We present a noninvasive method to track the concentration of photodynamic therapy drugs in real time. The method is based on measurements of backscattered and fluorescent light with a steady-state fluorescence spectrometer. The ratio of the fluorescent light to the 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.
© 2000 Optical Society of America
Murat Canpolat and Judith R. Mourant, "Monitoring Photosensitizer Concentration by use of a Fiber-Optic Probe with a Small Source-Detector Separation," Appl. Opt. 39, 6508-6514 (2000)