Coronary flow velocity reserve (CFVR) is conventionally obtained by manual tracings of Doppler profiles, as ratio of stress vs baseline diastolic peak velocity. When <1.9, this parameter evidences reduced coronary flow and possible microcirculatory disease. Our goals were: 1) to develop a novel technique for semi-automated detection of Doppler flow ...

The measurement of blood-plasma velocity distributions with spatial and temporal resolution in vivo is inevitable for the determination of shear stress distributions in complex geometries at unsteady flow conditions like in the beating heart. A non-intrusive, whole-field velocity measurement technique is required that is capable of measuring instantaneous flow fields ...

OBJECTIVE: We aimed to evaluate myocardial diastolic function in patients with beta-thalassemia major (beta-TM) using pulsed-tissue Doppler imaging (TDI) and flow propagation (VP), in relation to BNP levels. METHODS: We enrolled 192 consecutive patients with beta-TM (88 men (25 +/- 6 years) and 104 women (26 +/- 6 years), with ...

BACKGROUND AND PURPOSE: Nitric oxide (NO)/endothelin imbalance may play a role in the regulation of cerebral blood flow. The aim of the present study was to assess whether these endothelial factors influence middle cerebral artery blood flow velocities (MCAV) and cerebrovascular reactivity (CVR) in healthy and hypertensive adolescents. SUBJECTS AND ...

PURPOSE: The blood flow inside distal end-to-side anastomoses may be affected by inlet flow velocity profiles and outlet blood distribution ratios. This study investigated the in vivo range of these variables and their impact on the hemodynamic effects of an anastomotic cuff using a computational fluid dynamics approach. MATERIALS AND ...

In order to analyze cerebral hemodynamics and its change following neural activation, the cross-sectional profiles of blood flow velocity in the rat pial microvessels and their temporal changes were measured in vivo using Doppler OCT technique (Doppler optical coherence tomography). The OCT system used in this study has axial resolution ...

OBJECTIVE: Our purpose was to determine normative data for maternal cerebral blood flow indices. Study design. A prospective longitudinal study. METHODS: The maternal middle cerebral artery was examined by transcranial Doppler ultrasound in 14 healthy women before (0-10 months prior to conception) and during pregnancy (at 8, 15, 22, 29, ...

A family of velocity-selective pulses consisting of a series of RF hard pulses followed by bipolar gradients was designed. The succession of required pulses was deduced using a k-space approach within a small tip-angle approximation. Fourier transform of the desired velocity excitation determined the flip-angle series, and the corresponding position ...

Tissue microcirculation, as measured by laser Doppler flowmetry (LDF), comprises capillary, arterial, and venous blood flow. With the classical LDF approach, it has been impossible to differentiate between different vascular compartments. We suggest an alternative LDF algorithm that estimates at least three concentration measures of flowing red blood cells (RBCs), ...

A new method for flow velocity mapping is presented here. Instead of the conventional approach of employing two images (velocity sensitive and control) to generate velocity information, in the new method one determines the velocity directly from a single-shot acquisition by solving an inverse problem. This technique is a variant ...

The purely refractive index driven separation of uniformly sized polystyrene, n = 1.59 and poly(methylmethacrylate), n = 1.49 in an optical chromatography system has been enhanced through the incorporation of a custom poly(dimethysiloxane) (PDMS) microfluidic system. A customized channel geometry was used to create separate regions with different linear flow ...

In recent years, the use of RigiScan and ultrasound to assess erectile dysfunction has fallen from favour. However, in a small minority of specialist cases, where a vascular, neurogenic or psychogenic aetiology requires confirmation, there remains a need for further investigation. To establish if in a preliminary assessment the use ...

OBJECTIVES: We sought to assess the effects of blood donation on different echocardiographic parameters in healthy volunteers. METHODS: A total of 101 healthy male volunteers were evaluated by echocardiography before and immediately after a 500-mL blood donation. In addition to traditional Doppler indices of left ventricular filling, Doppler tissue, color ...

