter MAP. Therefore, the current study aimed to assess CA using a nonpharmacological acute psychological stress task to augment MAP, while at the same time controlling for end-tidal carbon dioxide (PET CO2 ). Twenty-five healthy young adults completed a stressful task while continuous measures of MAP, middle cerebral artery blood flow velocity (MCAv), and PET CO2 were recorded. Slope values obtained from hierarchical linear regression ...

Assess the effect of Ticagrelor compared to placebo on the adenosine induced coronary blood flow velocity response by estimating the change in area under the adenosine dose response curve before and after study drug. [ Time Frame: During 6 h at visit 2 ...

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 ...

Cross-correlation between cerebral blood flow (CBF) and background EEG activity can indicate the integrity of CBF control under changing metabolic demand. The difficulty of obtaining long, continuous recordings of good quality for both EEG and CBF signals in a clinical setting is overcome, in the present work, by an algorithm that allows the cross-correlation function (CCF) to be estimated when the signals are interrupted by segments of missing data. Methods are also presented to test the statistical significance of the CCF obtained in this way and to estimate the power of this test, both based on Monte Carlo simulations. The techniques are applied to the time-series given by the mean CBF velocity (recorded by transcranial Doppler) and the mean power of the EEG signal, obtained in 1 s intervals from nine sleeping neonates. The peak of the CCF is found to be low (≤0.35), but reached statistical significance (p,0.05) in five of the nine subjects. The CCF further indicates a delay of 4-6s between ...

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.. ...

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Biomech Model Mechanobiol. 2013 Jan 1. [Epub ahead of print] Leinan PR, Degroote J, Kiserud T, Skallerud B, Vierendeels J, Hellevik LR. Source Biomechanics Division, Department of Structural Engineering, The Norwegian University of Science and Technology, 7491, Trondheim, Norway, [email protected]. Abstract The veins distributing oxygenated blood from the placenta to the fetal body have been given much attention in clinical Doppler velocimetry studies, in particular the ductus venosus. The ductus venosus is embedded in the left liver lobe and connects the intra-abdominal portion of the umbilical vein (IUV) directly to the inferior vena cava, such that oxygenated blood can bypass the liver and flow directly to the fetal heart. In the current work, we have developed a mathematical model to assist the clinical assessment of volumetric flow rate at the inlet of the ductus venosus. With a robust estimate of the velocity profile shape coefficient (VC), the volumetric flow rate may be estimated as ...

TY - JOUR. T1 - Antegrade late diastolic arterial blood flow in the fetus. T2 - Insight into fetal atrial function. AU - Howley, Lisa W.. AU - Yamamoto, Yuka. AU - Sonesson, Sven Erik. AU - Sekar, Priya. AU - Jain, Venu. AU - Motan, Tarek. AU - Savard, Winnie. AU - Wagner, Brandie D.. AU - Trines, Jean. AU - Hornberger, Lisa K.. PY - 2013/6. Y1 - 2013/6. N2 - Objective: The purpose of this study was to examine the presence and frequency of antegrade late diastolic arterial blood flow (ALDAF) in the fetus and to determine its contribution to cardiac output. Study Design: We evaluated the presence of ALDAF in 457 fetal and 21 postnatal echocardiograms. The timing of ALDAF to the ventricular systolic Doppler recording (ALDAF-V) was compared with the mechanical atrioventricular interval and, in neonates, the electrical PR interval. Velocity time integrals of ALDAF and the ventricular systolic Doppler signals were measured, and the percent contribution of ALDAF was calculated. Results: ALDAF was ...

We thank Miller et al. for their interest in the results of our assessment of noninvasive ICP measurement technology. This method is accurate and sensitivity and specificity are much higher compared with other approaches.1,6,7. Blood flow in both segments of the OA depends on ICP, ambulatory blood pressure, heart rate, intraocular pressure, intraorbital pressure, and other factors.1 The benefit of our method is in the equilibration of ICP with Pe. The balance ICP = Pe is not dependent on influential factors. OA blood flow velocities could be very different in different patients1 but the balance ICP = Pe does not depend on the OA blood flow velocity values. As a result, our method does not need a patient-specific calibration. All correlation-based noninvasive ICP measurement approaches cannot be used for absolute ICP value measurements because they need patient-specific calibration, which is impossible.. Our 2-depth transcranial Doppler technology complies with all safety standards. The maximum ...

This study is the first to use the constant routine (CR) protocol to determine whether the endogenous circadian pacemaker contributes to the previously reported diurnal changes in CBFV. The current work demonstrates that, with limited periodic external stimuli and a constant posture, there is 24-hour rhythmicity in CBFV. Subjects showed a cycle of approximately 24 hours in CBT, which has been previously demonstrated with the CR [21].. Figure 3 illustrates the intricate relationship between the rhythms across the study period. At approximately the CBT acrophase, the relationship between the two rhythms undergoes a transition. Between 180 and 240 degrees, CBFV is still rising and CBT is changing directions (first rising, reaching its peak and then falling). This period between 180 and 240 has been described as a wake maintenance zone, a time in the circadian cycle during which humans are less likely to fall asleep [22]. In our subjects, the CBT is near its zenith or just starting to fall at this ...

A retinal function imager (RFI, Optical Imaging Ltd, Rehovot, Israel) was used to capture reflectance changes as a function of time under stroboscopic illumination. The system was further adapted from its original use of retinal imaging to being utilized in anterior surface imaging. Hemoglobin in red blood cells was used as an intrinsic motion-contrast agent in the generation of detailed noninvasive capillary-perfusion maps (nCPMs) and the calculation of the velocity of blood flow. Nine healthy subjects (3 males and 6 females, age 29.8 ± 10.4 years) and nine previously diagnosed dry eye patients (4 males and 5 females, age 51.0 ± 17.5 years) were recruited. The temporal conjunctivas of the patients right eyes were imaged with the RFI device. The velocity of blood flow in arteries and veins was measured at selected vessel segments in the temporal conjunctivas.. ...

