How photobleaching affects dosimetry and fluorescence monitoring of PDT in turbid media

Steven L. Jacques, Rachel Joseph, Gary Gofstein

Research output: Chapter in Book/Report/Conference proceedingConference contribution

33 Scopus citations

Abstract

The observation of photobleaching is affected by the tissue optics. The apparent time constant for photobleaching at a particular irradiance of light is related to the true photobleaching constant, D, in J/cm2 by a factor which depends on the tissue optical properties, especially at the wavelength used to excite fluorescence. We report in vivo experimental measurements of protoporphyrin IX (PPIX) photobleaching in subcutaneous rat tumors which suggest tentative values for D of about 105 ± 23 J/cm2 during 630 nm irradiation. The effect of such a photobleaching constant on the photodynamic dose, P, in photons/cm3 absorbed by PPIX, was calculated. We estimate that an initial PPIX concentration of about 0.2 μg/ml is required such that P reaches twice the toxic threshold photodynamic dose, Pth, which is assumed to be similar to the 8.6 × 1017 value cited for PhotofrinII. The above estimates are subject to further investigation. This paper presents the mathematics underlying the process of photobleaching and its observation based on fluorescence monitoring.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsThomas J. Dougherty, Abraham Katzir
PublisherPubl by Society of Photo-Optical Instrumentation Engineers
Pages168-179
Number of pages12
ISBN (Print)0819411086
StatePublished - Dec 1 1993
EventOptical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy II - Los Angeles, CA, USA
Duration: Jan 16 1993Jan 17 1993

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume1881
ISSN (Print)0277-786X

Other

OtherOptical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy II
CityLos Angeles, CA, USA
Period1/16/931/17/93

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

Cite this

Jacques, S. L., Joseph, R., & Gofstein, G. (1993). How photobleaching affects dosimetry and fluorescence monitoring of PDT in turbid media. In T. J. Dougherty, & A. Katzir (Eds.), Proceedings of SPIE - The International Society for Optical Engineering (pp. 168-179). (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 1881). Publ by Society of Photo-Optical Instrumentation Engineers.