6. Photochemical or photodynamic effect

Photodynamic therapy, commonly referred to by the acronym PDT for "PhotoDynamic Therapy", aims to destroy pathological tissue by means of a photochemical reaction. The principle involves marking pathological tissue with an exogenous chemical agent (photosensitizer), then illuminating it with light of the appropriate wavelength to induce a cascade of photochemical reactions leading to the destruction of the treated lesion. The method is based on a two-step process: (i) first, a photosensitizer or a substance that induces the production of this photosensitizer is applied or injected into the area to be treated, resulting in an accumulation of photosensitizer; (ii) then, the area is illuminated with light of a wavelength that is absorbed by the photosensitizer. The therapeutic effect is obtained through low-irradiance illumination (a few tens of mW/cm ² ...