Capillary blood flow monitoring using laser speckle contrast analysis (LASCA)

Coherent light scattered from an ensemble of moving scatterers produces a t ime-varying speckle pattern. The intensity fluctuations observed in a singl e speckle tan be regarded either as a time-varying interference effect or a s a Doppler beating effect. Techniques based on each of these approaches ha ve been developed to analyze the fluctuations in an attempt to measure the velocities of the scatterers. Most of these methods measure the temporal st atistics of the intensity fluctuations in a single speckle, i.e., at a sing le point. If a map of the velocity distribution is required, some form of s canning must be introduced. One way of avoiding the need to scan is to make use of the spatial statistics of time-integrated speckle. This is the basi s of a technique, already described in the literature, called laser speckle contrast analysis (LASCA). In this article, we present a brief review of t he theory linking the intensity fluctuations to the velocity and of the var ious techniques that have been proposed to measure them. We then describe t he present configuration of our LASCA technique and describe some recent de velopments in our search for a real-time, noninvasive, full-held technique for visualizing capillary blood flow. (C) 1999 Society of Photo-Optical Ins trumentation Engineers. [S1083-3668(99)01802-8].