LASER-DOPPLER PERFUSION IMAGING OF SYNOVIAL TISSUES USING RED AND NEAR-INFRARED LASERS

A new laser Doppler perfusion imaging (LDI) system was evaluated by co mparing it with the well-established radiolabelled microsphere techniq ue for measuring blood flow in the rabbit knee point capsule. In this study two laser sources (635 and 835 nm) were compared at three scan s peeds (50, 10 and 4 ms/pixel). With blood flow to the rabbit hindlimb controlled via a peristaltic pump, the comparison of LDI and microsphe re measurement techniques yielded highly significant correlations for both laser sources (r = 0.9; p = 0.0001; 14 measurements in 7 animals) . Comparison of the three scan speeds demonstrated acceptable agreemen t without significant bias between measurement, suggesting that the in evitable narrowing of the bandwidth at the fastest scan speed does not cause significant deterioration of the signal. The flux values obtain ed with 635 and 835 nm laser sources were linearly related (r = 0.93, p = 0.0001; 66 measurements in 12 animals), although there was a small but significant bias for higher values with the 635-nm laser (mean ra tio of flux values 1.06, 95% confidence interval, 1.01-1.12). These re sults validate the use of LDI with either wavelength laser for the ass essment of joint capsule perfusion.