Blood Velocity (blood + velocity)

Distribution by Scientific Domains


Selected Abstracts


Blood velocity assessment using 3D bright-blood time-resolved magnetic resonance angiography

MAGNETIC RESONANCE IN MEDICINE, Issue 3 2006
Sylvain Miraux
Abstract Blood velocity is a functional parameter that is not easily assessed noninvasively, especially in small animals. A new noninvasive method that uses magnetic resonance angiography (MRA) to measure blood flows is proposed. This method is based on the time-of-flight (TOF) phenomenon. By initially suppressing the signal from the stationary spins in the area of interest, it is possible to sequentially visualize only the signal from the moving spins entering a given volume. With this method, 3D cine images of the blood flow can be generated by positive contrast, with unparalleled spatial (<200 ,m) and temporal resolutions (<10 ms/image). As a result, it is possible to measure flow in sinuous paths. The present method was applied in vivo to measure the blood velocity in mouse carotid arteries. Because of its robustness and simplicity of implementation, this method has numerous potential applications for fundamental studies in small animal models. Magn Reson Med, 2006. 2006 Wiley-Liss, Inc. [source]


Radial artery thrombosis, palmar arch systolic blood velocities, and chronic regional pain syndrome 1 following transradial cardiac catheterization

CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 4 2002
Thomas J. Papadimos MD
Abstract The transradial approach to cardiac catheterization is popular and safe, but prolonged, aggressive hemostatic compression at the access site may lead to vascular and/or neurologic complications, either transient or permanent. Rarely, chronic regional pain syndrome 1 (reflex sympathetic dystrophy) may occur. Cathet Cardiovasc Intervent 2002;57:537,540. 2002 Wiley-Liss, Inc. [source]


2154: Are all glaucoma drugs equally effective?

ACTA OPHTHALMOLOGICA, Issue 2010
L SCHMETTERER
Purpose It is only in the recent years that we have got evidence that reducing intraocular pressure (IOP) is beneficial in terms of preventing glaucoma progression in all types of glaucomatous disease. Nowadays we do have numerous data from large clinical outcomes trials clearly indicating that the lower the IOP the better the visual field preservation. There is, however, less data available comparing outcomes of different pharmacological regimen. Methods Only few head-to-head comparisons of two drugs that are equally effective in lowering IOP have been published. It is generally assumed that such trials would yield similar results in visual field preservation with both regimen. Looking into the literature there is, however, some evidence for the opposite. Results One clinical trial indicates that betaxolol may be superior to timolol in terms of visual field perservation. Another trial indicates that a combination of dorzolamide and timolol is assocaited with less visual field detoriation than a combination of brinzolamide and timolol. In this study the risk of disease progression was closely linked to low blood velocities in retrobulbar vessels. Conclusion In light of these results and the lessons we have learned from other fields there is a need for further studies comparing the outcomes of different antiglaucoma drugs head-to-head. Given that the pathophysiology of glaucoma is only poorly understood it can not generally be expected that all glaucoma drugs are equally effective in perserving visual fields. Commercial interest [source]


Twelve-hour reproducibility of retinal and optic nerve blood flow parameters in healthy individuals

ACTA OPHTHALMOLOGICA, Issue 8 2009
Alexandra Luksch
Abstract. Purpose:, The aim of the present study was to investigate the reproducibility and potential diurnal variation of optic nerve head and retinal blood flow parameters in healthy individuals over a period of 12 hr. Methods:, We measured optic nerve head and retinal blood flow parameters in 16 healthy male non-smoking individuals at five time-points during the day (08:00, 11:00, 14:00, 17:00 and 20:00 hr). Outcome parameters were perimacular white blood cell flux (as assessed with the blue field entoptic technique), blood velocities in retinal veins (as assessed with bi-directional laser Doppler velocimetry), retinal arterial and venous diameters (as assessed with the retinal vessel analyser), optic nerve head blood flow, volume and velocity (as assessed with single point and scanning laser Doppler flowmetry) and blood velocities in the central retinal artery (as assessed with colour Doppler imaging). The coefficient of variation and the maximum change from baseline in an individual were calculated for each outcome parameter. Results:, No diurnal variation in optic nerve head or retinal blood flow was observed with any of the techniques employed. Coefficients of variation were between 1.6% and 18.5% for all outcome parameters. The maximum change from baseline in an individual was much higher, ranging from 3.7% to 78.2%. Conclusion:, Our data indicate that in healthy individuals the selected techniques provide adequate reproducibility to be used in clinical studies. However, in patients with eye diseases and reduced vision the reproducibility may be considerably worse. [source]


