Connecting laser Doppler perfusion imaging and laser speckle contrast analysis

Abstract

Laser Speckle Contrast Analysis (LASCA) and Laser Doppler Perfusion Imaging (LDPI) are techniques widely used for determining cerebral blood flow, the skin perfusion in burns and during drug uptake, and cerebral blood flow. Both techniques are based on the dynamic speckle pattern on the detector generated by the sample under investigation. In LASCA the speckle pattern is recorded using a long exposure time (i.e. milliseconds) resulting in a blurred image, the perfusion map is obtained by calculating the contrast in the blurred image over small areas (e.g. 5x5 or 7x7 pixels). In LDPI a series of speckle patterns are recorded using a short integration time (i.e. microseconds). By determining the power spectrum of the intensity fluctuations per pixel and calculating the first moment, the perfusion map is obtained. Because both techniques are based on the same phenomenon we show it is possible to relate the outputs of LASCA and LDPI. Such a connection is important because of the growing interest in LASCA techniques. Here we perform the first steps in the comparison of both techniques, using both simulated signals and signals measured with a high speed camera which can perform LDPI as well as LASCA.