Abstract

Calculations of the transmission and 2-D spatial distribution of the radiant energy fluence have been carried out with a discrete ordinates program. A Monte Carlo program for microcomputers is under development. Optical properties of tissues were obtained from measurements on specimens. An absorbing zone (e.g., tumor) depressed the fluence, but it recovered at distances beyond 1 cm. Escape from small sections of tissue decreased the fluence significantly if the surface was less than three diffusion lengths (6–12 mm) from the dose point. Measurements of the absolute energy fluence rate were made with a calibrated isotropic fiber-optics probe and photodetector. This probe can be used to monitor the energy fluence rate during irradiation, assuring that the correct dose is delivered despite changes in optical power or in the attenuation of tissues. The probe is recommended for routine use in photodynamic therapy. The distal end should be located at the deepest part of the tumor.

© 1988 Optical Society of America