The presence of spontaneous echocontrast (SEC) in the left atrium (LA) or LA appendage (LAA) has been associated with a higher risk of thromboembolism and cerebrovascular accidents. The purpose of this study was to define the new transesophageal echocardiographic predictors of SEC for patients with stroke and atrial fibrillation. We ...

AIM: Sequential leg compression has been previously shown to be superior to uniform compression. The aim of our study was to compare the hemodynamic effectiveness of the portable sequential compression device (SCD Express Compression System, Tyco Healthcare Group LP, Mansfield, MA, USA) with a rapid inflation device (VenaFlow, Aircast, Inc, ...

Reduced cerebral blood flow after severe head injury results in an increased risk of ischemic brain damage. Blood flow should therefore be monitored with a simple, reliable method. Transcranial color-coded Doppler sonography (TCCS) is an accepted tool for the diagnosis of cerebral vasospasm; however, its usefulness in evaluating patients with ...

OBJECTIVES: This study applied dynamic cerebral autoregulation (DCA) testing distally to severe bilateral vertebral artery disease (BVAD). METHODS: Using continuous monitoring of beat-to-beat blood pressure and transcranial Doppler of the posterior cerebral arteries (PCA) were examined in 20 patients with BVAD and 22 controls. DCA testing was based on the ...

The vascular responses to mental task in visceral arteries in humans have not been elucidated. We observed the responses in the renal (RA) and superior mesenteric (SMA) arteries to mental stress, using simultaneous pulsed and echo Doppler ultrasound flowmetry. Nine healthy females performed a computerized colour word conflict test (CWT) ...

The effects of current velocity on the foraging behavior of false dace, Pseudorasbora parva, were examined in a zero velocity (stagnant) condition, and at four flow rates (5, 7, 11 and 16 cm per second). In stagnant water, the fish displayed a cruise-searching pattern, but they used a drift-feeding foraging ...

Decreased cerebral flow velocities in Parkinsonian patients were reported previously. Because of the limited data on vascular changes in Parkinson disease (PD), which may have a vascular etiology, we aimed to disclose any possible cerebral hemodynamic alteration in Parkinsonian patients. We prospectively evaluated 28 non-demented, idiopathic parkinsonian patients and 19 ...

This paper presents a new model of dispersion of components in transport processes. It is suggested that the flow velocity may be specified by a Gauss function with relative dispersion of flow velocity beta=sigmav/v; the overall dispersion of inert component (in porous as well as in homogeneous medium) may be ...

AIM: To assess the cerebral blood flow velocity during the first minute of head-up tilt in patients with postural tachycardia syndrome (POTS) or neurally-mediated reflex syncope compared with patients with dizziness. METHODS: We evaluated 120 patients selected from 470 patients who underwent head-up tilt testing: 40 with POTS, 40 with ...

Doppler spectra of the abdominal aorta (AAo), cranial mesenteric artery (CMA), celiac artery (CA), and left renal artery (LRA) were obtained from 11 fasted, clinically healthy, conscious Beagles before and after inducing severe acute normovolemic anemia (mean +/- standard deviation hematocrit 16.0 +/- 0.77%). Peak systolic, end diastolic, and time-averaged ...

BACKGROUND: When the ductus arteriosus (DA) is patent, the ductal shunt is proportional to the ratio of left ventricular output (LVO) to systemic blood flow. Systemic blood flow can be estimated by measuring flow in the superior vena cava (SVC). OBJECTIVE: To re-evaluate the accuracy of standard echocardiographic markers of ...

Theoretical arguments predict that the distribution of cold dark matter in spiral galaxies has peaks in velocity space associated with nonthermalized flows of dark matter particles. We searched for the corresponding peaks in the spectrum of microwave photons from axion to photon conversion in a cavity detector for dark matter ...

