Invited Symposium: Photodynamic Therapy
Farrell, TJ. (Dept. Medical Physics, Hamilton Regional Cancer Centre and McMaster University, Canada)
In photodynamic therapy (PDT) light absorption by a photosensitizer initiates chemical reactions which result in cell death. The eventual biological effect of treatment depends on the fluence of activating light, the intial concentration of photosensitizer and, for many PDT agents, the concentration of oxygen. Non or minimally invasive measurement of any of these is a challenge in the clinical environment. In addition, these quantities may change dynamically during a PDT treatment due to, for example, photochemical oxygen depletion or vascular shutdown. PDT dosimetry would be greatly simplified if there were a real-time measure of the yield of cytotoxic products which could be performed non-invasively on individual patients. In recent years a number of investigators have proposed that photobleaching of the sensitizer, or some other endogenous fluorophore, might serve this function. In this paper we will examine the conditions necessary for this to be true and what quantities would provide the most useful information. We will also examine the limitations of fluorescence-based photobleaching measurements and strategies to improve their utility.
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|Patterson, M; Farrell, TJ.; (1998). Photobleaching as a Potential Monitor of Photodynamic Therapy. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/rainbow/patterson0765/index.html|
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