In vivo whole-field blood velocity measurement techniques

Abstract

In this article a number of whole-field blood velocity measurement techniques are concisely reviewed. We primarily focus on optical measurement techniques for in vivo applications, such as laser Doppler velocimetry (including time varying speckle), laser speckle contrast imaging and particle image velocimetry (including particle tracking). We also briefly describe nuclear magnetic resonance and ultrasound particle image velocimetry, two techniques that do not rely on optical access, but that are of importance to in vivo whole-field blood velocity measurement. Typical applications for whole-field methods are perfusion monitoring, the investigation of instantaneous blood flow patterns, the derivation of endothelial shear stress distributions from velocity fields, and the measurement of blood volume flow rates. These applications require individual treatment in terms of spatial and temporal resolution and number of measured velocity components. The requirements further differ for the investigation of macro-, meso-, and microscale blood flows. In this review we describe and classify those requirements and present techniques that satisfy them.

Laser Doppler imaging for intraoperative human brain mapping

“…These techniques range from fMRI, PET and Laser speckle imaging to optical intrinsic signal imaging and near-infrared spectroscopy amongst others (Hillman, 2007;Obrig and Villringer, 2003;Toga and Mazziotta, 2002;Vennemann et al, 2007). Each technique adds its portion of information to the puzzle but also brings with it its own specific technical limitations.…”

Multi-scale interaction of particulate flow and the artery wall

“…Multi-scale, multi-physics cardiac modelling has also been undertaken by Liu It is candidly admitted that ultrasound and MRI cannot measure velocities closer to the wall than 250-300 and 1000-1200 micrometres respectively (47), which range fails to resolve the glycocalyx (with, recall, characteristic thickness ≈ ). Ultrasonics, therefore, cannot answer a fundamental question as to whether ECs are not seeing WSS' (47) or are 'protected against high flow shear rates that may rupture the cells' (49). While CFD models can give good macroscopic comparisons with in vivo data (for example, 34) they are completely unable to address these issues.…”

‘Go with the flow ’: A review of methods and advancements in blood flow imaging

“…In addition to gleaning structural data, vascular imaging enables the quantification of blood vessel spacing, the assessment of blood flow and permeability [2,3], and the analysis of cellular and molecular abnormalities, and vessel wall shear stresses [4]. Structural and functional parameters may be elucidated by methods ranging from fluorescence to confocal and multiphoton microscopy.…”