Performance evaluation of pulsed photothermal profiling of port wine stain in human skin

Bincheng Li,Boris Majaron,Thomas E Milner,J Stuart Nelson,John A Viator

doi:10.1063/1.1753671

Abstract

Treatment of port wine stain (PWS) birthmarks in human skin by pulsed laser irradiation requires the knowledge of the maximum epidermal temperature rise and PWS depth for an attending physician to select the optimal light dosage, irradiation wavelength, and cryogen spray cooling spurt duration on an individual patient basis. Pulsed photothermal radiometry (PPTR) is a promising technique to provide such information. In this article, computer simulations are performed to evaluate the performance of PPTR depth profiling of the laser-induced temperature rise in PWS. An iterative, non-negatively constrained conjugate gradient algorithm is used to reconstruct the laser-induced temperature profile from simulated PPTR signals. Human skin is assumed to contain an epidermal melanin layer and a single homogeneous PWS layer in the dermis. The influence of structural, experimental, and algorithm parameters on the temperature profile reconstruction are discussed. Accuracy of the maximum epidermal temperature rise and PWS depth determined from the reconstructed profiles is statistically analyzed. The simulations show that when the melanin and PWS layers are physically discrete, a good reconstruction can be obtained and the maximum epidermal temperature rise and PWS depth can be determined with accuracy sufficient for the intended clinical application. Measurements and reconstructions from PWS patients are performed and the results are in agreement with the simulations.

Highlights

The present study addresses the accuracy of maximum epidermal temperature rise and PWS depth determination using PPTR depth profiling in presence of an epidermal melanin layer
Since PWS depth varies on an individual patient basis,[1–4] we investigate how PWS depth affects the reconstruction
For optimal depth profile reconstructions, the frame rate must be high, providing the required spatial resolution, yet selected to yield PPTR signals with a suitably high SNR and acquisition periods long enough to detect the radiometric signal from deeper parts of the object

Summary

Introduction

595 nmproduces a complete fading of PWS only in a selected population of patients.[6]. We believe that this happens primarily because of the inability of the physician to select optimal treatment parameters on an individual patient basis. Selection of treatment parameters for each patient should be based on determination of: ͑1͒ maximum epidermal temperature rise immediately after laser irradiation due to melanin absorption; and2͒ PWS depth. Knowledge of the maximum epidermal temperature rise allows the physician to determine the maximal light dosage for PWS destruction while avoiding epidermal damage. Knowledge of PWS depth is needed to determine the optimal irradiation wavelength and cryogen spray coolingCSCspurt duration applied prior to laser irradiation. CSC selectively cools and protects the epidermis from thermal damage[7,8] and has increased the therapeutic efficacy of PWS laser treatment.[8,9] in order to maximize the benefit of CSC, determination of the optimal spurt duration and delay between the spurt and laser pulse

Methods

Results

Conclusion