High speed perfusion imaging based on laser speckle fluctuations

Noninvasive methods to visualize blood flow in tissue are important in the clinical environment. Most methods use dynamic speckles to measure the level of perfusion. The most well-known techniques based on these speckle patterns are laser Doppler perfusion imaging (LDPI) and laser speckle contrast analysis (LASCA). For LASCA measurements an inexpensive camera which can achieve a frame-rate of 200 Hz is sufficient, whereas for LDPI, only a state-of-the-art high-speed camera which can achieve a frame-rate of about 25 kHz is suitable. A review of laser speckle contrast techniques so far, and a comparison of these techniques on the hand of a volunteer is given in chapter 2. In chapter 3 the Twente Optical Perfusion Camera (TOPCam), an imaging system based on high-speed CMOS technology is presented. The TOPCam was used to evaluate the capability and efficacy of the TOPCam to measure perfusion differences in burn wounds. In chapter 4 these first clinical results of the TOPCam in the setting of a burn centre are presented. In chapter 5, a Time Domain (TD) algorithm is presented for determining the first order spectral moment. This algorithm involves multiplications of an image with the difference between two subsequent images. The issue of the relation between the competing methods of laser Doppler perfusion imaging and laser speckle contrast methods is addressed in chapter 6. A theory is developed which expresses the contrast in time integrated dynamic speckle patterns in terms of the power spectral density of their local temporal intensity fluctuations.