Effects of fluence rate on cytoxicity during photodynamic therapy

Theresa M. Sitnik; Barbara W. Henderson

doi:10.1117/12.273493

8 May 1997 Effects of fluence rate on cytoxicity during photodynamic therapy

Theresa M. Sitnik, Barbara W. Henderson

Proceedings Volume 2972, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy VI; (1997) https://doi.org/10.1117/12.273493
Event: BiOS '97, Part of Photonics West, 1997, San Jose, CA, United States

Abstract

Production of ¹O₂ during PDT may be limited as a consequence of tissue oxygen depletion by the photodynamic process. This may in turn limit cytotoxicity during PDT. One possible way of controlling oxygen consumption during treatment is through modification of fluence rate. We have studied the impact of fluence rate on tumor oxygenation and direct PDT cytotoxicity using the RIF murine tumor and the photosensitizer Photofrin. Both fluence rates caused an acute decrease in tumor pO₂ to severely hypoxic levels. With 150 mW/cm² light median pO₂ remained low during prolonged exposure, while with 30 mW/cm² light median pO₂ values recovered to above control levels. When tumors treated with 135 J/cm² at each fluence rate were tested for cell survival in a clonogenic assay, 30 mW/cm² significantly decreased both cell clonogenicity and plating efficiency compared to light-only controls. Slight but insignificant decreases were found with 150 mW/cm². During in vitro PDT the fluence rate of light delivery had no effect on cell survival. In summary, we have found that low fluence rate improves tumor oxygenation and direct cell effects during PDT.

Citation Download Citation

Theresa M. Sitnik and Barbara W. Henderson "Effects of fluence rate on cytoxicity during photodynamic therapy", Proc. SPIE 2972, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy VI, (8 May 1997); https://doi.org/10.1117/12.273493

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