BACKGROUND AND PURPOSE: Migraine is considered a disorder of the autonomic nervous system. We used the frequency analysis of dynamic cerebral autoregulation to assess whether blood flow regulation disturbances can be found at the frequencies at which sympathetic and parasympathetic activity is present. METHODS: We measured simultaneously mean arterial blood ...

AIM: Pulsed Doppler ultrasound is a standard noninvasive investigation to measure the velocity and pulsatility of blood flow within the major intracranial and organ-supplying arteries in critical care patients. The normal arterial flow pattern in organ-supplying vessels is characterised by a systolic-diastolic forward flow which is caused by the aortic ...

We examine the effects of a periodically varying flow velocity on the standing- and traveling-wave patterns formed by the flow-distributed oscillation mechanism. In the kinematic (or diffusionless) limit, the phase fronts undergo a simple, spatiotemporally periodic longitudinal displacement. On the other hand, when the diffusion is significant, periodic modulation of ...

A review of cardiovascular clinical and research applications of MRI phase-contrast velocity imaging, also known as velocity mapping or flow imaging. Phase-contrast basic principles, advantages, limitations, common pitfalls and artefacts are described. It can measure many different aspects of the complicated blood flow in the heart and vessels: volume flow ...

Mechanical properties of human large arteries result from the interaction between blood pressure, wall distensibility and shear stress. Both the arterial diameter changes through the cardiac cycle (distension) and blood flow velocities can be noninvasively investigated through Doppler ultrasound approaches. Recently, an integrated system processing in real-time all the echo ...

The study presents normal reference intervals and ranges of "normal" side-to-side and day-to-day variability of ocular blood flow Doppler parameters. Peak-systolic (PSV), end-diastolic velocity (EDV) and impedance indices in the ophthalmic artery (OA), the central retinal artery (CRA) and the short posterior ciliary artery (SPCA) of both orbits were determined ...

In recent years, the utility industry has turned to baghouses as an alternative technology for particulate emission control from pulverized-coal-fired power plants. One of the more significant issues is to improve poor gas distribution that causes bag failures in baghouse operation. Bag failures during operation are almost impossible to prevent, ...

PURPOSE: To investigate the effect of retrobulbar anaesthesia on retrobulbar haemodynamics, colour Doppler imaging was performed. Furthermore, the additive effect of epinephrine was examined. METHOD: Forty-one patients (age 72.7+/-8.9; 22 f, 19 m) undergoing planned cataract surgery were included in a prospective study. Colour Doppler imaging was performed before and ...

OBJECTIVES: Volatile anesthetics are thought to impair cerebral autoregulation more than i.v. anesthetics. However, few comparative studies have been carried out in humans. The aim of our study was to evaluate the differences in cerebral hemodynamic changes after introduction of isoflurane (a volatile anesthetic) and propofol (an i.v. anesthetic). METHODS: ...

BACKGROUND: The purpose of the present study was to determine the effects of pars plana vitrectomy on retrobulbar haemodynamics in patients with proliferative diabetic retinopathy (PDR). METHODS: Colour Doppler imaging was used for measurement of blood flow velocities and resistive index of the ophthalmic artery (OA), posterior ciliary arteries (PCA) ...

OBJECTIVE: To determine blood flow patterns in the common carotid artery and external jugular vein in cows before and after sedation achieved by administration of xylazine hydrochloride. ANIMALS: 30 clinically normal Swiss Braunvieh cows. PROCEDURE: A 5.0-MHz sector transducer was used to examine the common carotid artery and external jugular ...

Coronary artery flow velocity during a short period of apnoea was investigated by transthoracic Doppler recording in 10 healthy men, aged 24-52. During breath holding for 29 +/- 6 s the oxygen saturation in the finger, measured by pulse oxymetry, decreased from 97.5 +/- 0.8 to 90.0 +/- 3.2% (P ...

