Spectral density and tissue perfusion from speckle contrast measurements

Abstract

Progress in laser and camera technology has simplified the acquisition of laser speckle images relating to dermal blood flow. Using speckle contrast measurements over 5 decades of exposure time, we show that a temporal autocorrelation function, and hence spectral information and a perfusion index precisely equivalent to that produced in Doppler methods, can be derived from speckle measurements. The autocorrelation data are well approximated by a simple but nonexponential function which is parametric in a characteristic time τ_c. We suggest that the perfusion index could be found simply by determining τ_c from a small number of speckle measurements at appropriate exposures. This is illustrated by measurement of perfusion recovery following an induced change in perfusion.