Dependence of photodynamic threshold dose on treatment parameters in normal rat liver in vivo

Thomas J. Farrell; Brian C. Wilson; Michael S. Patterson; Rowena Chow

doi:10.1117/12.44053

1 June 1991 Dependence of photodynamic threshold dose on treatment parameters in normal rat liver in vivo

Thomas J. Farrell, Brian C. Wilson, Michael S. Patterson, Rowena Chow

Proceedings Volume 1426, Optical Methods for Tumor Treatment and Early Diagnosis: Mechanisms and Techniques; (1991) https://doi.org/10.1117/12.44053
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

The validity and utility of the measurement of the photodynamic threshold dose as an in vivo tool for quantitatively assessing the effectiveness of performing photodynamic therapy (PDT) using differing photosensitizers, irradiation protocols and adjuvant treatments was examined. The depth of the boundary between necrotic tissue and normal tissue following surface irradiation of normal rat liver was used to calculate the photodynamic threshold, a quantity independent of photosensitizer concentration, light fluence and wavelength. PDT was performed using Photofrin II to investigate the changes in photodynamic threshold using four different treatment conditions. Using a range of values for photosensitizer concentration and total light fluence, the photodynamic threshold was found to be independent of these parameters and estimated as (3.4 +/- 0.3) X 1018 photons cm-3. Using periodic light irradiation schedules to determine if diffusion of 3O2 affects the threshold measurement, the photodynamic thresholds were found not to be significantly different from those using normal irradiation which suggests that this model is not sensitive to this parameter. PDT was performed in conjunction with hyperthermia and significant reductions in the photodynamic threshold were obtained if hyperthermia followed PDT but not if hyperthermia preceded PDT. Finally, the effects of the radio-protecting agents WR-77913 and WR-2721 were examined and significant increases in the photodynamic threshold were obtained for PDT performed following injection of sufficient quantity of either radio-protecting drug.

Citation Download Citation

Thomas J. Farrell, Brian C. Wilson, Michael S. Patterson, and Rowena Chow "Dependence of photodynamic threshold dose on treatment parameters in normal rat liver in vivo", Proc. SPIE 1426, Optical Methods for Tumor Treatment and Early Diagnosis: Mechanisms and Techniques, (1 June 1991); https://doi.org/10.1117/12.44053

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