Nonlinear photodynamic therapy. Photochemical dose levelling within a tumor by saturating a photosensitizer's triplet states.

The photodynamic therapy involving saturation of triplet state of a photosensitizer by short high-energy light pulses was studied theoretically. The possibility of creating a uniform therapeutic dose distribution throughout a large tumor using both surface and interstitial irradiation is shown. Possible thickness of the treated tissue layer and the required duration of the PDT session are estimated.