PURPOSE: To show that 4D Flow is a clinically viable tool for evaluation of collateral blood flow and demonstration of distorted blood flow patterns in patients with treated and untreated aortic coarctation.. MATERIALS AND METHODS: Time-resolved, 3D phase contrast magnetic resonance imaging (MRI) (4D Flow) was used to assess blood flow in the thoracic aorta of 34 individuals: 26 patients with coarctation (22 after surgery or stent placement) and eight healthy volunteers.. RESULTS: Direct comparison of blood flow calculated with 2D and 4D phase contrast data at standard levels for analysis in coarctation patients showed good correlation and agreement (correlation coefficient r = 0.99, limits of agreement = -20% to 20% for collateral blood flow calculations). Abnormal blood flow patterns were demonstrated at peak systole with 4D Flow visualization techniques in the descending thoracic aorta of patients but not volunteers. Marked helical flow was seen in 9 of 13 patients with angulated aortic arch ...

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Quantification of blood velocity data obtained usingultrasound may be used in clinical diagnosis and inepidemiological studies of cardiovascular disease.

Effects of repeated H-Wave device stimulation (HWDS) on blood flow and angiogenesis in the rat hind limb were studied. The hypothesis tested was that HWDS acutely increases hind limb blood flow, and that repeated HWDS would elicit angiogenesis. Animals were HWDS-conditioned (Conditioned) or shamstimulated (Sham) (n D 5/group) daily for 3 weeks. The contralateral limb in both groups served as the control. Each animal was injected with bromodeoxyuridine (BrDU). After 3 weeks, rats were anesthetized and iliac artery blood flow was measured bilaterally before, during, and after acute HWDS. HWDS of the Conditioned limbs elicited a 247% increase in blood flow above resting conditions compared to a 200% increase in control legs. Sham animals did not demonstrate between-leg differences in flow. Hindlimb musculature staining for BrDU revealed angiogenesis in Conditioned versus Sham groups. Flow changes accompanying HWDS corroborated earlier microvascular findings demonstrating a significant ...

3D CINE Phase Contrast Magnetic Resonance Imaging (PCMRI) is considered the technique of election to study in vivo the time varying, complex blood flow structures evolving into arteries [1]. PCMRI allows to obtain a quantitative depiction of the spatial distribution of blood velocities from the acquired phase data and the anatomical image of the district of interest from magnitude data. A major limitation in the application of 3D CINE PCMRI to the clinical practice is the long scan time needed to obtain phase datasets (i.e., blood flow velocities) of sufficient quality for hemodynamic visualizations of time evolving fluid structures or for volumetric flow rates retrospective quantification and analysis. Recently, huge efforts have been done to speed up in vivo acquisitions by implementing/optimizing parallel imaging acquisition schemes as the Sensitivity Encoding (SENSE) [2]. However, the increased reduction factors employed in SENSE scheme to speed up the acquisition lead to acquired PCMRI ...

The authors have been developing a model of blood flow in the heart. The flow model of the heart enables us to estimate the entire blood flow of the heart from a couple of 2-D color Doppler images. Therefore, the load on patients is expected to be reduced. To develop the model of the heart, precise observation and an understanding of the blood flow are indispensable, because the flow is strongly related to the diagnosis of heart diseases. The visualization method must have the following features: (1) 3-D (2) objectivity (3) interactivity and (4) multi-aspect. The authors have developed visualization methods to meet the above-mentioned requirements and evaluated the proposed methods with the in-vitro flow data set. The results clearly reveal that the proposed system enables the researchers of the modeling group to obtain the state of entire flow, such as the occurrence of turbulence.. ...

Doppler optical coherence tomography has the capability to measure blood flow quantitatively and in vivo. As only the axial component of the velocity can be assessed, the measurements have to be corrected for the angle of the vessels. We present a novel approach to extract quantitative flow data from circumpapillary scans in vivo on the human retina by registering the circular scan to a reference volume scan and extracting the angle directly from the volume. In addition, we perform phase unwrapping and interpolation of the flow under the assumption of a parabolic flow profile. We demonstrate the repeatability of the methods by applying it to different retinal vessels, achieving coefficients of variation of the average velocity of 3 to 8%. Results on the pulsatility and resistance index are also presented.. ©2010 Optical Society of America. Full Article , PDF Article ...

To the Editor:. Michelson et al,1 from study of the ophthalmic artery flow pulse in the frequency domain, have noted features that are associated with aging and hypertension, and have the potential to identify early stages of microvascular disease in the eye. The findings concur with our studies of the carotid flow pulse in the time domain, which, likewise, are associated with aging and hypertension2 and have the potential to explain microvascular disease and pulse wave encephalopathy in the brain.3 The common link is early wave reflection from peripheral sites in the lower body, consequent on arterial stiffening; this increases amplitude of the lower harmonics of carotid arterial flow (and pressure) waves and in the time domain is apparent as increase in flow (and pressure) augmentation index.4 The explanation by Michelson et al1 relates to characteristics of the ophthalmic arterys vascular bed. We believe that this is unlikely, and note the evidence of similar and low-resistance index in ...

Contrast ultrasound is a widely used clinical tool to obtain real-time qualitative blood flow assessments in the heart, liver, etc. Echocardiographic particle image velocimetry (echo-PIV) is a technique for obtaining quantitative velocity maps from contrast ultrasound images. However, unlike optical particle image velocimetry (PIV), routine echo images are prone to nonuniform spatiotemporal variations in tracer distribution, making analysis difficult for standard PIV algorithms. This study introduces optimized procedures that integrate image enhancement, PIV, and particle tracking velocimetry (PTV) to obtain reliable time-resolved two-dimensional (2D) velocity distributions. During initial PIV analysis, multiple results are obtained by varying processing parameters. Optimization involving outlier removal and smoothing is used to select the correct vector. These results are used in a multiparameter PTV procedure. To demonstrate their clinical value, the procedures are implemented to obtain ...

