Fiber Optical Spatial Filter Anemometry – Intravital Measurement of Red Blood Flow Velocity (RBCV) in the Microcirculation

Abstract

The fiberoptical spatial filter anemometry (SFA) is a common technique based on an optical grid to measure the velocity of corpuscular components in a multiphase flow, e.g. in the microvessels. The technical innovation is the analysis of flow velocities using an optical grid sensor and frequency analysis by Fast Fourier Transformation (FFT). This study describes a non-invasive, on-line technique to measure RBCV in the microcirculation. The sensor's validity was proven by in vitro measurements using a rotation disk of an exactly defined velocity with a correlation coefficient of 0.99967. For validation of RBCV measurements in the microcirculation in vivo, the setup was adapted to an intravital microscope. RBCV was measured in arterioles, capillaries, and postcapillary venules ranging from 8-140 microm diameter. As reference method for velocity measurements a computer assisted imaging system was used to measure the RBC-velocity in the identical vessels by frame to frame analysis. Both methods revealed a high significant correlation using transillumination technique for capillaries (r=0.986, p<0.001) and venules (r=0.952, p<0.001) as well as epiillumination technique (capillaries r=0.939, venules r=0.975, p<0.001).

Computer-assisted image analysis of agonist-mediated microvascular constriction response in mouse cremaster muscle

“…Analysis of microcirculatory blood flow in a rat cremaster muscle preparation using a cross-correlation algorithm has also been reported [ 14 ]. However, some limitations for these methods are the necessity to use fluorescent markers, the error caused by movements of the specimen or the requirement of good video images showing venules and arterioles with well-defined shapes and borders [ 14 , 30 ]. Simulations have been also used to analyze microcirculation.…”