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Proceedings Paper

Modeling PpIX-effective fluence rate in tissue for multiple light sources used in photodynamic therapy of skin (Conference Presentation)

Paper Abstract

In recent years, numerous publications have documented the growing consensus among dermatologists for daylight-photodynamic therapy (dPDT) treatment of Actinic Kerasotis (AK), with additional evidence supporting treatment of certain non-melanoma skin cancers (NMSC). While these publications aim to address the minimum effective surface-irradiance required for successful clearance, our current work investigates how the tissue optical properties influence the fluence rate within tissue. While it is known red and blue light will have drastically different attenuation profiles in tissue, it is harder to quantify this for broad-spectrum light sources. Our model aims to expand the current PpIX-weighted irradiance metric by incorporating a clinically relevant depth distribution factor. Using a 7-layer skin model, Monte Carlo simulations of optical photons ranging from 350nm – 900nm provide insight into the potential depth of activation of the photosensitizer. Additionally, these models can be applied to known light spectra for both narrow-band conventional treatments (415nm, 633nm), as well as for the Sun and other white light sources (CFL, Halogen). Using this model, we show even when the effective surface-irradiance of the Sun is 4x a halogen light source, the effective fluence within the top 3mm of tissue is generally equivalent, due to the higher proportion of UV-blue light in Sun spectrum which is highly attenuated within the first 50m. We plan to use this model to inform which light source or light combinations would be most appropriate for specific lesion morphologies.

Paper Details

Date Published: 4 March 2019
Proc. SPIE 10860, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXVIII, 108600Q (4 March 2019); doi: 10.1117/12.2510162
Show Author Affiliations
Ethan Philip M. LaRochelle, Dartmouth College (United States)
Kayla Marra, Dartmouth College (United States)
Robert E. LeBlanc, Geisel School of Medicine, Dartmouth College (United States)
Michael S. Chapman, Geisel School of Medicine, Dartmouth College (United States)
Edward V. Maytin, Cleveland Clinic (United States)
Tayyaba Hasan, Wellman Ctr. for Photomedicine (United States)
Massachusetts General Hospital (United States)
Harvard Medical School (United States)
Brian W. Pogue, Dartmouth College (United States)

Published in SPIE Proceedings Vol. 10860:
Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXVIII
David H. Kessel; Tayyaba Hasan, Editor(s)

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