Experimental estimation of blood flow velocity through simulation of intravital microscopic imaging in micro-vessels by different image processing methods.

Quantization of red blood cell (RBC) velocity in micro-vessel is one of the techniques for dynamic observation of microvascular mechanisms. The flow measurement of RBC in micro-vessels is still a challenge nowadays. Image processing for velocity measurement using a frame by frame analysis is a common approach. The accuracy of the calculations, which is algorithm dependant, has rarely been examined. In this paper, we evaluated the accuracy of the existing methods, which includes cross correlation method, Hough transform method, and optical flow method, by applying these methods to simulated micro-vessel image sequences. Simulated experiments in various micro-vessels with random RBC motion were applied in the evaluation. The blood flow variation in the same micro-vessels with different RBC densities and velocities was considered in the simulations. The calculation accuracy of different flow patterns and vessel shapes were also examined, respectively. Based on the comparison, the use of an optical flow method, which is superior to a cross-correlation method or a Hough transform method, is proposed for measuring RBC velocity. The study indicated that the optical flow method is suitable for accurately measuring the velocity of the RBCs in small or large micro-vessels.