Determination of optical and microvascular parameters of port wine stains using diffuse reflectance spectroscopy

Characterizing port wine stains (PWS) with its optical parameters [i.e. absorption coefficient (μ_a) and reduced scattering coefficient (μ_s‘)] and microvascular parameters [i.e. blood volume fraction (BVF), mean vessel diameter (MVD), and oxygen saturation (StO₂)] is extremely important for elucidating the mechanisms for its light-based treatments, such as pulsed dye laser and photodynamic therapy. In this study, a customized diffuse reflectance spectroscopy (DRS) probe with an appropriate source-detector distance was used to measure the diffuse reflectance spectra of PWS lesions in clinical practice. The results demonstrate that optical parameters of different types of PWS lesions can be accurately extracted by fitting the DRS with diffusion equation. Since the sampling depth of the probe coincides with the depth distribution of abnormal vasculature in PWS, the obtained microvascular parameters of PWS lesions that changed from pink to purple are in agreement with the corresponding physiological conditions. This study suggests that DRS can be utilized to quantitatively determine the optical and microvascular parameters of PWS lesions, which have the potential for planning the protocol and predicting the efficiency for light-based PWS treatments.