<title>Laser speckle contrast analysis (LASCA): a real-time solution for monitoring capillary blood flow and velocity</title>

Abstract

To realize a non-contact, non-invasive and fast measurement of skin blood flow, we have developed the laser speckle contrast analysis (LASCA) technique. The LASCA method is a spatial domain method, based on the aggregate of pixels composing a captured laser speckle image. The contrast calculation operates directly on these pixels. In this paper, we present the computer algorithms to achieve a real-time solution for monitoring capillary blood flow and velocity. First, we present an improved naive LASCA algorithm with the running time O(k<SUP>2</SUP>n), where n is the total number of pixels and k X k represents the size of the subimage considered. Then, we describe a fast LASCA algorithm, which takes time O(kn) to calculate the local contrasts. Finally, we use the fast sequential algorithm to design the first LASCA parallel algorithm to run on the CREW PRAM with the running time O(k/p n), where p is the number of processors. Experimental result shows that, to process a laser speckle image with the size of 640 X 480, it takes only about one second using the fast LASCA algorithm. Furthermore, our parallel algorithm is easily implemented to run under the Windows NT environment by using multi-threads technique.