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Determination of the distribution of drug concentration and tissue optical properties for ALA-mediated anal photodynamic therapy

Authors
  • Ong, Yi Hong1
  • Li, Andrew C.1
  • Busch, Theresa M.1
  • Zhu, Timothy C.1
  • 1 Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 19104
Type
Published Article
Journal
Proceedings of SPIE--the International Society for Optical Engineering
Publication Date
Mar 08, 2021
Volume
11628
Identifiers
DOI: 10.1117/12.2581824
PMID: 34083860
PMCID: PMC8171263
Source
PubMed Central
Keywords
Disciplines
  • Article
License
Unknown

Abstract

PDT efficacy depends on the availability and dynamic interactions of photosensitizer, light, and oxygen. Tissue optical properties influence the delivered light dose and impact PDT outcome. In-vivo measurements of tissue optical properties and photosensitizer concentration enable determination of explicit and implicit dose factors affecting PDT and helps to understand the underlying biophysical mechanism of PDT. In this study, we measure tissue optical properties (absorption μa (λ) and scattering μs’ (λ) coefficients) and PpIX concentration in tissue simulating liquid phantoms with a geometry that resembles anal canal. In-vivo light fluence rate and photosensitizer fluorescence of 405nm excitation light source were acquired using a dual-motor continuous wave transmittance spectroscopy system. We characterized the tissue optical properties correction factor of fluorescence signal using a series of tissue simulating phantoms with known PpIX concentrations and with absorption coefficient between 0.1 – 0.9 cm−1 and reduced scattering coefficient between 5 – 40 cm−1. The results demonstrated that our spectroscopy system could determine the distribution of tissue optical properties and PPIX concentration during anal PDT.

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