Optics of light dosimetry for PDT in superficial lesions versus bulky tumors

Steven L. Jacques

Research output: Contribution to journalConference article

9 Scopus citations

Abstract

The light dosimetry for photodynamic therapy (PDT) for superficial lesions is concerned with ensuring sufficient light in the superficial tissue layer to achieve efficacious PDT. The light dosimetry for bulky tumors is concerned with the maximum depth of effective treatment while expecting over exposure of the tumor surface. The light delivered to a tissue surface does not equal the light received by the superficial region of that tissue. Backscattered light from the underlying tissues augments the surface irradiance to yield a higher fluence rate (W/cm2) in the target superficial tissue layer. The effective irradiance of treatment light, E [W/cm2], seen by a superficial lesion is approximated: E = Eo(1 + 2R(1 + ri)/(1 - ri)) = Eo(1 + 6R) where Eo is the irradiance delivered to the surface, R is the fraction of incident light that escapes the tissue as observable reflectance (typically about 0.30-0.60), and ri is the total internal reflection of light attempting to escape at the air/tissue surface (about 0.50). Hence the factor (1 + 6R) varies from 2.8-4.6. The backscattered light significantly affects the treatment light dose for superficial lesions. The light within a bulky tumor is approximated: E = Eo k exp(-z/delta), where z is the depth in the tissue, k is a backscatter term, k = 3 + 5.1R - 2exp(- 9.7R) (eg., k = 4.1-5.9 for R = 0.30-0.60), and delta is the 1/e optical penetration depth (typically about 0.3-0.5 cm).

Original languageEnglish (US)
Pages (from-to)59-68
Number of pages10
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume4612
DOIs
StatePublished - Jan 1 2002
EventOptical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XI - San Jose, CA, United States
Duration: Jan 19 2002Jan 20 2002

Keywords

  • Biomedical optics
  • Optical dosimetry
  • PDT
  • Photodynamic therapy

ASJC Scopus subject areas

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

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