Predicting fluence measurements from a cylindrical diffusing tip using the P3-approximation

Dwayne J. Dickey; Kevin Partridge; Ronald B. Moore; John Tulip

doi:10.1117/12.469350

6 June 2002 Predicting fluence measurements from a cylindrical diffusing tip using the P3-approximation

Dwayne J. Dickey, Kevin Partridge, Ronald B. Moore, John Tulip

Proceedings Volume 4612, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XI; (2002) https://doi.org/10.1117/12.469350
Event: International Symposium on Biomedical Optics, 2002, San Jose, CA, United States

Abstract

Photodynamic Therapy (PDT) is becoming a popular treatment modality for many superficial cancers and several non-malignant diseases. The use of PDT to treat solid tumors has been limited because there is currently is no clinically acceptable method of either characterizing the optical parameters of a target tissue or of determining dose delivered to the target tissue volume as delivered by a fibreoptic terminated in a cylindrical diffusing tip. Accurate light dosimetry methods, such as the Monte Carlo method, are of limited clinical utility. In this paper we describe the use of the P3-Approximation to optically characterize a light scattering and absorbing medium. Tissue characterization calculations made using the P3-Approximation are analytical and may be performed much faster than with numerical modeling. The process time needed to estimate the dose distribution is sufficiently short to permit iterative adjustment of the light source distribution to account for tissue inhomogeneities, in real time. P3-Approximation based optical dosimetry should be sufficiently fast to be incorporated into an iterative feedback control algorithm for the distribution of light across an interstitial source array. With the optical coefficients furnished by the P3-Approximation, the light dose delivered to the medium from a cylindrical fibreoptic source can be accurately calculated using a novel formulation of Diffusion Theory. The cylindrical fibreoptic diffuser is modeled as a Huygen's array: a finite yet continuous array of isotropic point sources. The predicted light fluence distribution from the Huygen's array compares favorably with experimental fluence measurements.

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Dwayne J. Dickey, Kevin Partridge, Ronald B. Moore, and John Tulip "Predicting fluence measurements from a cylindrical diffusing tip using the P3-approximation", Proc. SPIE 4612, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XI, (6 June 2002); https://doi.org/10.1117/12.469350

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KEYWORDS

Tissue optics

Scattering

Diffusion

Light scattering

Absorption

Photodynamic therapy

Francium

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