BACKGROUND AND PURPOSE: To study hemodynamic changes and to determine the value of contrast-enhanced transcranial color-coded sonography (TCCS) for the evaluation of dural arteriovenous fistulae (DAVF) before and after transcatheter embolization. METHODS: Twenty-four patients (mean age 61+/-11 years) with occipitally located DAVF were studied with contrast-enhanced TCCS using the transtemporal ...

This study shows that there is only a negligible difference in actomyosin function in the in vitro motility assay among actin filaments labeled with Rhodamine phalloidin (RhPh), Alexa-488 phalloidin (APh), and biotin-XX phalloidin (BPh). Similar results were obtained at varying ionic strengths (0.02-0.13 M), in the presence of imidazole or ...

BACKGROUND: CBFV (cerebral blood flow velocity) is lower in the morning than in the afternoon and evening. Two hypotheses have been proposed to explain the time of day changes in CBFV: 1) CBFV changes are due to sleep-associated processes or 2) time of day changes in CBFV are due to ...

Cerebral venous outflow abnormalities, as transverse sinuses (TSs) stenosis,may underlie a picture of idiopathic intracranial hypertension (IIH). To identify the best non-invasive MR venography (MRV) technique for exploring the disturbance of flow of TSs in IIH patients, we compared three dimensional phase contrast (3-DPC) MRV images, acquired with different velocity ...

We have developed a novel, non-intrusive fluid velocity measurement method based on photobleaching of a fluorescent dye for microfluidic devices. The residence time of the fluorescent dye in a laser beam depends on the flow velocity and approximately corresponds to the decaying time of the photobleaching of the dye in ...

BACKGROUND: Measure of blood flow velocity in retrobulbar vessels is performed to determine the severity of ophthalmic pathologies as glaucoma. In children, this measure is usually performed under general anaesthesia. Sevoflurane is known to not modify cerebral blow flow velocities. However, its effect on retrobulbar circulation is not known. This ...

OBJECTIVE: To determine possible effects of prolonged marijuana use on the cerebrovascular system during a month of monitored abstinence and to assess how the intensity of current use might have influenced cerebrovascular perfusion in these marijuana users. METHOD: The authors recorded blood flow velocity in the anterior and middle cerebral ...

OBJECTIVE: We aimed to prospectively investigate the predictive value of echocardiographic parameters for the prediction of successful cardioversion and long-term sinus rhythm (SR) maintenance in patients who have experienced a lone episode of atrial fibrillation (AF). MEASUREMENTS AND RESULTS: Clinical and echocardiographic data, including mean left atrial appendage (LAA) peak ...

The present study examined the rheological blood velocity profile in the conduit femoral artery during rhythmic muscle contractions at different muscle forces. Eight healthy volunteers performed one-legged, dynamic knee-extensor exercise at work rates of 5, 10, 20, 30, and 40 W at 60 contractions per minute. The time and space-averaged, ...

OBJECTIVE: To estimate variability of renal flow Doppler parameters during the menstrual cycle in young women, and to explore whether the parameters oscillate substantially throughout the cycle. METHODS: The peak systolic, mean, and end-diastolic velocities, pulsatility (PI) and resistance (RI) indices, acceleration time (AT) and index (AI) of the right ...

This paper proposes a new way for ultrasound color flow velocity estimation and display. This method sets up a mapping table which directly relates to the dynamic range of the velocity display by using an inverse mapping instead of calculating the arctangent value directly. This method is ideal for software ...

We evaluated three non-invasive method, thermography, laser Doppler imaging and near infrared multi-spectral imaging to quantitatively assess parameters of vascularity in Kaposi's sarcoma. The KS lesion generally has increased temperature, blood velocity and blood deoxy-hemoglobin. There is a strong correlation between temperature and blood velocity (R= 81, p <0.001). After ...

Respiratory tubes with the length of 35 mm and the diameters of 10, 15, and 20 mm were specially made and both the static(Ps) and dynamic (Pd) pressures were simultaneously measured for steady flow rates ranging 1-12 l/sec. Least squares analysis resulted successful fitting of Ps and Pd data with ...

A wide range of blood flow measurement techniques were reviewed in regard to development of an implantable blood flow sensor. These include indicator methods and techniques to measure velocity and stroke volume. Most techniques were found to be unsuitable for implantable use in humans. The intracardiac impedance method was favored, ...

To confirm the reliability of a refill kinetic method of ultrasonic harmonic perfusion imaging (HPI) capable of quantifying separate parameters of microvascular blood flow velocity and volume in brain tissue, we evaluated acetazolamide (ACZ) cerebrovascular reactivity by transcranial HPI in comparison with Doppler sonography (TCD). Methods. HPI during continuous Levovist ...

INTRODUCTION: Transcranial Dopplers (TCDs) have been used to monitor cerebral blood flow velocities in subarachnoid hemorrhage (SAH).The purpose of our two-part study was to compare the reliability of relative increases in flow velocities with conventionally used absolute flow velocity indices and to correct for hyperemia-induced flow velocity change. METHODS: Part ...

