Time- and wavelength resolved spectroscopy of photosensitizers in vivo using femtosecond white light

A technique allowing simultaneous determination of the optical properties in vivo over a large wavelength region, using diffusively, femtosecond white light pulses, was applied in the study of rats. Several rats with a colon adenocarcinoma inoculated in the muscle of the hind leg were intravenously injected with a di-sulphonated aluminium phthalocyanine (AlS₂Pc). Measurements were performed on the tumour area, as well as on normal muscle tissue. The absorption was evaluated between 600 and 850 nm. Animals not given any photosensitizer served as controls, to obtain the tissue endogenous absorption spectrum, which was subtracted from the spectrum obtained in the injected animals. Preliminary experiments were also performed using other photosensitizers. Results from the study were used to validate the technique.