Monitoring blood volume fraction and oxygen saturation in port-wine stains during vascular targeted photodynamic therapy with diffuse reflectance spectroscopy: Results of a preliminary case study

Abstract Objective: Monitoring dynamic changes during vascular targeted photodynamic therapy (V-PDT) for port-wine stains (PWS) is crucial for achieving an optimal therapeutic outcome. The present investigation is a preliminary research study designed to quantify and monitor the vascular parameters, e.g., blood volume fraction (BVF) and oxygen saturation (StO2), of a PWS lesion by using diffuse reflectance spectroscopy (DRS) before and during V-PDT. Material and methods: A portable DRS detection system was developed with an appropriate source-detector distance of 520 μm for fiber-optic probe. The diffuse reflectance spectra from 450 to 800 nm in specific regions of interest (ROIs) within a PWS lesion were recorded before and 3, 5, 10, 15, and 20 min during V-PDT. In order to extract the optical properties and vascular parameters of the PWS lesion, a modified well-known diffusion theory model with a correction factor for the vessel package effect was employed to analyze the steady state-diffuse reflectance spectra. Results: The corrected reflectance spectra of the PWS lesion can be fitted very well with the modified diffusion theory model. Differences in pretreatment values of BVF and StO2 as well as changes in these parameters were observed between two ROIs during V-PDT. Conclusion: The ability of using DRS for quantifying and monitoring the BVF and StO2 of a PWS lesion has been assessed. The preliminary data suggest that the clinical V-PDT efficiency is affected by the heterogeneity of the PWS lesion. DRS may have the potential to characterize the PWS lesion and to monitor V-PDT response.