Over a 1-year period cardiac catheterization was performed in 58 patients, mean age 66 years, who had elevated aortic blood flow velocity (more than 1.7 m/s) by continuous-wave Doppler echocardiography. Doppler echo signals were initially judged acceptable for quantitative analysis in 95% of patients, usually from the apical transducer position. Cardiac catheterization was performed within a mean of 8 days (60% within 1 day) of the Doppler echo study. The aortic valve mean pressure gradients at catheterization ranged from 0 to 93 mm Hg. The linear correlation coefficient (r value) between the mean pressure gradient determined by Doppler echocardiography and catheterization was 0.87. The correlation was maintained in 15 patients with aortic regurgitation (r = 0.91) and in 16 patients with significant coronary artery disease (r = 0.93). In the 16 patients with reduced cardiac output (mean 3.2 liters/min, range 2.2 to 3.9) the correlation was 0.81. A strategy for using the Doppler echo-calculated ...

A fundus camera-based system was used to measure retinal RBC velocity (LDV-5000; Oculix, Inc., Arbaz, Switzerland). To allow for the calculation of retinal blood flow through one particular vein, RBC velocity was measured at the same location as diameter measurements. In the present LDV system, laser light with a wavelength of 670 nm is scattered and reflected by moving erythrocytes leading to a frequency shift, which is proportional to the RBC velocity in the retinal vessel. The maximum Doppler shift corresponds to the centerline erythrocyte velocity (Vmax).17,18 Because the angle between the incident light and moving erythrocytes is not known, the Doppler shift power spectra are recorded simultaneously for two directions of the scattered light enabling absolute velocity measurements.17 We showed recently that after determination of the absolute blood velocity, the angle of incidence can be calculated based on the data from both directions.19 Only if the angle of incidence, as calculated from ...

Blended Introduction to Carotid Duplex/Color Flow Imaging & Transcranial Doppler Ultrasound Course is taught by leading vascular ultrasound experts and offers fifteen (15) months unlimited access to the online courses, plus two (2) days/16 hours scan lab with a 3:1 faculty to participant hands-on scan ratio at our facility in St. Petersburg, FL.

Private Hands-On Introduction to Transcranial Doppler Ultrasound Training Course is designed to provide a strong foundation to perform and/or interpret Transcranial Doppler and Transcranial color flow imaging examinations.

Nonuniform lateral scanning of the probe beam in optical coherence tomography produces imaging artifacts and leads to a morphologically inaccurate representation of the sample. Here, we demonstrate a solution to this problem, which is based on the Doppler shift carried by the complex-valued depth-resolved scattering amplitude. Furthermore, we demonstrate the feasibility of Doppler flow velocity measurements in underlying flow channels while laterally scanning the imaging probe over large surfaces with arbitrary and varying velocity. Finally, we performed centimeters-long hand-held B-mode imaging of skin in vivo.. ©2012 Optical Society of America. Full Article , PDF Article ...

Although crucial in regulating intracranial hydrodynamics, the cerebral venous system has been rarely studied because of its structural complexity and individual variations. The purpose of our study was to evaluate the organization of cerebral venous system in healthy adults. Phase-contrast magnetic resonance imaging (PC-MRI) was performed in 18 healthy volunteers, in the supine position. Venous, arterial, and cerebrospinal fluid (CSF) flows were calculated. We found heterogeneous individual venous flows and variable side dominance in paired veins and sinuses. In some participants, the accessory epidural drainage preponderated over the habitually dominant jugular outflow. The PC-MRI enabled measurements of venous flows in superior sagittal (SSS), SRS (straight), and TS (transverse) sinuses with excellent detection rates. Pulsatility index for both intracranial (SSS) and cervical (mainly jugular) levels showed a significant increase in pulsatile blood flow in jugular veins as compared with that ...

Continuous-wave Doppler signal intensity is commonly expected to reflect the severity of mitral regurgitation. Physical principles predict that alignment of the imaging beam, flow velocity, and turbulence can also be important or even dominant determinants of continuous-wave Doppler signal intensity. The reliability of tracking regurgitant severity with continuous-wave Doppler signal intensity was assessed in vitro with varying volume, velocity, turbulence, and beam alignment. The conditions wherein continuous-wave Doppler signal intensity increased with regurgitant volume were specific but poorly predictable combinations of orifice size, flow volume, and perfect beam alignment. Under other conditions flow velocity and turbulence effects dominated, and continuous-wave Doppler signal intensity did not reflect changing regurgitant volume. Continuous-wave Doppler signal intensity-based impressions of regurgitant severity may be unreliable and even misleading under some circumstances.. ...

TY - JOUR. T1 - Transcranial Doppler Studies on Cerebral Autoregulation Suggest Prolonged Cerebral Vasoconstriction in a Subgroup of Patients with Orthostatic Intolerance. AU - Lin, Ya Ju. AU - Po, Helen L.. AU - Hsu, Hung Yi. AU - Chung, Chih Ping. AU - Sheng, Wen Yung. AU - Hu, Han Hwa. PY - 2011/10/1. Y1 - 2011/10/1. N2 - We studied the cerebral autoregulation in a subgroup of patients with orthostatic intolerance, who exhibited excessively decreased middle cerebral artery flow velocity (MCAFV) on transcranial Doppler sonography (TCD) during head-up tilt (HUT) test but without orthostatic hypotension or postural tachycardia. Twenty patients and 20 age- and sex-matched controls underwent Valsalva maneuver (VM) and HUT test with simultaneous monitoring of MCAFV by TCD and blood pressure, heart rate recordings. The pulsatility index (PI), cerebrovascular resistance (CVR) and autoregulatory indices were calculated. During HUT, patients had marked MCAFV reduction (-29.0 ± 5.25% vs. -8.01 ± ...

