Computational model to evaluate port wine stain depth profiling using pulsed photothermal radiometry

Abstract

We report on development of an optical-thermal model to evaluate the use of pulsed photothermal radiometry (PPTR) for depth profiling of port wine stain (PWS) skin. In the model, digitized histology sections of a PWS biopsy were used as the input skin geometry. Laser induced temperature profiles were reconstructed from simulated PPTR signals by applying an iterative, non-negatively constrained conjugate gradient algorithm. Accuracy of the following PWS skin characteristics extracted from the reconstructed profiles was determined: (1) average epidermal thickness (z(epi)), (2) maximum epidermal temperature rise (DeltaT(epi,max)), (3) depth of PWS upper boundary (z(PWS)), and (4) depth of maximum PWS temperature rise (z(PWS,max)). Comparison of the actual and reconstructed profiles from PPTR data revealed a good match for all four PWS skin characteristics. Results of this study indicate that PPTR is a viable approach for depth profiling of PWS skin.

Blood flow dynamics after laser therapy of port wine stain birthmarks

“…The wide range of treatment parameters used in this study (Table A1) highlights the need to establish an objective method to determine which treatment parameters to utilize on each patient. Several published studies [20][21][22] have shown that the treatment efficacy may have a strong dependence on individual PWS skin characteristics, such as vessel size, diameter, and depth. Hence, observation of regions of persistent perfusion may suggest that an alternate treatment protocol would target more effectively an individual patient's vasculature [23].…”

Three-dimensional Monte Carlo model of pulsed-laser treatment of cutaneous vascular lesions

“…Here, μ a,der is the absorption coefficient of bloodless dermis (0.053 mm − 1 at 532 nm), 14 and C i is the correction factor accounting for optical screening within a blood vessel of radius r i : 15,16 C i = 0.03895 + 0.48588 exp − μ a,bld r i 0.1928 The photon launching pattern simulates an incident laser beam with a top-hat profile (diameter: 5 mm) centered above the PWS blood vessel.…”

Selected Laser-based Therapies in Otolaryngology

“…PPTR measures the time-resolved changes in the blackbody emission of an object after irradiation with a laser pulse. PPTR has been applied by several groups for depth profiling of PWSs, but it also has some limitations [19]. As discussed earlier, light absorption dissipates as heat; thus, it increases the temperature and changes the blackbody emission spectrum.…”

“…The average success rate for complete blanching of PWS is less than 25% [19]. A major limitation of current laser therapy is that there are no objective criteria to guide treatment plans.…”

“…Knowledge of detailed skin parameters around the PWS and of the PWS itself could help optimize treatment. One recent article describes the development of a onedimensional computational model for PWS depth profiling using pulsed photothermal radiometry (PPTR) [19]. PPTR measures the time-resolved changes in the blackbody emission of an object after irradiation with a laser pulse.…”