Noninvasive thermography of laser-induced hyperthermia using magnetic resonance

Saher M. Maswadi; Randolph D. Glickman; Stephen J. Dodd; Jia Hong Gao

doi:10.1117/12.527809

1 July 2004 Noninvasive thermography of laser-induced hyperthermia using magnetic resonance

Saher M. Maswadi, Randolph D. Glickman, Stephen J. Dodd, Jia Hong Gao

Proceedings Volume 5319, Laser Interaction with Tissue and Cells XV; (2004) https://doi.org/10.1117/12.527809
Event: Biomedical Optics 2004, 2004, San Jose, CA, United States

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.

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Saher M. Maswadi, Randolph D. Glickman, Stephen J. Dodd, and Jia Hong Gao "Noninvasive thermography of laser-induced hyperthermia using magnetic resonance", Proc. SPIE 5319, Laser Interaction with Tissue and Cells XV, (1 July 2004); https://doi.org/10.1117/12.527809

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KEYWORDS

Temperature metrology

Laser tissue interaction

Thermal modeling

Magnetic resonance imaging

Laser scattering

Laser therapeutics

Diffusion

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