The impact of flow velocity (FV) on the growth dynamics of biofilms and bulk water heterotrophic plate count (HPC) bacteria in drinking water distribution systems was quantified and modeled by combining a logistic growth model with mass balance equations. The dynamic variations in the specific growth and release rates of ...

PURPOSE: To assess constant and pulsatile flow velocity within the lumen of a peripheral NiTi stent using phase velocity mapping for comparison with independent assessments of flow velocity in a phantom model. MATERIALS AND METHODS: A 9 x 20-mm stent installed in flexible tubing was placed in a phantom filled ...

PURPOSE: of the study was to evaluate blood flow in the arteries of the eye in preterm neonates. MATERIAL AND METHODS: Color Doppler imaging (CDI) of ophthalmic artery, central retinal artery and posterior ciliary arteries was performed in 36 preterm infants and 19 full-term infants. Maximal systolic velocity, end-diastolic velocity, ...

BACKGROUND: This study prospectively determined the haemodynamic changes in the lower limb venous circulation during and shortly after elective abdominal surgery, performed under general anaesthesia. METHODS: Ten females, aged 36-65 yr, ASA I or II, undergoing total abdominal hysterectomy had their peak, mean and minimum velocities, diameter, volume flow and ...

A MR method is presented for measuring pulse wave velocity (PWV) and its application to assessing stiffness in the human thoracic aorta. This one-dimensional (1D) flow displacement method applies a single RF comb excitation to the vessel, followed by an oscillating frequency encoding gradient, each oscillation providing a 1D projection ...

BACKGROUND: In premature infants, intraventricular hemorrhage occurs more commonly in the left than the right hemisphere. We have demonstrated previously that cerebral blood flow velocity is lower in the left than the right middle cerebral artery in the first few hours after birth. This may be due to the open ...

The subendocardium is the most vulnerable area of the left ventricle to the effects of hypoperfusion and ischemia. Despite this well-acknowledged observation, the mechanisms underlying this susceptibility are not elucidated, although numerous explanations including differences in transmural distribution of hemodynamics, metabolism, and wall stresses have been proposed. Our goal was ...

Real-time three-dimensional (3-D) color Doppler echocardiography (RT3D) is capable of quantifying flow. However, low temporal resolution limits its application to stroke volume (SV) measurements. The aim of the present study was, therefore, to develop a reliable method to quantify SV. In animal experiments, cross-sectional images of the LV outflow tract ...

The effect of spontaneous beat-to-beat mean arterial blood pressure fluctuations and breath-to-breath end-tidal CO2 fluctuations on beat-to-beat cerebral blood flow velocity variations is studied using the Laguerre-Volterra network methodology for multiple-input nonlinear systems. The observations made from experimental measurements from ten healthy human subjects reveal that, whereas pressure fluctuations explain ...

The global entropy generation rate in the zero-mean oscillatory flow of a Maxwell fluid in a pipe is analyzed with the aim of determining its behavior at resonant flow conditions. This quantity is calculated explicitly using the analytic expression for the velocity field and assuming isothermal conditions. The global entropy ...

In the present study cerebral blood flow was assessed in 40 subjects with chronically low blood pressure and 40 normotensive controls at resting conditions and during the execution of a cued reaction time task. Blood flow velocities were recorded by means of transcranial Doppler sonography in both middle cerebral arteries. ...

OBJECTIVE: Migraine-related dizziness can present with or without headache, often making diagnosis difficult. Flow velocity and CO 2 reactivity testing using transcranial Doppler (TCD) measurement of intracranial blood flow has been described as abnormal in patients with classic or common migraine. This study sought to determine the utility, if any, ...

PURPOSE: To evaluate the cerebral blood flow velocity in patients with ocular hypertension. MATERIAL AND METHODS: Twenty-four ocular hypertensive patients and 24 age- and sex-matched healthy volunteers were recruited in a prospective comparative study. All subjects had normal findings on full-threshold visual field tests and clinically normal optic nerves. All ...

BACKGROUND AND PURPOSE: Ischemic stroke occurs in at least 11% of patients with homozygous sickle cell anemia (SCD) by the time they turn 20 years old. High risk associated with distal intracranial internal carotid (ICA) and proximal middle cerebral artery (MCA) stenosis can be detected by transcranial Doppler (TCD). TCD ...

Ozone therapy is currently being used in the treatment of ischemic disorders, but the underlying mechanisms that result in successful treatment are not well known. This study assesses the effect of ozone therapy on the blood flow in the middle cerebral and common carotid arteries. Seven subjects were recruited for ...

OBJECTIVES: Cerebral hypoperfusion has been evidenced in patients with periventricular white matter lucency (PWML), however, our knowledge is limited regarding vasoreactivity (VR) changes in these patients. Therefore, we compared the cerebral blood flow velocity (CBFV) responses during different vasoregulatory challenges in healthy volunteers, to those in patients with PWML. MATERIAL ...

BACKGROUND AND PURPOSE: The intracarotid amobarbital procedure (IAP) leads to a prompt decrease in ipsilateral middle cerebral artery (MCA) mean blood flow velocity (MFV). Little is known about contralateral MFV changes. METHODS: The authors investigated bilateral MCA MFV using transcranial Doppler sonography (TCD) in 8 patients with epilepsy undergoing IAP. ...