Automated Volumetric Flow Quantification Using Angle-Corrected Color Doppler Image

ECHOCARDIOGRAPHY, Issue 5 2004
Beomjin Kim Ph.D.
We have developed a fully automated method for measuring volumetric blood flow with angle-corrected blood velocity from a color Doppler image. By computing the blood flow vector through a conduit, the angle of incidence between the direction of ultrasound beam and the direction of blood flow can be measured to correct the underestimated blood velocity. This correction immediately contributes to the improvement of measurement accuracy. The developed method also enhances the conduit identification procedure that is one of the most important factors affecting the accuracy of volumetric measurement. To evaluate the validity of the developed algorithm, experimental studies had been applied to 21 healthy subjects and 10 patients. Volumetric flows were measured from a color Doppler image of the left ventricular outflow track, which were compared with blood volumes that were measured by traditional pulsed-wave (PW)-Doppler technique. The mean stroke volume difference between two methods was ,0.45 11.7 (mean SD). The proposed algorithm is a viable method for determining blood flow volume in an automated fashion. (ECHOCARDIOGRAPHY, Volume 21, July 2004) [source]


The effect of hypoxia on pulmonary O2 uptake, leg blood flow and muscle deoxygenation during single-leg knee-extension exercise

EXPERIMENTAL PHYSIOLOGY, Issue 3 2004
Darren S. DeLorey
The effect of hypoxic breathing on pulmonary O2 uptake (VO2p), leg blood flow (LBF) and O2 delivery and deoxygenation of the vastus lateralis muscle was examined during constant-load single-leg knee-extension exercise. Seven subjects (24 4 years; mean s.d.) performed two transitions from unloaded to moderate-intensity exercise (21 W) under normoxic and hypoxic (PETO2= 60 mmHg) conditions. Breath-by-breath VO2p and beat-by-beat femoral artery mean blood velocity (MBV) were measured by mass spectrometer and volume turbine and Doppler ultrasound (VingMed, CFM 750), respectively. Deoxy-(HHb), oxy-, and total haemoglobin/myoglobin were measured continuously by near-infrared spectroscopy (NIRS; Hamamatsu NIRO-300). VO2p data were filtered and averaged to 5 s bins at 20, 40, 60, 120, 180 and 300 s. MBV data were filtered and averaged to 2 s bins (1 contraction cycle). LBF was calculated for each contraction cycle and averaged to 5 s bins at 20, 40, 60, 120, 180 and 300 s. VO2p was significantly lower in hypoxia throughout the period of 20, 40, 60 and 120 s of the exercise on-transient. LBF (l min,1) was approximately 35% higher (P > 0.05) in hypoxia during the on-transient and steady-state of KE exercise, resulting in a similar leg O2 delivery in hypoxia and normoxia. Local muscle deoxygenation (HHb) was similar in hypoxia and normoxia. These results suggest that factors other than O2 delivery, possibly the diffusion of O2, were responsible for the lower O2 uptake during the exercise on-transient in hypoxia. [source]


Descending thoracic aortic blood flow parameters during emergent surgery in anesthetized critically ill dogs

