Abstract

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 distribution in a biological material immediately following pulsed laser irradiation. Within the experimental error, chromophore depths (50-450 µm) in 55 in-vitro collagen 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-assisted microscopic observation of histologic sections. The mean blood-vessel depth deduced from PPTR and histologic observation is statistically indistinguishable (p > 0.94).

Highlights

  • In recent years, a number of investigators have studied various techniques to image the internal structure of human skin.[1,2,3] Many of these studies have been motivated by efforts to improve diagnosis and treatment of various skin pathologies

  • Pulsed photothermal radiometry 1PPTR2 is a noncontact technique that utilizes an infrared detector to measure temperature changes induced in a test material exposed to pulsed radiation

  • Heat generated as a result of light absorption by subsurface chromophores in the test material diffuses to the

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Summary

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Depth determination of chromophores in human skin by pulsed photothermal radiometry. We report on the application of pulsed photothermal radiometry 1PPTR2 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 distribution in a biological material immediately following pulsed laser irradiation. Chromophore depths 150–450 μm[2] in 55 in-vitro collagen 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-assisted microscopic observation of histologic sections. The mean blood-vessel depth deduced from PPTR and histologic observation is statistically indistinguishable 1 p . The mean blood-vessel depth deduced from PPTR and histologic observation is statistically indistinguishable 1 p . 0.942

Introduction
Methods and Materials
Results and Discussion
For each biopsied skin site a normalized thermal

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