OBJECTIVE: This study was undertaken to determine whether is there a difference in the middle cerebral artery peak systolic velocity (MCA PSV) between active and resting behavioral states in healthy fetuses aged 30 to 32 weeks. METHODS: MCA blood flow was measured by pulsed Doppler sonography 3 times during each ...

BACKGROUND AND PURPOSE: Although the diagnosis of moyamoya disease may be confirmed by digital subtraction angiography, recent studies have shown the accuracy of magnetic resonance angiography. Characteristics of transcranial Doppler, a noninvasive and cost-effective method, and specific transcranial Doppler parameters reflecting distinct vascular status in moyamoya disease are explored. METHOD ...

Finite time correlations of the velocity in a surface flow are found to be important for the formation of clusters of Lagrangian tracers. The degree of clustering characterized by the Lyapunov spectrum of the flow is numerically shown to be in qualitative agreement with the predictions for the white-in-time compressible ...

Flow measurements can be used to quantify blood flow during MR-guided intravascular interventional procedures. In this study, a fast flow measurement technique is proposed that quantifies flow velocities in the vicinity of a small RF coil attached to an intravascular catheter. Since the small RF coil receives signal from only ...

A method for flow estimation using synthetic aperture imaging and focusing along the flow direction is presented. The method can find the correct velocity magnitude for any flow angle, and full color flow images can be measured using only 32 to 128 pulse emissions. The approach uses spherical wave emissions ...

OBJECTIVES: The aim of this study was to determine the effect of electrical isolation of pulmonic vein (PV) on flow velocity. BACKGROUND: We report our experience with electrical isolation of PV by partial circumferential ablation and its effect on ostial peak flow velocity as assessed by phased-array ultrasound catheter imaging. ...

In this paper, the concept of open tubular traps, coated with a very thick film of polydimethyldisiloxane for enrichment of trace volatile components has been further explored. From theoretical calculations as well as practical experiments it is demonstrated that it can be advantageous to increase the inner diameter of such ...

Products of nanochemistry have been proposed in a number of applications ranging from soil stabilization and cosmetics to groundwater remediation. A fundamental understanding of the transport properties of these materials is essential to assess their efficacy and environmental impact in such applications. In this work, we consider the effect of ...

The rheology of a granular shear flow is studied in a quasi-2D rotating cylinder. Measurements are carried out near the midpoint along the length of the surface flowing layer where the flow is steady and nonaccelerating. Streakline photography and image analysis are used to obtain particle velocities and positions. Different ...

BACKGROUND: Mitral stenosis (MS) causes left atrial (LA) appendage (LAA) dysfunction resulting in reduced LAA flow velocities. Low LAA peak emptying velocity (PEV), determined by transesophageal echocardiography, is a risk for thrombus formation and systemic embolism. OBJECTIVE: We sought to investigate various clinical and echocardiographic predictors of low LAA blood ...

BACKGROUND: Cerebral vasomotor reactivity (CVR) is an index of cerebrovascular dilatory capacity which can readily be assessed using trans-cranial Doppler ultrasound. Impaired CVR is associated with elevated risk of stroke. We performed a randomized, double-blind placebo-controlled trial to investigate the effect of two HRT preparations upon CVR. METHODS: We examined ...

The purpose of this study was to estimate variability of flow Doppler parameters in the superior thyroid artery (STHA) during the menstrual cycle in young women and to explore the influence of endogenous 17-b-estradiol (E2) and progesterone (PRG) on the velocity waveform. The plasma concentration of these hormones was correlated ...

A computational model of the fluid dynamics of intraventricular flow was used to investigate the importance of the effects of flow disturbances existing within the left ventricle (LV) at the onset of diastole on a diastolic flow field. The simulation started with a quiescent flow state; it continued for a ...

Larval black flies often exhibit spatially aggregated distributions, and individuals within patches can potentially reduce the supply of suspended food particles to downstream neighbors by modifying local flow characteristics. We used hot-film anemometry to quantify the magnitude and spatial extent of flow modifications downstream from feeding Simulium vittatum larvae in ...

Phenotypic plasticity, the capacity of a given genotype to produce differing morphologies in response to the environment, is widespread among marine organisms (1). For example, acorn barnacles feed by extending specialized appendages (the cirral legs) into flow, and the length of the cirri is plastic: the higher the velocity, the ...

Cranioplasty can improve neurological status in patients with skull bone defects. The mechanism of postoperative improvement in neurologic status might be increased cerebral blood flow (CBF) velocity due to elimination of the effects of atmospheric pressure. Between May 2001 and June 2002, 13 patients (8 men and 5 women; average ...

INTRODUCTION: Application of radiofrequency energy at pulmonary vein (PV) ostium during focal atrial fibrillation (AF) ablation procedures increases flow velocity due to PV narrowing. Factors unrelated to ablation that effect PV flow velocity have not been described. AIMS OF THE STUDY: The purpose of this study was to evaluate, using ...