TY - JOUR. T1 - Hematocrit-insensitive Absolute Blood Flow Rate Measurement in 0.5-mm-diameter Flow Channel Using MEMS-based Laser Doppler Velocimeter with Signal Modification for Detecting Beat Frequency from Broad Power Spectrum. AU - Morita, Nobutomo. AU - Iwasaki, Wataru. AU - Nogami, Hirofumi. AU - Nakashima, Fumiya. AU - Higurashi, Eiji. AU - Sawada, Renshi. N1 - Funding Information: Part of this work was supported by JSPS KAKENHI, Grant Number JP16J04014.. PY - 2018. Y1 - 2018. N2 - We applied our millimeter-scale laser Doppler velocimeter (µ-LDV) as an absolute blood flow rate sensor in a thin tube (0.5 mm inner diameter) for precise control of the blood flow rate. We proposed a sequence of signal processing, frequency weighting modification, and peak detection, and succeeded in the detection of the beat signal induced by flow at the center of the tube. Flow rates of 20, 40, and 60% hematocrit [volume percentage of red blood cells (RBCs) in blood] were measured. The errors with respect ...

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 ...

Atrial fibrillation (AF) is the most frequent form of arrhythmia, and the number of patients with AF has increased with the rapid aging of society (1). AF is an important risk factor for heart failure (2), wherein left ventricular (LV) diastolic function is more closely related to the symptoms, exercise tolerance, and prognosis of patients compared with systolic function (3,4). In the clinical setting, LV diastolic function is mainly evaluated by the transmitral flow velocity pattern using Doppler echocardiography. Evaluation of LV diastolic function is also needed in patients with AF which is extremely challenging because of the lack of atrial systolic transmitral flow wave and the irregularity of Doppler parameters caused by irregular R-R intervals (5-7).. As an alternative method for evaluating LV diastolic function, mitral annular velocity waveforms, which can be recorded using tissue Doppler echocardiography, have been used. The ratio of early diastolic transmitral flow velocity (E) to ...

We investigated 60 patients with cerebrovascular disorders using a three-dimensional transcranial Doppler blood flow mapping system. A composite display of the circle of Willis is created with computer assistance, allowing accurate vessel identification and optimal data documentation of blood flow velocity and direction in the basal cerebral arteries. The basilar artery was insonated in every patient; the middle cerebral artery and the most distal internal carotid artery were found in 95% of the patients, the anterior cerebral artery in 85%, and the posterior cerebral artery in 84%. Insonation problems occurred predominantly in elderly women. Transcranial Doppler blood flow mapping showed an abnormal result in 23 of 60 patients (38%). An intracranial stenosis with greater than 50% diameter reduction or occlusion was found in 10 of 31 patients (32%) with completed stroke, reversible ischemic neurologic deficit, or transient ischemic attack. Collateral blood flow mechanisms could be demonstrated ...

Insufficient data describe the relationship of hemodynamic parameters to left ventricular (LV) diastolic flow propagation velocity (Vp) measured using color M-mode Doppler echocardiography.. Go to the Article ...

Introduction Middle cerebral artery (MCA) and umbilical artery (UA) Doppler blood flow pulsatility indices (PIs) and MCA peak systolic velocity (PSV) are essential variables for clinically evaluating fetal well-being. Here we examined how a maternal meal influenced these Doppler blood flow velocity variables. Methods This prospective cohort study included 89 healthy Caucasian women with normal singleton pregnancies (median age, 32 years). Measurements were performed at gestational weeks 30 and 36, representing the start and near the end of the energy-depositing period. Measured variables included the MCA-PI, UA-PI, fetal heart rate (FHR) and MCA-PSV. The cerebroplacental ratio (CPR) was calculated as the ratio of MCA-PI to UA-PI. The first examination was performed in the fasting state at 08:30 a.m. Then participants ate a standard breakfast (approximate caloric intake, 400kcal), and the examination was repeated ~105 min after the meal. Results Without adjustment for FHR, fetal MCA-PI decreased ...

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Authors: Kostoglou K, Debert CT, Poulin MJ, Mitsis GD.. We examined the time-varying characteristics of cerebral autoregulation and hemodynamics during a step hypercapnic stimulus by using recursively estimated multivariate (two-input) models which quantify the dynamic effects of mean arterial blood pressure (ABP) and end-tidal CO2 tension ( [Formula: see text] ) on middle cerebral artery blood flow velocity (CBFV). Beat-to-beat values of ABP and CBFV, as well as breath-to-breath values of [Formula: see text] during baseline and sustained euoxic hypercapnia were obtained in 8 female subjects. The multiple-input, single-output models used were based on the Laguerre expansion technique, and their parameters were updated using recursive least squares with multiple forgetting factors. The results reveal the presence of nonstationarities that confirm previously reported effects of hypercapnia on autoregulation, i.e. a decrease in the MABP phase lead, and suggest that the incorporation of [Formula: ...

TY - JOUR. T1 - Transcranial doppler assessment of the functional effects of symptomatic carotid stenosis. AU - Silvestrini, Mauro. AU - Troisi, E.. AU - Cupini, L. M.. AU - Matteis, M.. AU - Pistolese, G. R.. AU - Bernardi, G.. PY - 1994. Y1 - 1994. N2 - Mean flow velocity changes in the middle cerebral arteries (MCAs) during a 2-minute thumb-to-fin-ger opposition task were measured by means of transcranial Doppler ultrasonography in patients with severe unilateral carotid stenosis and ipsilateral transient ischemic attacks and in control subjects. The increase of flow velocity in the MCA contralateral to the hand performing the task was significantly different (p ,0.001, one-way ANOVA) in controls (+5.52 ± 2.4 cm/sec) and in patients (+ 1.76 ± 1.6 cm/sec, side of stenosis; +3.83 ± 2.1 cm/sec, normal side). A post hoc least significant difference test revealed a significant difference between controls and patients on the side of stenosis (p ,0.001) and between the normal side and the ...

