Oxygen Monitoring During Pnotodynamic Therapy Of Port Wine Stains

Monitoring dynamic changes during vascular targeted photodynamic therapy (V-PDT) for port-wine stains (PWS) is crucial for achieving an optimal therapeutic outcome. In particular, oxygen saturation (StO2) is a direct oxygen dosimetric parameter for V-PDT as well as considered as a parameter for assessment of the closure of the blood vessels. This thesis presents a customized diffuse reflectance spectroscopy measurement system for PWS characterization and the preliminary results of its application in quantifying and monitoring the vascular parameters, e.g. blood volume fraction (BVF) and oxygen saturation (StO2), of a PWS lesion during V-PDT of PWS.The customized portable DRS detection system was developed with an optimized fiber-optic probe The diffuse reflectance spectra were fitted by a modified dipole diffuse reflectance relation which holds its validation even in the high absorption conditions. This system was calibrated by phantom made by Intralipid while its accuracy was tested by Monte Carlo simulation. In order to further validate the feasibility of this system to extract optical properties and micro vascular parameters of different kinds of PWS, patients with different types of PWS were classified into four groups and their corresponding DRS were measured and analysis. Furthermore, this system was utilized to monitoring the blood volume fraction (BVF) and StO2, of a PWS lesion during V-PDT of PWS. Two regions of interest (ROIs) of the PWS skin were assessed before V-PDT, and their BVF and StO2 was monitored at 3,5,10,15 and 20 min during V-PDT during V-PDT. The treatment responses of these two ROIs were followed up 3 months after treatment.Our results showed that the probe with source-detector (S-D) distance of 520 can increase the sensitivity of the obtained DRS to the reduced scattering coefficient (μs’) as well as to meet the requirement of sampling the vasculature in PWS skin. Thus, the system was sensitive to the optical properties. The corrected reflectance spectra of a PWS lesion can be fitted very well with the modified diffusion theory model. The obtained microvascular parameters changes from Ⅰ-Ⅳ types of PWS are in agreement with physiological changes which suggest our setup is reliable and sensitive to the lesional varied. Differences in pretreatment values of BVF and StO2 as well as changes in these parameters were observed between two ROIs during V-PDT. 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. This study indicates that DRS can be utilized to determine the optical and microvascular parameters of PWS lesions, which hold the potential for planning the protocol and predicting the efficiency for light-based PWS treatments.