Blood Flow Velocity Measurement in Microcirculation Field by Means of Highly Accurate Iterative PIV.

Particle image velocimetry (PIV) has been the quantitative measurement method of instantaneous velocity fields in experimental fluid mechanics. The authors have proposed the adaptive PIV technique using the gradient-based sub-pixel analysis, in which a pixel unit displacement is obtained using the iterative cross-correlation method while a sub-pixel displacement is calculated by the use of the so-called spatio-temporal derivative method. The present method can achieve high accuracy of measurement and high spatial resolution compatibly. In this paper, the proposed method is applied to visualized images of the arteriole in the rat mesentery using the intravital-microscope and the high-speed digital video system. Time-series of the volocity profiles of the arteriole is obtained. Averaged velocity profiles show the blood flow volume is constant at five vessel cross-sections. The arteriole velocity profiles are blunt at the center region of the vessel cross-section and sharp profiles at near wall region, this suggests the shear stress on the vessel wall is higher than expected one. The results show that the proposed method is very useful to measure the blood flow velocity profiles with highly accuracy of measurement, and high temporal and spatial resolution.