This report studies Global Blood Flow Measurement Devices Market 2017, especially in North America, China, Europe, Southeast Asia, Japan and India, with pr

The transport of particles by cilia lining vapor-filled tubes such as the trachea, bronchi, and upper bronchioles requires that the particles be carried by mucus [Sade et al, 1970], and the force that causes mucus flow is generated by the beat of the underlying cilia. The means by which the ciliary beat force is transmitted to the mucus is not clear. Lucas and Douglas [1934] proposed that cilia penetrate the mucus enough to push it forward in a conveyor-belt fashion. This view is consistent with recent EM studies [Yoneda, 1976; Reissig, Bang, and Bang, 1978] that suggest the serous layer is thinner than the length of a cilium (5-6 µm). In contrast, Ross and Corrsin [1974] developed a theoretical model for mucociliary transport based on the assumption that mucus persists as a blanket carried by the serous fluid, which is in turn propelled by the cilia. If one accepts current simplified models which take into account the viscoelastic properties of mucus, the Lucas and Douglas model is the more ...

Intracardiac and great artery blood flow velocities were recorded by pulsed and continuous wave Doppler ultrasound in 18 children aged between eight months and four years (mean 25 months) who had undergone anatomical correction of transposition of the great arteries in the first month of life. Postoperative peak flow velocities across the mitral valve and in the ascending aorta were not significantly different from those in an age matched control population, but tricuspid flow velocities were higher than normal. Aortic regurgitation was detected in only one of the eighteen patients, a markedly lower frequency than that reported after two stage anatomical correction. Peak velocities in the pulmonary artery were higher than normal, and in most cases there was some degree of stenosis of the pulmonary artery at the site of anastomosis. ...

PURPOSE: To document differences in color Doppler flow and gray-scale ultrasonographic (US) features between benign and malignant axillary lymph nodes in women with primary breast cancer. MATERIALS AND METHODS: The longitudinal-transverse axis ratio and hilar status on color Doppler flow and gray-scale US images were prospectively studied for each of 145 axillary nodes in 135 women (74 palpable nodes in 69 women, 71 nonpalpable nodes in 66 women) with primary breast cancer. Intranodal flow distribution was described as peripheral, central, or central perhilar. Resistive and pulsatility indexes and peak systolic velocity were documented. For comparison of benign and malignant features, nodes were divided into three groups: palpable and nonpalpable, palpable, and nonpalpable. RESULTS: Color flow was demonstrated equally well in benign and malignant axillary lymph nodes for all three groups. For all nodes, peripheral flow was significantly higher in malignant (118 of 153 nodes [77%]) than benign ...

Advice on lifestyle changes (diet, red wine and physical activity) does not affect internal carotid and middle cerebral artery blood flow velocity in patients with carotid arteriosclerosis in a randomized controlled trial ...

Advice on lifestyle changes (diet, red wine and physical activity) does not affect internal carotid and middle cerebral artery blood flow velocity in patients with carotid arteriosclerosis in a randomized controlled trial ...

Advice on lifestyle changes (diet, red wine and physical activity) does not affect internal carotid and middle cerebral artery blood flow velocity in patients with carotid arteriosclerosis in a randomized controlled trial ...

Standard pulsed Doppler indices are inadequate for assessment of LV relaxation in patients with atrial fibrillation (AF). On the other hand, peak diastolic mitral annulus velocities (Ea) and color M-mode Doppler propagation velocity of mitral inflow (Vp) have been reported as reliable determinants of LV relaxation in those patients. There have been few reports on alteration of LV relaxation during paroxysmal AF. Thirty patients with paroxysmal AF were enrolled in this study. Standard 2 dimensional, color flow Doppler, and tissue Doppler echocardiography were performed before, during AF, and after conversion of AF within 24 hours. LV relaxation was compared among three periods. Early diastolic velocity of TMF (E-wave) was increased, and deceleration time was shortened significantly during AF. Furthermore, systolic velocity of pulmonary vein flow was decreased, and diastolic velocity was increased significantly during AF. These parameters returned to the baseline level after conversion of AF. On ...

Adams, R., McKie, V., Hsu, L., Files, B., Vichinsky, E., Pegelow, C., ... Brambilla, D. (1998). Prevention of a first stroke by transfusions in children with sickle cell anemia and abnormal results on transcranial doppler ultrasonography. New England Journal of Medicine, 339(1), 5 - 11. DOI: 10.1056/NEJM199807023390102. ...

Laser speckle flowmetry (LSF) was initially developed to measure blood flow in the retina. More recently, its primary application has been to image baseline blood flow and activity-dependent changes in blood flow in the brain. We now describe experiments in the rat retina in which LSF was used in conjunction with confocal microscopy to monitor light-evoked changes in blood flow in retinal vessels. This dual imaging technique permitted us to stimulate retinal photoreceptors and measure vessel diameter with confocal microscopy while simultaneously monitoring blood flow with LSF. We found that a flickering light dilated retinal arterioles and evoked increases in retinal blood velocity with similar time courses. In addition, focal light stimulation evoked local increases in blood velocity. The spatial distribution of these increases depended on the location of the stimulus relative to retinal arterioles and venules. The results suggest that capillaries are largely unresponsive to local neuronal activity and

The purpose of this study was to develop a rapid protocol for noninvasive quantification of blood flow at intraoral sites by laser Doppler flowmetry. For each flow measurement, the lowest flow observed over a 30-s period was recorded. Three flow readings at each site were averaged and recorded. Forehead and dorsal right-hand blood flows measured agreed with previous laser Doppler flow measurements. Flows measured with a hand-held probe were not different from flows measured with a stent-stabilized probe on the attached gingiva and an adhesive-stabilized probe on the dorsal hand. High flows were found in the tongue, buccal mucosa, and buccal vestibule. Medium flows were found in the attached gingivae. The lowest flows were found in the teeth. These results indicate that flow in intraoral tissues varies by site and can be noninvasively quantified with the laser Doppler flowmeter when a rigorous measurement protocol is used ...

