Theoretical evaluation of pulsed photothermal radiometry (PPTR) for depth profiling of port wine stain skin

摘要

The purpose of this study was to evaluate the ability of single and dual wavelength excitation pulsed photothermal radiometry (SWE- and DWE-PPTR, respectively) to profile port wine stain (PWS) skin. To this end, a numerical optical-thermal model was developed, incorporating a digitized PWS biopsy as the input skin geometry. Both SWE and DWE reconstructed depth profiles were obtained by applying an iterative, nonnegatively constrained conjugate gradient algorithm to the computed PPTR signals. The accuracy of determining the following clinically significant parameters from our reconstructions was determined: 1) average epidermal thickness (z_(epi)), 2) maximum epidermal temperature rise (ΔT_(epi,max)), 3) initial PWS depth (z_(PWS)), and 4) depth of maximum PWS temperature rise (z_(PWS,max)). In the SWE-PPTR reconstruction, key parameters such as z_(epi) and z_(PWS) could not be determined. Comparison of the epidermal profiles of the actual and DWE-PPTR profiles revealed a good quantitative match in z_(epi) and ΔT_(epi,max). Comparison of the PWS profiles revealed that z_(PWS) and z_(PWS,max) are determined within 25% and 11%, respectively. The results of this study indicate that DWE-PPTR is a viable tool for depth profiling of PWS skin.