Blood Flow Velocity In Vessels Research Articles

Substantiation of pharmacological correction of the condition of the ocular surface in postcovid syndrome

Substantiation of pharmacological correction of the condition of the ocular surface in postcovid syndrome

Divergence Compensatory Optical Flow Method for Blood Velocimetry

Detailed blood velocity map in the vascular system can be obtained by applying the optical flow method (OFM) in processing fluoroscopic digital subtracted catheter angiographic images; however, there are still challenges with the accuracy of this method. In the present study, a divergence compensatory optical flow method (DC-OFM), in which a nonzero divergence of velocity is assumed due to the finite resolution of the image, was explored and applied to the digital subtraction angiography (DSA) images of blood flow. The objective of this study is to examine the applicability and evaluate the accuracy of DC-OFM in assessing the blood flow velocity in vessels. First, an Oseen vortex flow was simulated on the standard particle image to generate an image pair. Then, the DC-OFM was applied on the particle image pair to recover the velocity field for validation. Second, DSA images of intracranial arteries were used to examine the accuracy of the current method. For each set of images, the first image is the in vivo DSA image, and the second image is generated by superimposing a given flow field. The recovered velocity map by DC-OFM agrees well with the exact velocity for both the particle images and the angiographic images. In comparison with the traditional OFM, the present method can provide more accurate velocity estimation. The accuracy of the velocity estimation can also be improved by implementing preprocess techniques including image intensification, Gaussian filtering, and "image-shift."

Determination of blood flow velocity in vessels of the bulbar conjunctiva

Determination of blood flow velocity in vessels of the bulbar conjunctiva

Monitoring of drug and stimulation induced cerebral blood flow velocity changes in rat sensory cortex using spectral domain Doppler optical coherence tomography

Doppler optical coherence tomography (DOCT) provides a novel method to measure blood flow velocity in vessels with diameter at micrometer scale. In this study, a developed spectral domain DOCT system is applied to monitor cerebral blood flow velocity changes in a rat. An animal model with a cranial window is used, and by application of a drug, light, and electric stimulations, changes in blood flow velocity of the pial artery in sensory cortex are measured in real time. The results show significant differences in blood flow velocity before and after drug administration or light and electric stimulations, demonstrating the feasibility of DOCT in cerebral microcirculation study. Given its noninvasive nature, high spatial resolution, high velocity sensitivity, and high imaging speed, DOCT shows great promise in brain research by imaging blood flow changes at micrometer scale vessels, which helps to understand the pathogenesis of cerebral diseases and neurodegenerative diseases.

Analysis of in vitro and in vivo bidirectional flow velocities by phase-resolved Doppler Fourier-domain OCT

Fourier-domain optical coherence tomography (FD-OCT) is a non-invasive imaging technique which allows the in vivo examination of subsurface tissue. Besides the structural imaging, FD-OCT is capable to measure blood flow velocities. This method is referred to as phase-resolved Doppler FD-OCT and often used in small retinal vessels (diameters about 100 μm) with low blood flow velocities. In this study, we present a FD-OCT system with a spectrum read-out rate of 11.88 kHz showing the ability to assess velocity profiles in the in vivo mouse model with blood vessels up to a diameter of 300 μm. Before realization of the in vivo study on such large vessels, an in vitro flow phantom using a 1% Intralipid solution as well as whole human blood flowing through a 320 μm glass capillary was constructed. The velocity profiles of the Intralipid flow can be measured entirely. Due to the large diameters of the capillary and the investigated murine vessels, entire flow profiles cannot be measured when using whole blood. But the flow can be estimated by fitting a parabolic velocity profile to the onset of the measured data. With this method, it is possible to analyze the systolic and diastolic arterial as well as the venous blood flow. To our knowledge this was the first time that blood flow velocities of vessels with inner diameters of about 300 μm in the in vivo mouse model were assessed by phase-resolved Doppler FD-OCT.

Study on cerebral microcirculation by Optical Doppler Tomography

Optical Doppler Tomography (ODT) provides a novel method to measure the blood flow velocity in vessels with the diameter at micrometer scale. Rats with cranial window are used as a model, and the changes in the blood flow velocity of cerebral arterioles in sensory cortex are measured in real time with an established ODT system, under electrical stimulation and drug administration. The results show significant differences in the blood flow velocity between experimental groups and control groups, demonstrating the feasibility of ODT in the cerebral microcirculation study. Compared with the conventional Doppler ultrasound, ODT provides much higher spatial resolution, and thus holds a promising future in the application of the cerebral microcirculation study, especially in the observation of the blood flow velocity in micrometer scale vessels.

Alterations in regional cerebral blood flow in neonatal stroke: preliminary findings with color Doppler sonography.

Little information is available regarding alterations in regional cerebral blood flow and vascularity on cranial sonography in infants with focal ischemic brain injury. This study describes the use of color Doppler sonography in the characterization of these changes following acute neonatal stroke. Color Doppler examinations were performed as part of the series of clinically indicated cranial sonograms in eight infants with clinical, sonographic, and CT evidence of acute cerebral infarction. The cerebral vascularity of each hemisphere was assessed for symmetry and for presence of abnormal blood vessels. Initial Doppler study in four infants with hypoxic-ischemic infarcts showed increased size and number of visible vessels in the periphery of the infarct and increased mean blood flow velocity in vessels supplying or draining the infarcted areas. Diminished vessel number and size and frequency shifts suggestive of decreased hemispheric perfusion was identified in one infant with middle cerebral artery insufficiency. Repeat Doppler studies were performed on two infants. These showed the development of multiple small, irregular blood vessels in the periphery of the infarct. Focal abnormalities in regional cerebral blood flow may be present as part of the normal healing process following neonatal stroke, and can be demonstrated with color Doppler sonography.