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Proceedings Paper

Targeted hyperthermia in prostate with an MR-guided endorectal ultrasound phased array: patient specific modeling and preliminary experiments
Author(s): Vasant A. Salgaonkar; Punit Prakash; Juan Plata; Andrew Holbrook; Viola Rieke; John Kurhanewicz; I-C. Hsu; Chris J. Diederich
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Paper Abstract

Feasibility of hyperthermia delivery to the prostate with a commercially available MR-guided endorectal ultrasound (ERUS) phased array ablation system (ExAblate 2100, Insightec, LTD) was assessed through computer simulations and ex vivo experiments. The simulations included a 3D FEM-based biothermal model, and acoustic field calculations for the ExAblate phased array (2.3 MHz, 2.3x4.0 cm2) using the rectangular radiator method. Array beamforming strategies were investigated to deliver 30-min hyperthermia (<41 °C) to focal regions of prostate cancer, identified from MR images in representative patient cases. Constraints on power densities, sonication durations and switching speeds imposed by ExAblate hardware and software were incorporated in the models. T<41 °C was calculated in 14-19 cm3 for sonications with planar or diverging beam patterns at 0.9-1.2 W/cm2, and in 3-10 cm3 for curvilinear (cylindrical) or multifocus beam patterns at 1.5-3.3 W/cm2, potentially useful for treating focal disease in a single posterior quadrant. Preliminary experiments included beamformed sonications in tissue mimicking phantom material under MRI-based temperature monitoring at 3T (GRE TE=7.0 ms, TR=15 ms, BW=10.5 kHz, FOV=15 cm, matrix 128x128, FA=40°). MR-temperature rises of 2-6 °C were induced in a phantom with the ExAblate array, consistent with calculated values and lower power settings (~0.86 W/cm2, 3 min.). Conformable hyperthermia may be delivered by tailoring power deposition along the array length and angular expanse. MRgERUS HIFU systems can be controlled for continuous hyperthermia in prostate to augment radiotherapy and drug delivery. [FUS Foundation, NIH R01 122276, 111981].

Paper Details

Date Published: 26 February 2013
PDF: 8 pages
Proc. SPIE 8584, Energy-based Treatment of Tissue and Assessment VII, 85840U (26 February 2013); doi: 10.1117/12.2004609
Show Author Affiliations
Vasant A. Salgaonkar, Univ. of California, San Francisco (United States)
Punit Prakash, Univ. of California, San Francisco (United States)
Juan Plata, Stanford Univ. (United States)
Andrew Holbrook, Stanford Univ. (United States)
Viola Rieke, Univ. of California, San Francisco (United States)
John Kurhanewicz, Univ. of California, San Francisco (United States)
I-C. Hsu, Univ. of California, San Francisco (United States)
Chris J. Diederich, Univ. of California, San Francisco (United States)

Published in SPIE Proceedings Vol. 8584:
Energy-based Treatment of Tissue and Assessment VII
Thomas P. Ryan, Editor(s)

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