JOURNAL OF VETERINARY EMERGENCY AND CRITICAL CARE, Issue 4 2002
Richard J. Mills DVM
Abstract Objective: To explore the potential value of transesophageally-determined descending thoracic aortic blood flow parameters in critically ill dogs undergoing surgery. Design: Observational case series. Setting: Private small animal referral hospital. Animals: Ten anesthetized critically ill dogs that underwent emergent surgery. Interventions: Placement of the ultrasonic transesophageal probe. Measurements and main results: Transesophageally-determined descending thoracic aortic blood flow, stroke volume, blood velocity, blood acceleration, left ventricular ejection time interval, and heart rate parameters were recorded every minute. Systolic and mean arterial blood pressures were non-invasively determined and recorded at 1,5 minute intervals. The anesthetist and surgeon were blinded to the descending thoracic aortic blood flow parameters. All dogs received fluid challenges as part of their management, and 2 dogs received dopamine. The variability of the descending thoracic aortic blood flow parameters within each dog was greater than has been reported in non-critically ill anesthetized dogs. Consistent trends in descending thoracic aortic blood flow parameters after fluid challenges were not found. An escalating dopamine infusion was, however, accompanied by increasing aortic blood flow, stroke volume, acceleration, and peak velocity. Conclusions: Descending thoracic aortic blood flow parameters may eventually be useful for evaluating the responses to and suggesting the need for cardiovascular interventions during emergent surgeries in anesthetized critically ill canine patients. For this to occur, more experience with this technology will be required. [source]


Blood velocity assessment using 3D bright-blood time-resolved magnetic resonance angiography

MAGNETIC RESONANCE IN MEDICINE, Issue 3 2006
Sylvain Miraux
Abstract Blood velocity is a functional parameter that is not easily assessed noninvasively, especially in small animals. A new noninvasive method that uses magnetic resonance angiography (MRA) to measure blood flows is proposed. This method is based on the time-of-flight (TOF) phenomenon. By initially suppressing the signal from the stationary spins in the area of interest, it is possible to sequentially visualize only the signal from the moving spins entering a given volume. With this method, 3D cine images of the blood flow can be generated by positive contrast, with unparalleled spatial (<200 ,m) and temporal resolutions (<10 ms/image). As a result, it is possible to measure flow in sinuous paths. The present method was applied in vivo to measure the blood velocity in mouse carotid arteries. Because of its robustness and simplicity of implementation, this method has numerous potential applications for fundamental studies in small animal models. Magn Reson Med, 2006. 2006 Wiley-Liss, Inc. [source]


Rapid measurement of aortic wave velocity: In vivo evaluation

MAGNETIC RESONANCE IN MEDICINE, Issue 1 2001
Kenneth A. Kraft
Abstract A 1D MR sequence has been developed for determining aortic flow wave velocity (WV), a metric of arterial compliance, within a single cardiac cycle. Studies were carried out on the thoracic aortas of 10 normal volunteers. Correlative WV data were also acquired from each subject using a conventional phase-velocity 2D mapping technique. Aortic WV in this cohort was found to range from 411 to 714 cm/s and was highly correlated (R = 0.95) between the two methods. Peak blood velocity was also measured using both methods and found to agree closely. The reproducibility of WV measurements using the rapid 1D method averaged 7.6%, which is comparable or better than that achieved using existing noninvasive techniques. Magn Reson Med 46:95,102, 2001. 2001 Wiley-Liss, Inc. [source]


Blood Flow in Snake Infrared Organs: Response-Induced Changes in Individual Vessels

