Positron emission tomography imaging of tumor response after photodynamic therapy.

Positron emission tomography (PET) imaging is a powerful noninvasive tool allowing physiological and biochemical processes to be investigated in vivo at the molecular level. In the clinics, it is currently being used to detect and stage cancer and to assess tumor response following therapy. In cancer research, at the preclinical level, PET in conjunction with a dedicated high-resolution small animal scanner can play an important role in drug development as well as in the evaluation of novel treatment protocols. In this paper, we review the use of PET in assessing tumor response to photodynamic therapy (PDT) and discuss its potential role in the development of novel photosensitizers. This molecular imaging modality is particularly promising for the real-time evaluation of tumor response to therapy both in terms of treatment efficacy and action mechanism.