SonoKnife: Feasibility of a line-focused ultrasound device for thermal ablation therapy

• Published in: Medical physics (Lancaster) 2011-07, Vol.38 (7), p.4372-4385
• Main Authors: Chen, Duo, Xia, Rongmin, Chen, Xin, Shafirstein, Gal, Corry, Peter M., Griffin, Robert J., Penagaricano, Jose A., Tulunay-Ugur, Ozlem E., Moros, Eduardo G.
• Format: Article
• Language: English
• Subjects: acoustic edge; Acoustic modeling; Acoustic radiation pressure; Acoustic transducers; Acoustical medical instrumentation and measurement techniques; Biomedical instrumentation and transducers, including micro‐electro‐mechanical systems (MEMS); biomedical transducers; biomedical ultrasonics; biothermics; Biothermics and thermal processes in biology; Cancer; Computer Simulation; Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Feasibility Studies; focused ultrasound; Gels; High-Intensity Focused Ultrasound Ablation - instrumentation; Humans; line-focus; liver; Medical use of ultrasonics for tissue modification (permanent and temporary); Models, Biological; patient treatment; phantoms; SonoKnife; Sound pressure; Therapeutic applications; thermal ablation; Thermotherapy Physics; Transducers; tumours; ultrasonic transducers; Ultrasonography
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.3601017

Purpose: To evaluate the feasibility of line-focused ultrasound for thermal ablation of superficially located tumors. Methods: A SonoKnife is a cylindrical-section ultrasound transducer designed to radiate from its concave surface. This geometry generates a line-focus or acoustic edge. The motivation for this approach was the noninvasive thermal ablation of advanced head and neck tumors and positive neck nodes in reasonable treatment times. Line-focusing may offer advantages over the common point-focusing of spherically curved radiators such as faster coverage of a target volume by scanning of the acoustic edge. In this paper, The authors report studies using numerical models and phantom andex vivo experiments using a SonoKnife prototype. Results : Acoustic edges were generated by cylindrical-section single-element ultrasound transducers numerically, and by the prototype experimentally. Numerically, simulations were performed to characterize the acoustic edge for basic design parameters: transducer dimensions, line-focus depth, frequency, and coupling thickness. The dimensions of the acoustic edge as a function of these parameters were determined. In addition, a step-scanning simulation produced a large thermal lesion in a reasonable treatment time. Experimentally, pressure distributions measured in degassed water agreed well with acoustic simulations, and sonication experiments in gel phantoms andex vivo porcine liver samples produced lesions similar to those predicted with acoustic and thermal models. Conclusions : Results support the feasibility of noninvasive thermal ablation with a SonoKnife.