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Focusing of high intensity ultrasound through the rib cage using a therapeutic random phased array.

Bobkova, S*; Gavrilov, L*; Khokhlova, V*; Shaw, A; Hand, J* (2010) Focusing of high intensity ultrasound through the rib cage using a therapeutic random phased array. Ultrasound Med. Biol., 36 (6). pp. 888-906.

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A method for focusing high intensity ultrasound propagating through a rib cage that aims to minimize heating of the ribs whilst maintaining high intensities at the focus (or foci) is proposed and tested theoretically and experimentally. Two approaches, one based on geometric acoustics and the other accounting for diffraction effects associated with propagation through the rib cage, are investigated theoretically. A 2D 1 MHz phased array with 254 randomly distributed elements, tissue mimicking phantoms, and samples of pork rib cages are used in experiments. Intensity distributions and absolute values of the intensity in the plane of ribs and in the focal plane are measured using an infra-red camera. Theoretical and experimental results show that, providing the position of the ribs is known, it is possible to provide adequate focusing through the ribs without overheating them for a single focus and several foci, including steering at ± 10-15 mm off and ± 20 mm along the array axis. Focus splitting due to the periodic spatial structure of ribs is demonstrated both in simulations and experiments. The ability to produce thermal lesions in pork chops placed beyond the rib phantom is also demonstrated. The results suggest that the method is potentially useful for clinical applications of HIFU for which the rib cage lies between the transducer(s) and the targeted tissue.

Item Type: Article
Keywords: Random phased array, HIFU, Rib cage, Bone, Focus, Modeling, Diffraction, Ultrasound ablation, Infra-red camera, Thermocouple
Subjects: Acoustics
Acoustics > Ultrasound
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/4677

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