Fluorescence diagnosis of damage to tumor tissues during photodynamic therapy with the photosensitizer photolon

Abstract

We have studied the feasibility of using an indotricarbocyanine dye as a marker for the effi cacy 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/cm2, 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 fl uorescence 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.