MICROCIRCULATION, Issue 2 2007
RICHARD C. GORIS
ABSTRACT Objective: In the past the microkinetics of blood flow in the infrared pit organs of pit vipers has been studied with Doppler flowmetry using various infrared stimuli such as a human hand or soldering iron at various distances, lasers of various wavelengths, etc. Quick-acting variations in blood flow were recorded, and interpreted as a cooling mechanism for avoiding afterimage in the infrared receptors. However, the Doppler measurements provided only the summation of blood flow in a number of vessels covered by the sensing probe, but did not give data on flow in individual vessels. Methods: In the present work the authors introduced into the bloodstream of Gloydius and Trimeresurus pit vipers fluorescent microspheres labeled with fluorescein isothiocyanate (FITC) contained in a solution of FITC-dextran in physiological saline. They observed the passage of the microspheres through individual pit organ vessels with a fluorescent microscope to which was attached a high-speed video camera and image intensifier. Output of the camera was recorded before, during, and after stimulus with a 810-nm diode laser. Recording was done at 250 frames/s on high-speed video apparatus and downloaded to a hard disk. Disk files were loaded into proprietary software and particles were tracked and average velocities calculated. The data were then tested for significance by ANOVA with post hoc tests. Results: A significant (p < .05) increase in blood velocity was found at the focal point of the stimulus laser, but not anywhere removed from this point. Proximal severing of the pit sensory nerves caused degeneration of the pit receptor terminals and abolished stimulus-induced blood flow changes, but did not affect normal blood flow. Conclusions: The authors conclude that the receptors themselves are directly and locally controlling the smooth muscle elements of the blood vessels, in response to heating of the receptors by infrared radiation. They speculate that the heavy vascularization constitutes a cooling system for the radiation-encoding receptors, and further that the agent of control may be a volatile neuromediator such as nitric oxide. [source]


Comparative velocity investigations in cerebral arteries and aneurysms: 3D phase-contrast MR angiography, laser Doppler velocimetry and computational fluid dynamics

NMR IN BIOMEDICINE, Issue 8 2009
Dorothea I. Hollnagel
Abstract In western populations, cerebral aneurysms develop in approximately 4% of humans and they involve the risk of rupture. Blood flow patterns are of interest for understanding the pathogenesis of the lesions and may eventually contribute to deciding on the most efficient treatment procedure for a specific patient. Velocity mapping with phase-contrast magnetic resonance angiography (PC-MRA) is a non-invasive method for performing in vivo measurements on blood velocity. Several hemodynamic properties can either be derived directly from these measurements or a flow field with all its parameters can be simulated on the basis of the measurements. For both approaches, the accuracy of the PC-MRA data and subsequent modeling must be validated. Therefore, a realistic transient flow field in a well-defined patient-specific silicone phantom was investigated. Velocity investigations with PC-MRA in a 3,Tesla MR scanner, laser Doppler velocimetry (LDV) and computational fluid dynamics (CFD) were performed in the same model under equal flow conditions and compared to each other. The results showed that PC-MRA was qualitatively similar to LDV and CFD, but showed notable quantitative differences, while LDV and CFD agreed well. The accuracy of velocity quantification by PC-MRA was best in straight artery regions with the measurement plane being perpendicular to the primary flow direction. The accuracy decreased in regions with disturbed flow and in cases where the measurement plane was not perpendicular to the primary flow. Due to these findings, it is appropriate to use PC-MRA as the inlet and outlet conditions for numerical simulations to calculate velocities and shear stresses in disturbed regions like aneurysms, rather than derive these values directly from the full PC-MRA measured velocity field. Copyright 2009 John Wiley & Sons, Ltd. [source]


The effect of graduated compression stockings on blood velocity in the deep venous system of the lower limb in the postnatal period

BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 10 2007
R Jamieson
Venous thromboembolism (VTE) is the leading cause of maternal mortality in the UK and is also a major cause of long-term morbidity. Recent UK national guidelines recommend thromboprophylaxis, which includes the use of graduated compression stockings (GCS), for high-risk women to reduce the risk of VTE in both the antenatal and postpartum period. This study of 17 women examined the effects of GCS on the deep venous system in the immediate postpartum period and found a statistically significant reduction in the diameter of the common femoral vein (CFV) (pre- versus post stocking diameter: mean 10.39 mm [SD 2.09] versus mean 9.69 mm [SD 1.99]) and an increase in the rate of blood velocity in the CFV (pre- versus post stocking velocity: mean 10.0 cm/s [SD 2.7] versus 13.9 cm/s [SD 4.2]) 30 minutes after application of thigh length GCS in women 1 or 2 days following a singleton vaginal delivery at term. This confirms reduction in venous stasis in the deep venous system in the immediate postpartum woman by the use of GCS, supporting their use in improving venous function in this context. [source]


