Combining two excitation wavelengths for pulsed photothermal profiling of hypervascular lesions in human skin

When pulsed photothermal radiometry (PPTR) is used for depth profiling of h ypervascular lesions in human skin, melanin absorption also heats the most superficial skin layer (epidermis). Determination of lesion depth may be di fficult when it lies close to the epidermaldermal junction, due to PPTR's l imited spatial resolution. To overcome this problem, we have developed an a pproximation technique, which uses two excitation wavelengths (585 and 600 nm) to separate the vascular and epidermal components of the PPTR signal. T his technique permits a noninvasive determination of lesion depth and epide rmal thickness in vivo, even when the two layers are in close physical prox imity to each other. Such information provides the physician with guidance in selecting the optimal parameters for laser therapy on an individual pati ent basis.