Previous studies have used flowmeters in environments that are within the expectations of their published ranges. Electromagnetic flowmeters have a published range from 0.1 to 79.0 m/min, and impeller flowmeters have a published range from 1.2 to 61.0 m/min. Velocity-log data collected in five long-screened production wells in the Pleasant ...

OBJECTIVES: To construct reference ranges for serial measurements of the umbilical artery (UA) absolute blood flow velocities in the second half of pregnancy and to test the hypothesis that significant associations exist between UA velocities and placental volume blood flow assessed from umbilical vein blood flow velocities and diameter. METHODS: ...

INTRODUCTION: The aim of this study was to compare the measurements of vertebral artery (VA) systolic flow velocity and flow volume for diagnosis of vertebrobasilar insufficiency (VBI). MATERIAL AND METHODS: We examined 96 patients who were referred for evaluation of VBI. Net vertebral artery flow volume and mean systolic flow ...

Side-branches and curvatures in the arterial tree yield deviations from the axial oriented velocity. Velocity or volume flow estimates based on the assumption that flow is axially oriented are of limited value at these sites. This article evaluates information obtainable by using a multigate Doppler ultrasound (US) instrument used with ...

The use of transthoracic Doppler echocardiography (TTDE) to evaluate the patterns and technique of measuring of left atrial appendage (LAA) flow velocities in normal cats. Left atrial enlargement and dysfunction are characteristic features of feline cardiomyopathy that may cause blood stasis in the left atrium (LA). This low flow state ...

Assessment of cerebral blood flow velocities (CBFV) can be used as a non-invasive tool to evaluate specific drug effects, like caffeine (CAF), acetazolamide (AA) as well as cognition. Their influences on each others CBFV were evaluated in detail, using a randomized, double-blind, double-dummy, placebo-controlled three-fold cross-over study design in 18 ...

OBJECTIVE: Studies on lateralization of cerebral metabolism during Wisconsin Card Sorting Test (WCST), a well-known paradigm of category learning, have shown mixed results. Moreover, sorting dimension (number, color and shape) is a cofounder of laterality in WCST. Functional transcranial Doppler sonography (fTCD) has a high temporal resolution and allows the ...

Rizatriptan represents a major advance in the treatment of migraine attack: inhibition of peripheral trigeminal nerve and constriction of intracranial extracerebral blood vessels have been proposed as its main antimigraine mechanisms of action. Although many studies may suggest that rizatriptan causes highly selective vasoconstriction within intracranial extracerebral vessels (i.e., meningeal ...

Short-term cardiovascular responses to postural change from sitting to standing involve complex interactions between the autonomic nervous system, which regulates blood pressure, and cerebral autoregulation, which maintains cerebral perfusion. We present a mathematical model that can predict dynamic changes in beat-to-beat arterial blood pressure and middle cerebral artery blood flow ...

BACKGROUND AND PURPOSE: Transcranial Doppler (TCD) sonography is useful to evaluate intracranial arteries, however, interpretation of the TCD results in anterior cerebral artery (ACA) is difficult because of hypoplasia or aplasia. We try to define useful TCD indices and cut-off values to determine the variations of ACA. METHODS: Consecutive patients ...

Tissue Doppler imaging (TDI) patterns from the left atrial appendage (LAA) were evaluated by transesophageal echocardiography. Reproducible, characteristic triphasic or biphasic tissue velocities similar to Doppler flow of the LAA were obtained. Patient peak TDI velocities correlated well with flow and were measurable in atrial fibrillation. Patients with an embolic ...

This study describes how elderly subjects initiate gait, and step from a position of quiet stance. Based on scores from selected standardized tests subjects were placed in either a high (HFL) or low functional level (LFL) group and were asked to initiate gait, step onto a 10 cm high, 1.22 ...

Recently, open-type push-pull ventilation systems have been widely employed as effective substitutes for the conventional local exhaust ventilation system, and have prevailed at many welding workshops in Japan. In this study, the effect of the uniform velocity on carbon dioxide (CO2) shielding arc welding was examined by laboratory experiments. The ...