基 于 反 射 光 谱 测 量 和 辐 射 反 方 法 的 鲜 红 斑 痣激 光 热 疗 临 床 疗 效 量 化 评 估

Objective Port-wine stains (PWS) are congenital vascular malformations caused by the abnormal dilation of capillaries and venules in the skin. Affecting 0.3%‒0.5% of newborns, PWS typically manifest as pinkish patches on the face and neck that darken and thicken over time, significantly impacting patients’physical and mental well-being. Pulsed dye laser (PDL) therapy, based on selective photothermolysis, is the gold standard for PWS treatment. By targeting hemoglobin in abnormal blood vessels with specific wavelengths, PDL induces thermal damage to the vasculature while sparing surrounding tissues. However, due to variability in skin types, lesion depths, and laser parameters, clinical outcomes often depend on subjective evaluations and physician experience. These limitations underscore the urgent need for objective, quantitative, and noninvasive methods to assess skin structure and monitor treatment efficacy. This study integrates reflectance spectroscopy with an inverse Monte Carlo radiation method to quantify changes in key skin parameters before and after laser treatment. By measuring and reconstructing parameters such as epidermal thickness, melanin volume fraction, blood volume fraction, and blood oxygen saturation, this study establishes a robust framework for evaluating treatment outcomes and optimizing laser parameters. Additionally, it investigates differences in treatment responses between pediatric and adult patients, providing critical insights for personalized therapeutic strategies. Methods Eleven patients with PWS underwent pulsed dye laser (PDL) therapy at a wavelength of 595 nm, with an energy density of 8 J/cm² and a fixed spot diameter of 7 mm. Reflectance spectra of the skin were measured before and after treatment using an HR400 CG-UV-NIR spectrometer (Fig. 1). To enhance efficacy, a double-irradiation strategy was employed, in which the second laser exposure followed the first after five minutes. For spectral analysis, an inverse Monte Carlo radiation method was developed to reconstruct key skin structural parameters. The multilayered skin model (Fig. 2) incorporated the epidermis, papillary dermis, reticular dermis, and subcutaneous tissue. The inverse Monte Carlo radiation method iteratively optimized nine variables—epidermal thickness (d_epi), dermal thickness (d_de), melanin volume fraction (m), epidermal blood volume fraction (b_epi), dermal blood volume fractions (b_pap and b_ret), dermal oxygen saturations (S_pap and S_ret), and the subcutaneous scattering coefficient (μ_s,sub)—to minimize the discrepancy between measured and simulated reflectance spectra (Fig. 3). The simulated spectra showed high concordance with clinical measurements [error <7%, Fig. 4(b)], validating the accuracy of the algorithm. Results and Discussions This study demonstrates that integrating reflectance spectroscopy with the inverse Monte Carlo method provides a robust framework for quantifying skin structural changes and evaluating the efficacy of laser treatment in patients with PWS. Analysis of the reconstructed parameters reveals significant reductions in blood volume fraction and blood oxygen saturation among patients exhibiting vascular blanching, which correlates with superior clinical outcomes. Specifically, the average reduction in blood volume fraction in this group is 11.6%, while blood oxygen saturation decreases by 15.6%, indicating successful obliteration of abnormal vasculature. In contrast, patients with vascular constriction experience more modest changes, with a 7.1% reduction in blood volume fraction and a 4.3% decrease in oxygen saturation, suggesting partial vessel narrowing without complete closure. Cases with no significant effects exhibit minimal changes in reflectance spectra and structural parameters. Pediatric patients demonstrate enhanced therapeutic outcomes compared with adults, attributed to a thinner epidermis and lower melanin content, allowing deeper laser penetration and higher treatment efficiency. For instance, in clinical case Ⅰ (a child), blood volume fraction decreases by 18.9% at three months post-treatment, compared to 7.9% in clinical case Ⅱ (an adult male). These findings underscore the advantages of early intervention and the potential for improved outcomes in children with favorable skin characteristics. Moreover, melanin volume fractions remain stable throughout treatment, with variations below 3%, validating the protective role of cryogen spray cooling in preventing thermal damage to the epidermis. According to reflectance spectra analysis, we categorize treatment responses into three groups: vascular blanching, vascular constriction, and no significant effects. This classification provides insights into the physiological mechanisms underlying therapeutic outcomes, highlighting vascular blanching as the most effective clinical endpoint. These results emphasize the importance of tailoring laser parameters to individual skin characteristics, such as lesion depth, epidermal thickness, and melanin content, to achieve optimal outcomes. This approach demonstrates the potential of quantitative, non-invasive methods to enhance the precision and personalization of laser therapies for PWS and other vascular skin conditions. The proposed method bridges the gap between advanced computational techniques and practical clinical applications by providing objective metrics and real-time monitoring. Conclusions This study demonstrates the efficacy of combining reflectance spectroscopy with an inverse Monte Carlo algorithm for the quantitative, noninvasive assessment of PWS laser treatment. By providing objective metrics for evaluating treatment responses, such as vascular blanching and constriction, this method enhances clinical precision and informs optimal laser parameter selection. It also facilitates real-time monitoring and personalized therapy planning, particularly for pediatric patients, who exhibit superior therapeutic outcomes due to their favorable skin characteristics. Future studies should expand the sample size to validate the generalizability of this method and explore its applicability to other vascular skin lesions, including hemangiomas and spider veins. These findings highlight the potential of integrating advanced optical measurement techniques with computational algorithms to transform dermatological laser therapy.