Research Papers

Temperature mapping of laser-induced hyperthermia in an ocular phantom using magnetic resonance thermography

[+] Author Affiliations
Saher M. Maswadi

University of Texas Health Science Center, Department of Ophthalmology, San Antonio, Texas?78229

Stephen J. Dodd, Jia-Hong Gao

University of Texas Health Science Center, Research Imaging Center, San Antonio, Texas?78229

Randolph D. Glickman

University of Texas Health Science Center, Department of Ophthalmology, San Antonio, Texas?78229

J. Biomed. Opt. 9(4), 711-718 (Jul 01, 2004). doi:10.1117/1.1751399
History: Received Jun. 24, 2003; Revised Nov. 26, 2003; Accepted Dec. 2, 2003; Online July 12, 2004
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Laser-induced heating in an ocular phantom is measured with magnetic resonance thermography (MRT) using temperature-dependent phase changes in proton resonance frequency. The ocular phantom contains a layer of melanosomes isolated from bovine retinal pigment epithelium. The phantom is heated by the 806-nm output of a continuous wave diode laser with an irradiance of 2.4 to 21.6 W/cm2 in a beam radius of 0.8 or 2.4 mm, depending on the experiment. MRT is performed with a 2T magnet, and a two-turn, 6-cm-diam, circular radio frequency coil. Two-dimensional temperature gradients are measured within the plane of the melanin layer, as well as normal to it, with a temperature resolution of 1°C or better. The temperature gradients extending within the melanin layer are broader than those orthogonal to the layer, consistent with the higher optical absorption and consequent heating in the melanin. The temperature gradients in the phantom measured by MRT closely approximate the predictions of a classical heat diffusion model. Three-dimensional temperature maps with a spatial resolution of 0.25 mm in all directions are also made. Although the temporal resolution is limited in the prototype system (22.9 s for a single image “slice”), improvements in future implementations are likely. These results indicate that MRT has sufficient spatial and temperature resolution to monitor target tissue temperature during transpupillary thermotherapy in the human eye. © 2004 Society of Photo-Optical Instrumentation Engineers.

© 2004 Society of Photo-Optical Instrumentation Engineers

Citation

Saher M. Maswadi ; Stephen J. Dodd ; Jia-Hong Gao and Randolph D. Glickman
"Temperature mapping of laser-induced hyperthermia in an ocular phantom using magnetic resonance thermography", J. Biomed. Opt. 9(4), 711-718 (Jul 01, 2004). ; http://dx.doi.org/10.1117/1.1751399


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