A model-based comparison of implicit and direct dosimetry for ALA-PDT of skin

Photosensitizer fluorescence photobleaching and Singlet Oxygen (O-1(2)) Luminescence Dosimetry (SOLD) are being studied as potential dosimetric tools for ALA-PDT of skin diseases. However, the correlation of both SOLD data and PpIX fluorescence to O-1(2) distribution is difficult to interpret because of the temporal and spatial variations of the PDT parameters (light fluence rate, photosensitizer concentration and oxygen concentration). This work used our dynamic model to investigate both dosimetry approaches for varied PpIX concentration and distribution, and three commonly used treatment wavelengths. The results show that SOLD is much less dependent upon the treatment parameters, which implies it has better potential as a "gold standard" dosimetric tool for clinical PDT.