In-vivo optical attenuation in normal rat brain and its implication in PDT (Invited Paper)

Investigation is made of the optical attenuation depth in Fisher rat brain at different wavelengths and during PDT treatment. The attenuation depth gradually increased from 0.6 to 1.7 mm when the irradiating light wavelength increased from 450 nm to 710 nm. During PDT treatment (Photofrin II 48 hours prior to 633 nm, 5 mm diameter surface irradiation of 100 J/cm² and 100 mW/cm²), the attenuation depth was found relatively constant (variation <20%).