Effect of systemic moxaverine on ocular blood flow in humans

ACTA OPHTHALMOLOGICA, Issue 7 2009
Hemma Resch
Abstract. Purpose:, A number of common eye diseases are associated with ocular perfusion abnormalities. The present study aimed to investigate whether systemically administered moxaverine improves ocular blood flow. Methods:, Sixteen healthy volunteers were studied in this randomized, double-masked, placebo-controlled, two-way crossover study. Moxaverine in a dose of 150 mg was administered i.v. Ocular haemodynamic parameters were measured before and after drug administration. Retinal arterial and venous diameters were measured with a retinal vessel analyser. Retinal blood velocity was assessed using laser Doppler velocimetry and choroidal and optic nerve head blood flow was measured with laser Doppler flowmetry. Results:, Moxaverine increased choroidal blood flow (22.6 27.9%), an effect which was significant versus placebo (p = 0.015). Red blood cell velocity in retinal veins tended to increase by 13.6 13.3% after infusion of moxaverine, but this effect was not significant compared with placebo (p = 0.25). In the optic nerve head moxaverine also tended to increase blood flow (11.8 12.7%), but, again, this effect was not significant versus placebo (p = 0.12). Neither moxaverine nor placebo had an effect on retinal arterial diameters. In retinal veins moxaverine tended to induce vasodilation (2.6 2.8%) and to increase blood flow (19.6 16.5%), but these effects were not significant (both p = 0.12). Conclusions:, The present study indicates an increase in choroidal blood flow after systemic infusion of a single dose of moxaverine in healthy subjects. Further studies are warranted to investigate whether these effects are also seen after longterm treatment in patients with ocular vascular disease. [source]


Effect of glaucoma and glaucoma risk factors on choroidal hemodynamics

ACTA OPHTHALMOLOGICA, Issue 2009
W ABOU SAMRA
Purpose a) to determine subfoveal choroidal hemodynamics in patients with primary open angle glaucoma (POAG) and patients with ocular hypertension (OH); b) to assess the effects of diabetes (DM), systemic hypertension (SHT) and myopia on subfoveal choroidal hemodynamics Methods Laser Doppler flowmetry (LDF) was used to determine the subfoveal choroidal blood velocity (ChBVel), volume (ChBVol), and flow (ChBF) in 1) patients with POAG (n=85) and patients with OHT (n=25); 2) patients with glaucoma risk factors which were further subdivided into three subgroups; DM (n=93), SHT (n=57) and myopia (n=29) respectively. Subjects with each risk factor were further subdivided into two subgroups (without and with POAG), 3) age matched healthy controls (n=100). Results All LDF parameters were significantly reduced in all groups of patients compared with age matched controls. No statistically significant differences in the LDF parameters among HTG, NTG and OHT subgroups were detected. No significant difference in the LDF parameters between the two subgroup of each risk factor (without and with POAG) was noted. The LDF data of glaucomatous patients with risk factors demonstrated a significant reduction of ChBF and an increase in resistance in comparison to glaucomatous patients without risk factors Conclusion Subfoveal choroidal LDF parameters are reduced in subjects with POAG, OHT and patients with glaucoma risk factors, such as DM, SHT (under antihypertensive therapy) and myopia when compared with age matched healthy controls. However, the role of these choroidal circulatory alterations in the development or progression of the glaucomatous optic neuropathy remains to be clarified. [source]