A feasibility study of singlet oxygen explicit dosmietry (SOED) of PDT by intercomparison with a singlet oxygen luminescence dosimetry (SOLD) system.

An explicit dosimetry model has been developed to calculate the apparent reacted 1O2 concentration ([1O2]rx) in an in-vivo model. In the model, a macroscopic quantity, g, is introduced to account for oxygen perfusion to the medium during PDT. In this study, the SOED model is extended for PDT treatment in phantom conditions where vasculature is not present; the oxygen perfusion is achieved through the air-phantom interface instead. The solution of the SOED model is obtained by solving the coupled photochemical rate equations incorporating oxygen perfusion through the air-liquid interface. Experiments were performed for two photosensitizers (PS), Rose Bengal (RB) and Photofrin (PH), in solution, using SOED and SOLD measurements to determine both the instantaneous [1O2] as well as cumulative [1O2]rx concentrations, where [1O2] rx = (1/τΔ) · ∫[1O2]dt. The PS concentrations varied between 10 and 100 mM for RB and ~200 mM for Photofrin. The resulting magnitudes of [1O2] were compared between SOED and SOLD.