Fluorescence Diagnosis of Damage to Tumor Tissues During Photodynamic Therapy with the Photosensitizer Photolon.

We have studied the feasibility of using an indotricarbocyanine dye as a marker for the efficacy of photodynamic therapy (PDT) of cancers with the photosensitizer Photolon. We have established that on exposure to laser emission at λ = 667 nm with an exposure dose of 100 J/cm, we observe that the Photolon concentration drops by about a factor of two in the exposed part of the tumor, while the concentration of the indotricarbocyanine dye does not change in any region of the tumor node. We have observed a correlation between the change in the shape of the fluorescence spectra of the indotricarbocyanine dye in vivo in the 780-880 nm resulting from a PDT session with the photosensitizer Photolon and the extent of damage to the tumor tissues. Changes in the shape of the fluorescence spectrum of the dye are interpreted in terms of a model involving the appearance of absorption by different forms of hemoglobin, and changes in their ratio in the exposed part of the tumor due to consumption of molecular oxygen. [ABSTRACT FROM AUTHOR]