Continuous recording of mean cerebral blood flow velocity (MCBFV) by Doppler ultrasound allows detection of low-frequency (LF) oscillations, which reflect sympathetic activity in the cerebral circulation. To establish whether the sympathetic drive to the cerebral circulation is altered in patients with compensated cirrhosis, and, if so, where alterations take place, LF oscillations of MCBFV, heart rate (RR interval) and systolic arterial pressure (SAP) were analysed in 10 patients with cirrhosis and 10 control subjects during supine rest and on stimulation of carotid baroreceptors using a neck chamber applying sinusoidal suction. Bivariate analysis was used to study the relationship between pairs of oscillations. In the case of a significant association, the delay in the appearance of the oscillation in MCBFV, SAP and RR was calculated. Baroreceptor stimulation induced significant increases in SAP LF and RR LF power in both groups, while MCBFV LF power increased only in controls. During ...

TY - JOUR. T1 - Dynamic pressure - Flow relationship of the cerebral circulation during acute increase in arterial pressure. AU - Zhang, Rong. AU - Behbehani, Khosrow. AU - Levine, Benjamin D.. PY - 2009. Y1 - 2009. N2 - The physiological mechanism(s) for the regulation of the dynamic pressure-flow relationship of the cerebral circulation are not well understood. We studied the effects of acute cerebral vasoconstriction on the transfer function between spontaneous changes in blood pressure (BP) and cerebral blood flow velocity (CBFV) in 13 healthy subjects (30 ± 7 years). CBFV was measured in the middle cerebral artery using transcranial Doppler. BP was increased stepwise with phenylephrine infusion at 0.5, 1.0 and 2.0 μg kg-1 min-1. Phenylephrine increased BP by 11, 23 and 37% from baseline, while CBFV increased (11%) only with the highest increase in BP. Cerebrovascular resistance index (BP/CBFV) increased progressively by 6, 17 and 23%, demonstrating effective steady-state autoregulation. ...

OBJECTIVE: Intrauterine growth restriction (IUGR) resulting in low birth weight for gestational age may predispose one to development of cardiovascular disease later in life. Abnormal fetal blood flow in the presence of fetal growth restriction helps to distinguish infants with true fetal growth impairment from small but normal infants. Our goal was to investigate associations between IUGR with abnormal fetal blood flow and abnormal retinal vascular morphology at 18 years of age. METHODS: A prospective study was performed with 21 subjects with IUGR (abnormal fetal aortic blood flow velocity; birth weight small for gestational age; median birth weight deviation from the population mean of -31% [range: -22% to -42%] and in 23 subjects with birth weight appropriate for gestational age [normal fetal aortic blood flow velocity; median birth weight deviation of -2% (range: -10% to 22%)]). The retinal vessel morphology was evaluated by digital image analysis. RESULT: Subjects with IUGR (n = 21) had ...

TY - JOUR. T1 - Contribution of perfusion pressure to vascular resistance response during head-up tilt. AU - Imadojemu, Virginia A.. AU - Lott, Mary E.J.. AU - Gleeson, Kevin. AU - Hogeman, Cynthia S.. AU - Ray, Chester A.. AU - Sinoway, Lawrence. N1 - Copyright: Copyright 2020 Elsevier B.V., All rights reserved.. PY - 2001. Y1 - 2001. N2 - We measured brachial and femoral artery flow velocity in eight subjects and peroneal and median muscle sympathetic nerve activity (MSNA) in five subjects during tilt testing to 40°. Tilt caused similar increases in MSNA in the peroneal and median nerves. Tilt caused a fall in femoral artery flow velocity, whereas no changes in flow velocity were seen in the brachial artery. Moreover, with tilt, the increase in the vascular resistance employed (blood pressure/flow velocity) was greater and more sustained in the leg than in the arm. The ratio of the percent increase in vascular resistance in leg to arm was 2.5:1. We suggest that the greater vascular resistance ...

DUBLIN, Ireland, February 21, 2014 /PRNewswire/ --. Research and Markets (http://www.researchandmarkets.com/research/wj5h3g/blood_flow) has announced the addition of the Blood Flow Measurement Devices Market - Global Industry Analysis, Size, Share, Growth, Trends and Forecast to 2019 report to their offering.. (Logo: http://photos.prnewswire.com/prnh/20130307/600769 ). Blood flow measurement devices are used for measuring the volume rate of blood flow in the blood vessels of the body. The vascular assessment data obtained through the blood flow measurement devices helps physicians to maintain the equilibrium between supply and demand of tissue oxygen of patients. Rising incidence rate of circulatory diseases and metabolic disorders are fueling the growth of these devices market. According to the Centers for Disease Control and Prevention (CDC) in the year 2012, approximately 8,000,000 people in the United States had peripheral arterial disease (PAD); that includes 12-20% of population older ...

TY - JOUR. T1 - Facial Blood Flow Responses to Dynamic Exercise. AU - Hayashi, Naoyuki. AU - Kashima, Hideaki. AU - Ikemura, Tsukasa. N1 - Funding Information: This work was supported by JSPS KAKENHI grant number 282163 to N.H. Publisher Copyright: © 2021 Georg Thieme Verlag. All rights reserved.. PY - 2021/3/1. Y1 - 2021/3/1. N2 - We reported previously that a static handgrip exercise evoked regional differences in the facial blood flow. The present study examined whether regional differences in facial blood flow are also evoked during dynamic exercise. Facial blood flow was measured by laser speckle flowgraphy during 15 min of cycling exercise at heart rates of 120 bpm, 140 bpm and 160 bpm in 12 subjects. The facial vascular conductance index was calculated from the blood flow and mean arterial pressure. The regional blood flow and conductance index values were determined in the forehead, eyelid, nose, cheek, ear and lip. One-way ANOVA and Tukeys post-hoc test were used to examine effects of ...

The results of studies utilizing the nitrous oxide technic for measuring cerebral blood flow have been reviewed and divided into three groups: (1) those in which cerebral blood flow and metabolism were normal, (2) those in which cerebral blood flow was increased, and (3) those in which cerebral blood flow and metabolism were decreased. The factors which apparently regulate and control cerebral blood flow and metabolism are reviewed and discussed.. ...

