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Proceedings Paper

Calculation of isofluence contours for PDT application
Author(s): Stefan B. Spaniol; Dagmar Kobe; Volkhard Abraham; Peter Nothof; Stephan Schmidt; Dieter Krebs; Wolfgang Ertmer
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Paper Abstract

The aim of this study was to calculate the light fluence for various PDT applications with a Monte Carlo method. Different applicator geometries and the related illuminations are computed in a 3D-multilayer tissue model. The applicators we calculated include various surface geometries, intensity and angular profiles as well as tissue parameter variations, and different wavelengths. The resulting fluence contours in conjunction with a certain dye concentration allow a prediction of the expected damage zone after PDT in the tumor tissue. To measure tissue parameters ex vivo we built up a spectrometer consisting of two integrating spheres. The light source we use is a cw Ti:sapphire laser tunable from about 670 nm to 760 nm without change of optics. We use a combination of direct and indirect measurements. By estimating the specular reflection and direct transmission from a tissue sample (approximately 490 micrometers ) we get the refractive index n and the extinction coefficient (mu) (tau ). We also measure the diffuse reflection as well as the diffuse transmission with the integrating spheres. To calculate the missing parameters (mu) a and g we use an inverse Monte Carlo simulation (MCS) with the Henyey-Greenstein phase function. Simulation of the tissue sample including the boundary and geometry effects leads to absorption coefficients that are up to a factor of 3 lower in comparison to good analytical models. The loss of diffuse light can be taken into consideration.

Paper Details

Date Published: 17 August 1994
PDF: 7 pages
Proc. SPIE 2134, Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards, (17 August 1994); doi: 10.1117/12.182941
Show Author Affiliations
Stefan B. Spaniol, Univ. Bonn (Germany)
Dagmar Kobe, Univ. Bonn (Germany)
Volkhard Abraham, Univ. Bonn (Germany)
Peter Nothof, Univ. Bonn (Germany)
Stephan Schmidt, Univ. Bonn (Germany)
Dieter Krebs, Univ. Bonn (Germany)
Wolfgang Ertmer, Univ. Bonn (Germany)

Published in SPIE Proceedings Vol. 2134:
Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards
Steven L. Jacques; David H. Sliney; Michael Belkin, Editor(s)

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