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Proceedings Paper

Noninvasive thermography of laser-induced hyperthermia using magnetic resonance
Author(s): Saher M. Maswadi; Randolph D. Glickman; Stephen J. Dodd; Jia Hong Gao
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Paper Abstract

The possibility to induce selective hyperthermia in a target tissue or organ is of great interest for the treatment of cancer and other diseases. An emerging application of thermotherapy is for choroidal neovascularization, a complication of age-related macular degeneration. The therapy is currently limited because the temperature required for optimal tissue response is unknown. We report here an investigation of near infrared laser-induced heating in an ocular phantom. Magnetic resonance thermography (MRT) was used as a non-invasive method to determine the temperature distribution inside the phantom during exposure to a continuous wave diode laser at 806 nm wavelength with 1 watt maximum output. The laser beam had a quasi-gaussian profile, with a radius of 0.8-2.4 mm at target. High quality temperature images were obtained from temperature-dependent phase shifts in the proton resonance frequency with a resolution of 1deg C or better, using a 2T magnet. A phantom with a layer of bovine RPE melanin of 1.5 mm thickness was used to determine the spatial resolution of the MRT measurements. Three dimensional temperature maps were also constructed showing a spatial resolution of 0.25 mm in all direction. The heat distribution depended on the laser parameters, as well as the orientation of the melanin layer with respect to the incident laser beam. The temperature profiles determined by MRT closely followed predictions of a heat diffusion model, based on the optical properties of infrared light in melanin. These results support the use of MRT to optimize laser-induced hyperthermia in a small organ such as the eye.

Paper Details

Date Published: 1 July 2004
PDF: 12 pages
Proc. SPIE 5319, Laser Interaction with Tissue and Cells XV, (1 July 2004); doi: 10.1117/12.527809
Show Author Affiliations
Saher M. Maswadi, Univ. of Texas Health Science Ctr./San Antonio (United States)
Randolph D. Glickman, Univ. of Texas Health Science Ctr./San Antonio (United States)
Stephen J. Dodd, Univ. of Texas Health Science Ctr./San Antonio (United States)
Jia Hong Gao, Univ. of Texas Health Science Ctr./San Antonio (United States)

Published in SPIE Proceedings Vol. 5319:
Laser Interaction with Tissue and Cells XV
Steven L. Jacques; William P. Roach, Editor(s)

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