Conference on Biomedical Diagnostic, Guidance, and Surgical-Assist Systems II, San-Jose, Costa Rica, 25 - 26 January 2000, vol.3911, pp.10-18
We present a novel minimally invasive method to measure the concentration of photodynamic therapy drugs in real time. The method is based on measurements of backscattered and fluorescence Light using a steady state fluorescence spectrometer. The ratio of the fluorescence to scattered light is found to be linearly proportional to the absorption coefficient of the photosensitizer. The fiber-optic probe used for the measurements has a small source-detector separation, therefore the measurements could be performed through the working channel of an endoscope.