An Overview of Three Promising Mechanical, Optical, and Biochemical Engineering Approaches to Improve Selective Photothermolysis of Refractory Port Wine Stains

During the last three decades, several laser systems, ancillary technologies, and treatment modalities have been developed for the treatment of port wine stains (PWSs). However, approximately half of the PWS patient population responds suboptimally to laser treatment. Consequently, novel treatment modalities and therapeutic techniques/strategies are required to improve PWS treatment efficacy. This overview therefore focuses on three distinct experimental approaches for the optimization of PWS laser treatment. The approaches are addressed from the perspective of mechanical engineering (the use of local hypobaric pressure to induce vasodilation in the laser-irradiated dermal microcirculation), optical engineering (laser-speckle imaging of post-treatment flow in laser-treated PWS skin), and biochemical engineering (light- and heat-activatable liposomal drug delivery systems to enhance the extent of post-irradiation vascular occlusion)

Selection of optimal infrared detector for pulsed photothermal profiling of vascular lesions

Selection of infrared (IR) detector is a key consideration in designing an experimental setup for temperature depth profiling using pulsed photothermal radiometry (PPTR). In addition to common detector characteristics, such as the spectral response, detector noise, and response speed, application-specific details must be taken into account to ensure optimal system performance. When comparing detectors with different spectral responses, blackbody emission characteristics must be considered in terms of influence on radiometric signal amplitude, as well as on background shot noise. In PPTR, optical penetration depth of the sample in the acquisition spectral band is also an important factor, affecting the stability of the temperature profile reconstruction. Moreover, due to spectral variation of IR absorption coefficient in watery tissues, the acquisition band must be appropriately narrowed to ensure the validity of the customary approximation of a constant absorption coefficient value in signal analysis. This reduces the signal-to-noise ratio, adversely affecting the stability and quality of the temperature profile reconstruction. We present a performance analysis of PPTR depth profiling in human skin using commercially available IR detectors (InSb, HgCdTe), operating in different spectral bands. A measurement simulation example, involving a simple, hyper-Gaussian temperature profile, and realistic noise levels, illustrates their expected performance

Selecting optimal detector for temperature profiling in human skin using pulsed photothermal radiometry

We simulate temperature depth profiling in human skin using pulsed photothermal radiometry (PPTR). By taking into account blackbody emission characteristics, spectral variation of human skin IR absorption coefficient, detectivity of available radiation detectors, and shot noise, we compute realistic PPTR signals for a test temperature profile, representing a subsurface vascular lesion. Analysis of the reconstructed temperature profiles enables a performance comparison of quantum IR detectors utilizing different spectral acquisition bands. The results suggest that HgCdTe detector used in 6–10 $\mu$m spectral band performs better than an InSb detector used at 4–5 $\mu$m