System for providing simultaneous PDT delivery and dual spectroscopic monitoring in clinical basal cell carcinoma therapy

Abstract

Photodynamic therapy using 5-aminolevulinic acid is an effective therapy for treating basal cell carcinoma, characterized by high lesion clearance and excellent cosmetic outcomes. Treatment optimization and lesion-tailored treatments making use of real-time treatment assessment promise still greater efficacy and improved comfort for patients. In order to monitor treatment parameters during therapy, instrumentation of our own design delivers a 633 nm treatment beam while simultaneously collecting fluorescence spectra. Fluorescence spectra from 650-800 nm are corrected for the effects of tissue optical properties and report protoporphyrin IX (PpIX) photobleaching as well as photoproduct dynamics in the lesion and in the perilesion margin during therapy. Brief treatment interruptions are made for acquisition of white light reflectance spectra from 420-800 nm that are used to generate corrections to fluorescence spectra and can be used to deduce blood volume and hemoglobin oxygen saturation. LabVIEW and Matlab scripts are used for real-time data analysis. Measurements have been made on 5 patients (7 BCC lesions) with a treatment fluence rate of 150 mW cm-2 and on 5 additional patients (5 BCC lesions) at 10 mW cm-2. Measurements are made for each lesion until greater than 90% photobleaching of PpIX is detected at which point the balance of the prescribed fluence is delivered at 150 mW cm-2 without interruption. PpIX bleaching rates between the two fluence rates varied significantly. These measurements were carried out during ALA-PDT treatment of BCC as part of a pilot study designed to guide treatment fluence and fluence rates in an anticipated clinical trial.