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

Abstract

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 and ex 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 and ex 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.

Simulation techniques in hyperthermia treatment planning

“…the use of computer clusters and graphical processing units (GPU), may gradually make full-wave 3D US-HTP more applicable (69). However, to date, US-HTP has been used most frequently to optimize or adapt the aperture of US phased-arrays to the tumor location and/or shape (70-72). Nonetheless, the need for US-HTP is becoming more and more apparent in applications where the small focal volume of the US field produced is inadequate for the larger target volumes.…”

Focused ultrasound for treatment of bone tumours

“…Over the past decades, there have been numerous external ultrasound array systems for focused heating in the body, [22][23][24][25][26][27] including one system specifically optimized for small animal treatments [28]. At present, there are three commercial non-invasive ultrasound heating systems that have been integrated within either US or MR imaging systems for image-guidance of FUS treatments in humans: the ExAblate system (InSightec Ltd., Tirat Carmel, Israel) based on the General Electric MR platform [29,30]; the Sonalleve FUS system (Koninklijke Philips Electronics NV, Eindhoven, The Netherlands) based on the Phillips MR platform [31,32]; and the Haifu system (Model JC, Chongqing Haifu Medical Technology Co. Ltd., Chongqing, China) coupled with a B-type ultrasonography system [33].…”

Heating technology for malignant tumors: a review

“…To improve the robustness of treatment planning predictions for ablation, application of probabilistic modeling techniques is presently investigated [408]. For most anatomical locations (with exception of the brain) treatment planning for ultrasound is very challenging since full-wave 3 D simulations are extremely computationally intensive, and thus it is mostly used to optimize or adapt the aperture of US phased arrays to the tumor location or shape [409,410]. Treatment planning for HIFU has to some extent become obsolete because of the use of on-line MR-thermometry for treatment guidance.…”