The concentration of Photofrmn II is needed to determine the dose in photodynamic therapy, and in fluorescence diagnosis of
tumors. A method based on fluorescence was devised which shows promise. Diffusion theory was applied in slab geometry
with closely spaced excitation and emission wavelengths. A function of the measured radiant energy fluences for excitation
and emission, and the depth x, was found that canceled the dependence on depth. A function of the diffusion coefficient and
attenuation coefficient was derived from the measured diffuse reflectance. This function compensated for differences in
absorption and scattering in different tissues, or a calibration phantom and tissue. Comparisons should be made with the
concentration derived in other ways, but the fluorescence method shows promise.
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