Search results for "velocimetry"
showing 10 items of 94 documents
Nicotinamide exerts different acute effects on microcirculatory function and tissue oxygenation in rat tumors
1993
Abstract Purpose : Nicotinamide has been reported to preferentially radiosensitize tumor tissue, supposedly through a reduction in tumor hypoxia. This may occur as a result of nicotinamide-induced changes in tumor blood flow and therefore the present study was undertaken to evaluate the effect of nicotinamide on circulatory parameters in skeletal muscle and tumor tissue (subcutaneously-implanted DS-sarcomas) of the rat. Methods and Materials : Mean arterial blood pressure (measured in the common carotid artery using a pressure transducer) and red blood cell flux (as measured by laser Doppler flowmetry) were continuously monitored for 120 min following a single intraperitoneal application of…
No improvement in perfusion and oxygenation of experimental tumors upon application of vasodilator drugs
2001
The oxygen deficiency seen in solid tumors is predominantly caused by an insufficient O2 supply as a result of inadequate tumor perfusion. The aim of this study was to analyze whether a number of vasodilator drugs might be suitable to increase tumor perfusion and consequently improve the oxygenation status of experimental tumors. Rats with s.c. DS-sarcomas were treated with either Na+-nitroprusside (7-25 microg x min(-1) x kg(-1) BW) or nifedipine (10 microg x min(-1) x kg(-1) BW). Red blood cell (RBC) flux was assessed continuously using laser-Doppler flowmetry and mean tumor pO2 was measured polarographically using O2-sensitive catheter electrodes. Systemic application of the vasodilator …
A Scanning Technique to Measure Regional Cerebral Blood Flow and Oxyhemoglobin Level
2001
OBJECTIVE: The application of a laser scanning technique to measure regional cerebral blood flow (CBF) and tissue hemoglobin oxygenation (HbO 2 ) using the rat closed cranial window preparation is described. METHODS: Twenty-nine male Wistar rats were used to consecutively measure local CBF by laser Doppler flowmetry and tissue HbO 2 by a microspectrophotometric method at multiple corresponding cortical locations. The scanning technique used a computer-controlled micromanipulator. Data from three experimental models are presented: the whisker stimulation model, the ischemia-reperfusion model, and the sinus-vein thrombosis model. Sequential changes in local CBF and HbO 2 data before, during, …
Cerebral blood flow alterations in a rat model of cerebral sinus thrombosis.
1993
Outcome from sinus vein thrombosis is very variable, with symptoms from headache to coma. Experimental findings suggest that an involvement of cortical veins is necessary to affect the cerebral microcirculation. Laser Doppler flowmetry was used to investigate the regional and temporal changes in local cortical blood flow after experimental occlusion and thrombosis of the superior sagittal sinus and tributary cortical veins in rats. Thrombosis was induced by slow injection of kaolin-cephalin suspension after frontal and caudal ligation of the sagittal sinus in rats. Local cerebral blood flow was measured by laser Doppler flowmetry and correlated with parenchymal damage found 24 hours after i…
Color Doppler Hemodynamics of Giant Cell Arteritis
1994
Objectives: To determine quantitative and qualitative hemodynamic alterations within the ophthalmic, central retinal, and short posterior ciliary arteries in patients with giant cell arteritis (GCA) proved by biopsy specimen. Design, Patients, and Setting: A consecutive case series of patients with GCA referred to an urban eye hospital who were evaluated with color Doppler imaging that was used to analyze orbital blood flow velocities and vascular resistance in 22 consecutive patients with GCA compared with age and sex-matched controls. Results: Patients with GCA all demonstrated significantly reduced central retinal and short posterior ciliary arterial mean flow velocities as well as signi…
Particle image velocimetry study of the celiac trunk hemodynamic induced by continuous-flow left ventricular assist device
2017
Abstract Whereas left ventricular assist device (LVAD) is the gold-standard therapy for patients with heart failure, gastrointestinal bleeding is one of the most common complications. LVAD implantation may remarkably impact aortic hemodynamics so that experimental and computational flow analyses can be used to study the disease mechanisms. Here we present an experimentally-calibrated computational model of the celiac trunk hemodynamic of a LVAD-supported patient who experienced bleeding after device implantation. Specifically, both particle image velocimetry (PIV) and echocardiography were used to measure and compare flow distributions in each branch of a phantom model of the patient abdomi…
Effects of hypertonic/hyperoncotic treatment after rat cortical vein occlusion*
2003
Objective To examine the effects of hypertonic/hyperoncotic treatment on physiologic variables and regional cerebral blood flow and to test its neuroprotective efficiency in a model of permanent venous ischemia. Design Randomized prospective study. Setting University research institute. Subjects Adult male Wistar rats, weighing 359 +/- 54 g (n = 38). Interventions Rats were subjected to photochemical occlusion of two adjacent cortical veins. A randomized infusion with vehicle (0.9% NaCl), 10% hydroxyethyl starch 200,000 (HES), or 7.5% saline plus 10% hydroxyethyl starch 200,000 (HHES) was started 30 mins after two-vein occlusion. Effects on physiologic variables and regional cerebral blood …
Cardiac kinematic parameters computed from video of in situ beating heart
2017
AbstractMechanical function of the heart during open-chest cardiac surgery is exclusively monitored by echocardiographic techniques. However, little is known about local kinematics, particularly for the reperfused regions after ischemic events. We report a novel imaging modality, which extracts local and global kinematic parameters from videos of in situ beating hearts, displaying live video cardiograms of the contraction events. A custom algorithm tracked the movement of a video marker positioned ad hoc onto a selected area and analyzed, during the entire recording, the contraction trajectory, displacement, velocity, acceleration, kinetic energy and force. Moreover, global epicardial veloc…
On the number of measurement sites required to assess regional cerebral blood flow by laser-Doppler scanning during cerebral ischemia and reperfusion.
2001
The aim of this study was to determine whether the number of measurement sites affected the precision of regional cerebral blood flow (CBF) assessment by Laser-Doppler (LD). A simulation study was applied based on data obtained by scanning the cortex in 25 rats during baseline conditions, 15 min global cerebral ischemia and reperfusion. Random samples were repeatedly collected from 1 to 100 locations and deviations from the median of the entire CBF data pool (800 locations) were determined. Single location CBF measurements missed the true median by 24.8+/-2.2 LD-units (baseline conditions, n=100 simulations, mean+/-SEM), 2.7+/-0.6 LD-units (ischemia), and 31.9+/-2.4 LD-units (30th min reper…
Capillary flow and diameter changes during reperfusion after global cerebral ischemia studied by intravital video microscopy.
2004
The reaction of cerebral capillaries to ischemia is unclear. Based on Hossmann's observation of postischemic “delayed hypoperfusion,” we hypothesized that capillary flow is decreased during reperfusion because of increased precapillary flow resistance. To test this hypothesis, we measured cerebral capillary erythrocyte velocity and diameter changes by intravital microscopy in gerbils. A cranial window was prepared over the frontoparietal cortex in 26 gerbils anesthetized with halothane. The animals underwent either a sham operation or fifteen minutes of bilateral carotid artery occlusion causing global cerebral ischemia. Capillary flow velocities were measured by frame-to-frame tracking of…