Analysis of Kinetics and Efficacy of Anti-Cancer via Oxygen-Enhanced Photodynamic Therapy

Abstract

Photodynamic therapy (PDT has been widely used in many medical applications. PDT for anti-cancer is one of the clinically important subjects. This study will analyze the photochemical kinetics and the efficacy of anti-cancer via the critical factors including: the concentrations of photosensitizers and oxygen in the treated target, the exposure time, intensity and does (energy) of the light applied to the target. To achieve high efficacy, one requires the oxygen source term to re-supply the depletion of oxygen and photosensitizers. Higher light intensity has faster rising curve of the efficacy, but it reaches the same steady-state value as that of low intensity. The efficacy follows the Bunsen-Roscoe law (BRL) of reciprocity only when there is no oxygen source term. Higher initial concentration of oxygen and photosensitizers, C0, always provide higher efficacy. To achieve the same efficacy, minimum dose and/or less exposure time for accelerated procedure may be achieved by using a higher intensity (but same dose) for the case of P=0. However, with P>0, higher intensity requires a higher fluence to achieve the same efficacy and it does not follow the BRL reciprocity law.