The application of pulsed photothermal radiometry (PPTR) diagnostics to characterize port wine stain (PWS) lesions is discussed. Influence of epidermal absorbance and PWS depth on the PPTR signal is analyzed using an in-vitro model of PWS skin consisting of multilayered collagen films. An instrument is constructed and used for patient and animal model PPTR measurements. When an infrared fiber is incorporated, the instrumentation facilitates convenient skin-site accessibility. Modulation of the PPTR signal and homodyne detection substantially improve the system signal-to-noise ratio over previous methods. Given the measured PPTR signal, an algorithm computes the initial temperature distribution in the PWS skin immediately after the laser pulse. The use and limitations of the algorithm are presented and discussed.

The application of pulsed photothermal radiometry (PPTR) diagnostics to characterize port wine stain (PWS) lesions is discussed. A PPTR signal of a PWS in response to pulsed laser exposure is shown to consist of an initial `T-jump' due to epidermal melanin absorption and a `delayed thermal wave' resulting from laser generated heat in subsurface blood vessels diffusing to the skin surface. A prototype PPTR instrument incorporating an infrared fiber is constructed which facilitates convenient skin-site accessibility. Laser heating of the infrared collection optics results in an artifactual signal which overestimates the initial `T-jump.' Magnitude of the error is measured and a method to eliminate it is suggested.

Photothermal tomography (PU) is applied to characterize diameter and depth of subcutaneous chromophores such as blood vessels that comprise port wine stain (PWS) birthmarks. PU uses a fast infrared detector array to measure temperature rises in a PWS induced by pulsed laser radiation. A FIT record of PWS in response to pulsed laser exposure is composed of a sequence of infrared emission frames, each consisting of elevated temperature regions indicative of subcutaneous blood vessel heating. An analytic expression for recorded infrared emission frames is derived as a convolution integral of a PTF point spread function and the three dimensional temperature distribution in the PWS immediately following laser exposure. Diameters of blood vessels comprising the PWS are best resolved in early infrared emission frames when radial heat diffusion is relatively small. Blood vessel images in subsequent frames increase in amplitude due to heat generated in the subsurface PWS diffusing to the skin surface indicative of a "delayed thermal wave". Influence of diameter and depth of blood vessels on the FVF record is analyzed using an in-vitro PWS model consisting of multilayered collagen films.