ABSTRACT
References 399
1. INTRODUCTION
Photodynamic therapy (PDT) is a treatment modality that utilizes three elements, a
photosensitizing drug, light, and oxygen, to induce targeted cell death of neoplastic or abnor-
mal tissue (1). Specifically, sensitization of the target tissue is selective and occurs via the
topically or systemically administered photosensitizing agent. After administration, the
photosensitizer is activated by light and reacts with oxygen and other metabolites to
produce highly reactive oxygen intermediates and free radicals that result in destruction of
targeted tissue (2).