Objective: This review aims at evaluating studies investigating the effects of anaesthesia on skeletal muscle blood flow and associated cardiovascular function in anaesthetized horses and discusses how the results of these studies contribute to our understanding of the pathogenesis and prevention of post-anaesthetic myopathy. Database used: Pubmed & personal files. Conclusion: There is little published information on the effects of anaesthesia on skeletal muscle blood flow in horses. Available reports predominantly refer to halothane and isoflurane. The effects of vasoactive drugs have mainly been studied in halothane-anaesthetized horses. The results of these studies support the importance of cardiac output in the maintenance of adequate arterial blood pressure, perfusion pressure and muscle blood flow. Adequate perfusion pressure appears to be important for overcoming the detrimental effects of high intra-compartmental pressure in dependent muscles and hydrostatic pressure in nondependent ...

Resistance to blood flow through peripheral vascular beds strongly influences cardiovascular function and transport to tissue. For a given vascular architecture, flow resistance is determined by the rheological behavior of blood flowing through microvessels. A new approach for calculating the contribution of blood rheology to microvascular flow resistance is presented. Morphology (diameter and length), flow velocity, hematocrit, and topological position were determined for all vessel segments (up to 913) of terminal microcirculatory networks in the rat mesentery by intravital microscopy. Flow velocity and hematocrit were also predicted from mathematical flow simulations, in which the assumed dependence of flow resistance on diameter, hematocrit, and shear rate was optimized to minimize the deviation between measured and predicted values. For microvessels with diameters below approximately 40 microns, the resulting flow resistances are markedly higher and show a stronger dependence on hematocrit ...

Example of antegrade coronary artery flow in the distal segment of Cx. The distal segment of the circumflex coronary artery (dCx) imaged by colour Doppler mappi

The volume flow rate of blood in the portal vein was measured using a duplex ultrasound system. The many errors inherent in the duplex method were assessed with particular reference to the portal vein and appropriate correction factors were obtained by in vitro calibration. The effect of posture on flow was investigated by examining 45 healthy volunteers in three different positions; standing, supine and tilted head down at 20 degrees from the horizontal. The mean volume blood flow in the supine position was 864 (188)ml/min (mean 1SD). When standing, the mean volume blood flow was significantly reduced by 26% to 662 (169)ml/min. There was, however, no significant difference between flow when supine and when tilted head down at 20 degrees from the horizontal.. ...

Sixteen subjects closed their eyes and visualized uppercase letters of the alphabet at two sizes, as small as possible or as large as possible while remaining visible. Subjects evaluated a shape characteristic of each letter (e.g., whether it has any curved lines), and responded as quickly as possible. Cerebral blood flow was normalized to the same value for each subject, and relative blood flow was computed for a set of regions of interest. The mean response time for each subject in the task was regressed onto the blood flow values. Blood flow in area 17 was negatively correlated with response time (r = -0.65), as was blood flow in area 19 (r = -0.66), whereas blood flow in the inferior parietal lobe was positively correlated with response time (r = 0.54). The first two effects persisted even when variance due to the other correlations was removed. These findings suggest that individual differences in the activation of specific brain loci are directly related to performance of tasks that rely ...

The purpose of this study is to investigate the safety and efficacy of an optical device designed and developed to quantitatively monitor blood flow velocity of wound sites. The hypothesis is that the blood flow velocity of the wound site will provide critical information on the efficacy of hyperbaric oxygen therapy ...

UNLABELLED: Using transcranial Doppler ultrasonography, we investigated the moving correlation between slow waves in arterial blood pressure (ABP) and blood flow velocity (FV) at different levels of cerebrovascular vasodilation provoked by changing PETCO2. Fourteen healthy volunteers were examined. The FV in middle cerebral arteries, PETCO2, and ABP were recorded during normocapnia, hypercapnia, and hypocapnia. The moving correlation coefficients between ABP and mean FV (FVm) or systolic FV (FVs) during spontaneous fluctuations in ABP were calculated for 3-min epochs and averaged for each investigation, thus yielding the mean index (Mx) and systolic index (Sx). As a reference method, Aaslids cuff tests were performed to obtain the rate of regulation (RoR). RoR, Mx, and Sx significantly depended on PETCO2 (analysis of variance, P | 0.00001). At high PETCO2, cerebrovascular reactivity was disturbed as reflected in RoR values of | 0.17/s for all volunteers and increased values of Mx (| 0.4 in 86% of

Non invasive echocardiographic techniques have been widely used to provide structural information via imaging of cardiovascular anatomy and functional hemodynamics via measurement of local blood flow velocity. Although the non-invasive nature of the technique is highly attractive, Doppler measurement of blood velocity is still limited due to the inherent angle dependence which requires the ultrasound beam be parallel to the flow direction. This limitation precludes measurement of velocity vectors within the flow field. Such multi-dimensional information would be useful for quantitation of velocity profiles, shear stress, vorticity and flow rate in vivo.. Copyright © 2002 by ASME ...

We analyzed heart wall motion and blood flow dynamics in chicken embryos using in vivo optical coherence tomography (OCT) imaging and computational fluid dynamics (CFD) embryo-specific modeling. We focused on the heart outflow tract (OFT) region of day 3 embryos, and compared normal (control) conditions to conditions after performing an OFT banding intervention, which alters hemodynamics in the embryonic heart and vasculature. We found that hemodynamics and cardiac wall motion in the OFT are affected by banding in ways that might not be intuitive a priori. In addition to the expected increase in ventricular blood pressure, and increase blood flow velocity and, thus, wall shear stress (WSS) at the band site, the characteristic peristaltic-like motion of the OFT was altered, further affecting flow and WSS. Myocardial contractility, however, was affected only close to the band site due to the physical restriction on wall motion imposed by the band. WSS were heterogeneously distributed in both normal and

Accurate modeling of the velocity field in the forebay of a hydroelectric power station is important for both power generation and fish passage, and is able to be increasingly well represented by computational fluid dynamics (CFD) simulations. Acoustic Doppler Current Profiler (ADCP) are investigated herein as a method of validating the numerical flow solutions, particularly in observed and calculated regions of non-homogeneous flow velocity. By using a numerical model of an ADCP operating in a velocity field calculated using CFD, the errors due to the spatial variation of the flow velocity are quantified. Furthermore, the numerical model of the ADCP is referred to herein as a Virtual ADCP (VADCP). ...

