DEPTH DETERMINATION OF CHROMOPHORES IN HUMAN SKIN BY PULSED PHOTOTHERMAL RADIOMETRY

We report on the application of pulsed photothermal radiometry (PPTR) to determine the depth of in-vitro and in-vivo subsurface chromophores in biological materials. Measurements provided by PPTR in combination with a nonnegative constrained conjugate-gradient algorithm are used to determine the initial temperature distributior. in a biological mat erial immediately following pulsed laser irradiation. Within the exper imental error, chromophore depths (50-450 mu m) in 55 in-vitro collage n phantoms determined by PPTR and optical low-coherence reflectometry are equivalent. The depths of port-wine-stain blood vessels determined by PPTR correlate very well with their locations found by computer-as sisted microscopic observation of histologic sections. The mean blood- vessel depth deduced from PPTR and histologic observation is statistic ally indistinguishable (p > 0.94).