Prediction of portwine stain clearance and required number of flashlamp pumped pulsed dye laser treatments

BACKGROUND AND OBJECTIVE: Portwine stain (PWS) response to flashlamp pumped pulsed dye laser (FPPDL) treatment is variable and unpredictable. Our aim was to develop a model to predict treatment outcome and the required number of treatments. STUDY DESIGN/MATERIALS AND METHODS: We hypothesized that PWS clearance decreases exponentially with the number of treatments, as a consequence of the exponential decrease of laser light fluence in human skin. Of 70 patients with a PWS in the head/neck area, the color difference between normal skin and PWS was measured with a chromameter, prior to, and at several stages during FPPDL treatment. Through the obtained values of each of the four color parameters, DeltaL*, Deltaa*, Deltab*, and DeltaE, mono-exponentially decreasing functions were fitted. RESULTS: All four color parameters showed decreasing exponential functions, with decay rates that were not significantly different, and a mean R(2) of 0.6, indicating a reliable fit-quality. CONCLUSIONS: Our model suggests that individual prediction of treatment outcome and the required number of treatments is possible in an early stage of FPPDL treatment of PWS, in theory already after one single laser treatment