Threshold Photodynamic (PDT) Effects For Experimental Colonic Photodynamic Therapy.

H. Barr; A. J. MacRobert; P. B. Boulos; C. J. Tralau; S. G. Bown

doi:10.1117/12.952129

15 June 1989 Threshold Photodynamic (PDT) Effects For Experimental Colonic Photodynamic Therapy.

H. Barr, A. J. MacRobert, P. B. Boulos, C. J. Tralau, S. G. Bown

Proceedings Volume 1067, Optical Fibers in Medicine IV; (1989) https://doi.org/10.1117/12.952129
Event: OE/LASE '89, 1989, Los Angeles, CA, United States

Abstract

The existence of a threshold photodynamic dose has been postulated because of the sharp demarcation between an area of PDT necrosis and normal undamaged tissue 1. An experiment was designed to measure the light intensity at various distances from the source of irradiation during PDT. Experiments were performed on normal rodent colon using a standard intravenously injected dose of the photosensitiser aluminium sulphonated phthalocyanine (A1SPc). Irradiation was performed 1 hour after injection of 5mgkg^-1 using an argon pumped dye laser delivering 100mW from the end of the fibre. The time of irradiation was varied and the amount of necrosis measured 72 hours after treatment. The light intensity at specific points could be correlated with the amount of necrosis. Threshold photodynamic effects are important, if a total photodynamic dose (light fluence x photosensitiser concentration) is considered, since selective tumour destruction may be possible if the dosimetry is carefully adjusted to allow a photodynamic thresholdto be reached in the tumour and not in the normal colon. Adjustment of the light or photosensitiser dose can be used to manipulate the effect. Under apprpriate circumstances A1SPc can be photodegraded so that a total threshold photodynamic dose may never be reached in normal colon.

Citation Download Citation

H. Barr, A. J. MacRobert, P. B. Boulos, C. J. Tralau, and S. G. Bown "Threshold Photodynamic (PDT) Effects For Experimental Colonic Photodynamic Therapy.", Proc. SPIE 1067, Optical Fibers in Medicine IV, (15 June 1989); https://doi.org/10.1117/12.952129

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