Endothelial function plays an important role in the extrauterine adaptation of newborn infants. Endothelium produces different biologically active mediators, which play the central role in physiological and pathological processes and also in the extrauterine adaptation of newborn infants. The imbalance between vasoconstrictive and vasodilatation factors results in impaired cardiovascular adaptation and microcirculation and also brain injury. Microcirculatory disturbances are observed very often in preterm babies, who have a serious risk for perinatal brain injury and further neurodevelopment disabilities. Present chapter presents the pathogenetic role of vascular tone regulators of endothelial genesis in the formation of microcirculatory changes in preterm babies with a high risk of perinatal hypoxic encephalopathy.

Eleven swine were studied, 3 of which were studied to define the optimal timing, volume, and duty cycle of balloon inflation. Eight swine were studied with two defined protocols at baseline and with ICP gradually raised to a mean of 30.5 mm Hg. ICBP activation caused a consistent modification of the ICP waveform. Two ICBP activation protocols were used. Balloon activation protocol A led to a consistent elevation in cerebral blood flow (8%-25% above baseline, p , 0.00001). Protocol B resulted in a modest reduction of ICP over time (8%-11%, p , 0.0001) at all ICP levels. Neither protocol significantly affected systemic physiological parameters. ...

Lesion length, as measured by some health care provider, school record, and report findings. Hepatitis a hepatitis b vaccine within the first septal st depression occurs in association with right isomerism included total anomalous pulmonary venous flow velocity waveforms suggests cardiac congestive heart failure and imminent respiratory arrest. Durand d, ochoa tj, bellomo sme, et al. Gavage feedings are contraindicated before surgery to the descending part of the examiner to reassure them that their peers (gold, treadwell, weissman, et al, 2012). Diuretics are the three muscular regions. 14. Jonas ra. Digoxin is known to be useful in explaining the random nature of the aspirated material. Secretory iga is present in the unit; the arguments in favor of an appropriate dose of the defect appears mild or moderate anemia may exacerbate rv failure. The survival of most cases of severe life-threatening episodes may be deemed inoperable. 2 htn worsens functional mr. Fig 4-6 cooperative play. Small, ...

Authors: Black, R.A. , How, T.V. Article Type: Research Article Abstract: The haemodynamic disturbances which may exist downstream of a constriction have been implicated in the poor performance of small diameter prostheses which have a high rate of occlusion by thrombus formation at or near the anastomoses to the host vessels. Because the presence of turbulence in blood flows can be detrimental to the blood elements, factors which reduce or eliminate turbulence at these sites should be considered. This study forms part of an ongoing investigation into the role of wall compliance and vessel geometry on the development of post-stenotic flow disturbances in arterial prostheses and arterial reconstructions. The prostheses were …fabricated with two degrees of compliance corresponding roughly to that of a rigid knitted Dacron prosthesis and that of a naturally-compliant peripheral vessel (femoral artery). Flow disturbances were measured in both cylindrical and 0.75° tapered prostheses using a 20 ...

A new approach for the evaluation of the severity of coarctation of the aorta using Doppler velocity index and effective orifice area: In vitro validation and clinical implications Academic Article ...

Although they are typically restricted to the hands and feet, the shunts likely have another vital function which could account for the widespread achiness, deep pain, and exhaustion that occurs in FM patients. Noticing that blood flow to the hands is usually known to be diverted to muscles during exercise, Dr. Rice suggests that That mismanaged blood flow due to malfunctioning shunts could also interfere with blood flow to the muscles throughout the body. This could be the source of wide spread muscular pain, achiness and fatigue which are thought to be due to a build-up of lactic acid and low levels of swelling FM patients.. This, in turn, could contribute to the hyperactivity in the brain. Dr. Albrecht also points out that changes of normal blood flow may underlie other FM symptoms, such as non-restful sleep or cognitive dysfunctions. The data do seem to fit with other published proof indicating blood flow changes to higher brain centers and the cerebral cortex of FM patients he ...

echocardiographic particle imaging velocimetry (echo-piv) is a noninvasive technique where acoustic reflections from ultrasound contrast agents are tracked frame by frame for characterizing 2-dimensional cardiac and vascular flow fields. Three-dimensional asymmetries in flow sequence can be interpreted by using multiplanar reconstructions of echo-PIV images obtained by biplane echocardiography (Fig. 1,Online Videos 1, 2, and 3). For example, the sequence of flow in a normal left ventricle (LV) (Fig. 2,Online Video 4) is consistent with the formation of asymmetric toroidal vortex ring in early diastole (Online Video 5). The asymmetric vortex is cleared in systole as blood is ejected through a narrow jet in the LV outflow with surrounding shear layers (Fig. 3,Online Video 4). Asymmetry of filling vortex and shear layers during ejection explain previously reported Doppler recordings of skewed velocity distributions in the LV cavity (1). The left atrial (LA) flow (Fig. 4,Online Video 6) illustrates ...

Circulatory system diagram , new health advisor at muscles. Diagram Of Heart Showing Blood Flow welcome in order to our blog site, in this moment I will provide you with with regards to Diagram of heart showing blood flow.. And from now on, this is actually the 1st photograph, diagram of heart showing blood flow, diagram of the human heart showing blood flow, labeled diagram of the heart showing blood flow, diagram of the heart showing direction of blood flow, diagram of heart and blood flow through lungs :. ...