Fast and robust extraction of optical and morphological properties of human skin using a hybrid stochastic-deterministic algorithm: Monte-Carlo simulation study.

A hybrid deterministic-stochastic algorithm combining the simplex method (SM) and a genetic algorithm (GA) was applied to the problem of extracting the optical and morphological properties of human skin (HSOMPs) from visual reflectance spectroscopy data. The results using the GA-SM hybrid algorithm adopting tournament selection and selecting new sets of HSOMPs were compared with those using other conventional optimization algorithms that have generally been used for the extraction of HSOMPs. Monte-Carlo simulation showed that the suggested GA-SM hybrid algorithm enhanced the stability of the inverse solutions and computational efficiency.

Blood flow dynamics after laser therapy of port wine stain birthmarks.

BACKGROUND AND OBJECTIVE: During laser therapy of port wine stain (PWS) birthmarks, regions of perfusion may persist. We hypothesize that such regions are not readily observable even when laser surgery is performed by highly experienced clinicians. The objective of this study was to use objective feedback to assess the acute vascular response to laser therapy. STUDY DESIGN/MATERIALS AND METHODS: A clinic-friendly laser speckle imaging (LSI) instrument was developed to provide the clinician with real-time images of blood flow during laser therapy. Images were acquired from patients undergoing laser therapy of PWS birthmarks at Scripps Clinic and the Beckman Laser Institute and Medical Clinic. Blood flow maps were extracted from the acquired imaging data. Histogram-based analysis was applied in grading the degree of heterogeneity present in the blood flow maps after laser therapy. RESULTS: Collectively, two types of patient responses were observed in response to laser exposure: (1) an immediate increase in perfusion within minutes after laser therapy; and (2) an overall decrease in blood perfusion approximately 1 hour after laser therapy, with distinct regions of persistent perfusion apparent in the majority of post-treatment blood-flow images. A comparison of blood flow in PWS and adjacent normal skin demonstrated that PWS blood flow can be greater than, or sometimes equivalent to, that of normal skin. CONCLUSION: In general, a decrease in skin perfusion is observed during pulsed laser therapy of PWS birthmarks. However, a heterogeneous perfusion map was frequently observed. These regions of persistent perfusion may be due to incomplete photocoagulation of the targeted vessels. We hypothesize that immediate retreatment of these regions identified with LSI, will result in enhanced removal of the PWS vasculature. Lasers Surg. Med. 41:563-571, 2009. (c) 2009 Wiley-Liss, Inc.

Láser y otras fuentes de luz en el tratamiento de manchas en vino de Oporto / Laser treatment of Port wine stain

El tratamiento con láser de lesiones vasculares cutáneas está avanzando rápidamente en los últimos años. La mancha en vino de Oporto (Port wine stain [PWS]) es una de las primeras lesiones tratadas con láser con éxito. El láser de colorante pulsado (PDL) se ha desarrollado basándose en el concepto de la fototermólisis selectiva y ha supuesto una revolución en el tratamiento de PWS. Sin embargo, la respuesta obtenida es variable, alcanzándose un aclaramiento sustancial del color de la lesión tras varias sesiones. Diversos estudios demuestran que la modificación de parámetros del PDL como el aumento en la amplitud de pulso, mayor longitud de onda, o fluencias más altas asociadas a un sistema de enfriamiento, consiguen un aumento en la selectividad y mejoran la respuesta. Por otra parte, lesiones profundas, gruesas o sobreelevadas responden pobremente a los tratamientos convencionales. El objetivo de nuestro estudio es la revisión de los distintos tipos de láser así como otras fuentes de luz que se están desarrollando para el tratamiento de éstas y otras lesiones vasculares

Laser treatment of vascular skin lesions is rapidly improving. Port wine stain (PWS) is one of the first lesions successfully treated with laser. The pulsed dye laser (PDL) has been developed on the concept of selective photothermolysis and has revolutionized PWS treatment. Eventhough the response is variable, substantial blanching can be obtained after several sessions. Greater selectivity and better response have been achieved by modifying PDL parameters such as longer pulse width, longer wavelength, or higher energy fluencies with cooling skin devices. It is known that thick, deep or raised lesions present poor response to conventional treatments. The aim of this study is to review the different lasers and other light sources which are developing for the treatment of PWS and other vascular lesions

Effects of hypobaric pressure on human skin: implications for cryogen spray cooling (part II).

BACKGROUND AND OBJECTIVES: Clinical results have demonstrated that dark purple port wine stain (PWS) birthmarks respond favorably to laser induced photothermolysis after the first three to five treatments. Nevertheless, complete blanching is rarely achieved and the lesions stabilize at a red-pink color. In a feasibility study (Part I), we showed that local hypobaric pressure on PWS human skin prior to laser irradiation induced significant lesion blanching. The objective of the present study (Part II) is to investigate the effects of hypobaric pressures on the efficiency of cryogen spray cooling (CSC), a technique that assists laser therapy of PWS and other dermatoses. STUDY DESIGN/MATERIALS AND METHODS: Experiments were carried out within a suction cup and vacuum chamber to study the effect of hypobaric pressure on the: (1) interaction of cryogen sprays with human skin; (2) spray atomization; and (3) thermal response of a model skin phantom. A high-speed camera was used to acquire digital images of spray impingement on in vivo human skin and spray cones generated at different hypobaric pressures. Subsequently, liquid cryogen was sprayed onto a skin phantom at atmospheric and 17, 34, 51, and 68 kPa (5, 10, 15, and 20 in Hg) hypobaric pressures. A fast-response temperature sensor measured sub-surface phantom temperature as a function of time. Measurements were used to solve an inverse heat conduction problem to calculate surface temperatures, heat flux, and overall heat extraction at the skin phantom surface. RESULTS: Under hypobaric pressures, cryogen spurts did not produce skin indentation and only minimal frost formation. Sprays also showed shorter jet lengths and better atomization. Lower minimum surface temperatures and higher overall heat extraction from skin phantoms were reached. CONCLUSIONS: The combined effects of hypobaric pressure result in more efficient cryogen evaporation that enhances heat extraction and, therefore, improves the epidermal protection provided by CSC.

Confocal microscopy study of nerves and blood vessels in untreated and treated port wine stains: preliminary observations.

BACKGROUND AND OBJECTIVE: Vascular ectasia in port wine stain birthmarks (PWS) might result from reduced innervation with loss of autonomic stimulation. We investigated this theory and evaluated nerve and blood vessel density, and mean blood vessel size in untreated and treated PWS skin. METHODS: Skin biopsy specimens were obtained from uninvolved skin, untreated PWS, PWS with a good response to laser treatment and PWS with a poor response to laser treatment. Confocal microscopy was performed to determine nerve and blood vessel density, and mean blood vessel size. RESULTS: Nerve density was significantly decreased in all PWS sites compared to uninvolved skin. Mean blood vessel diameter was larger in untreated compared to treated PWS. PWS with a good response to treatment had decreased nerve density but blood vessel density and mean diameter was relatively normal. PWS with a poor response to treatment had decreased nerve density but increased blood vessel density and mean blood vessel diameter compared to normal skin. CONCLUSION: Nerve density was decreased in all evaluated PWS sites and this may be a factor in lesion pathogenesis. PWS blood vessel size correlated with pulsed dye laser response and may prove to be a useful prognostic indicator of therapeutic outcome.