Background/purposeDuring laser therapy of port wine stain (PWS) birthmarks in human skin, measurement of the epidermal temperature rise (DeltaT(epi)) is important to determine the maximal permissible light dose. In order to measure DeltaT(epi) on a specific PWS skin site, we developed an AC-coupled hand-held pulsed photothermal radiometry (PPTR) system, which overcomes the in vivo measurement limitations of bench-top systems.MethodsThe developed hand-held PPTR system consists of an infrared (IR) lens, AC-coupled thermoelectrically cooled IR detector, laser hand-piece holder, and positioning aperture. The raw AC-coupled signal was integrated to obtain a higher signal-to-noise ratio (SNR). The experimental temperature difference (DeltaT) calibration was compared with theoretical computations. In vitro and in vivo measurements of DeltaT were performed with a tissue phantom as a function of radiant exposure and human subject as a function of melanin concentration, respectively.ResultsThe integrated AC-coupled signal provided higher SNR as compared with the raw AC-coupled signal. The experimental DeltaT calibration resulted in good agreements with the theoretical results. The in vitro and in vivo results also presented good agreements with theory.ConclusionsA fiber-free, hand-held AC-coupled PPTR system is capable of accurate epidermis temperature rise (DeltaT(epi)) measurements of human skin during pulsed laser exposure
