DUPLEX LASER-DOPPLER PERFUSION IMAGING

A duplex mode for recording of both spatial and temporal blood perfusi on components has been developed and evaluated. This modality, which h as been implemented as a software module in the laser Doppler perfusio n imager, consists of various local area scan (LAS) configurations. Th ese include single-point recording or multipoint recording after repea ted movements of the laser beam in quadratic patterns including 2 x 2 or 4 x 4 measurement sites. For the 2 x 2 and 4 x 4 LAS, the output va lue constitutes the average perfusion of all values captured within th e actual region of interest. The 2 x 2 local area scan is corrected by time shifting the sequentially recorded measurement values at consecu tive tissue sites, while the 4 x 4 LAS is presented as a vector of the individual subimages. With the standard setting of 65 msec for the si gnal integration time at each measurement site, the 1 x 1 and 2 x 2 LA S configurations can capture and reproduce perfusion signals with maxi mal bandwidths of 7.7 and 1.9 Hz, respectively. System evaluation show ed that the signal integration time can be reduced to 45 msec without impaired signal quality, thereby further increasing the system bandwid th with a factor of about 1.5. Skin recordings showed that averaged ti me traces of adjacent measurement sires improve the signal-to-noise ra tio and allow for a more reliable analysis of, for example, the reacti ve hyperemic response. individual time-trace extraction, however, show ed reperfusion patterns that differed markedly between sites. (C) 1996 Academic Press, Inc.