Fluence rate variability among light delivery devices for esophageal photodynamic therapy

Jarod C. Finlay; Gregory G. Ginsberg; Stephen M. Hahn

doi:10.1117/12.699541

28 February 2007 Fluence rate variability among light delivery devices for esophageal photodynamic therapy

Jarod C. Finlay, Gregory G. Ginsberg, Stephen M. Hahn

Proceedings Volume 6427, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XVI; 642712 (2007) https://doi.org/10.1117/12.699541
Event: SPIE BiOS, 2007, San Jose, California, United States

Abstract

Esophageal photodynamic therapy (PDT) is performed using a photosensitizing agent activated by light delivered via a cylindrically symmetric delivery device containing a diffusing optical fiber. In PDT treatment of dysplastic Barrett's esophagus, considerable variability in results is observed due to the non-uniform delivery of treatment light caused by source geometry and by luminal collapse. We compare the fluence rate at the tissue surface resulting from illumination with bare fiber, a centering balloon catheter (X-Cell, Cooke, Inc), and a fixed diameter transparent dilating catheter (Optical Dilator, Inscope, Ethicon ES). Measurements were made in a solid esophagus-simulating phantom illuminated by 2.5 and 5 cm diffusing fibers with and without each delivery device. The diffuser was coupled to a 630 nm dye laser pumped by a 532 nm KTP laser (LaserScope, Inc.) The total power emitted by the diffuser was 1W. The fluence rate as a function of position along the cavity was measured by a calibrated photodiode connected to an optical fiber with a 0.5 mm isotropic scattering tip, which was moved by a computer-controlled positioner. The mean fluence rate measured when the phantom was illuminated using either the centering balloon or the rigid dilator was approximately 50% less than that measured with a bare fiber. The decrease in fluence rate is due to attenuation of the primary light beam and to reduction in scattering from laterally adjacent points in the phantom. The importance of each of these effects as a function of tissue optical properties was confirmed using Monte Carlo simulation.

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Jarod C. Finlay, Gregory G. Ginsberg, and Stephen M. Hahn "Fluence rate variability among light delivery devices for esophageal photodynamic therapy", Proc. SPIE 6427, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XVI, 642712 (28 February 2007); https://doi.org/10.1117/12.699541

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KEYWORDS

Photodynamic therapy

Diffusers

Esophagus

Monte Carlo methods

Tissue optics

Light scattering

Natural surfaces

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