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SonoKnife: Feasibility of a line-focused ultrasound device for thermal ablation therapy
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10.1118/1.3601017
/content/aapm/journal/medphys/38/7/10.1118/1.3601017
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/38/7/10.1118/1.3601017

Figures

Image of FIG. 1.
FIG. 1.

Schematic diagrams of a SonoKnife transducer with a reference frame. (a) a perspective 3D view. (b) Cross-sectional view in which the length of the cylinder (L) extends perpendicularly to the plane of the paper in the y direction.

Image of FIG. 2.
FIG. 2.

(a) For modeling purposes, the cylindrical surface of the simulated SonoKnife transducer was composed of an array of small rectangles whose dimensions are comparable to the wavelength. (b) Photograph of the prototype PZT-8 ultrasound transducer used in experiments with an operating frequency of 3.5 MHz, a radius of curvature (R) of 60 mm, a width (r) of 60 mm, and a length (L) of 30 mm. The mount was machined out of Plexiglas.

Image of FIG. 3.
FIG. 3.

Simulated (a, c, and e) and measured (b, d, and f) pressure distributions on the central y–z plane (x = 0), central z–x plane (y = 0) and central y–x plane (z = 60 mm). The frequency was that of the SonoKnife prototype, 3.5 MHz. All other parameters had nominal values (Table I). Both the simulated and measured pressure distributions were self-normalized. See Fig. 1 for the reference frame.

Image of FIG. 4.
FIG. 4.

Peak pressure amplitude, peak intensity, average intensity, and acoustic edge dimensions in the x, y, and z directions plotted as a function of excitation frequency f. Nominal parameter values in Table I were used except for the excitation frequency, which was varied from 0.5 to 5.0 MHz.

Image of FIG. 5.
FIG. 5.

Peak pressure amplitude, peak intensity, average intensity, and the acoustic edge in the x, y, and z directions plotted as the function of the radius of the curvature R. Nominal parameter values in Table I were used except for the radius of curvature R, which was varied from 40 to 80 mm with an interval 10 mm.

Image of FIG. 6.
FIG. 6.

Peak pressure amplitude, peak intensity, average intensity, and the acoustic edge in the x, y, and z directions plotted as a function of aperture size r. Nominal parameter values in Table I were used except for the aperture size r, which was varied from 40 to 80 mm with an interval 10 mm.

Image of FIG. 7.
FIG. 7.

Peak pressure amplitude, peak intensity, average intensity, and the acoustic edge in the x, y, and z directions plotted as the function of transducer to skin distance d. Nominal parameter values in Table I were used except for the transducer to skin distance d, which was varied from 10 to 50 mm with an interval of 10 mm.

Image of FIG. 8.
FIG. 8.

Focal plane temperature and thermal dose distributions on the central y–z plane (x = 0) after 20 s of static sonication. Nominal parameter values were used. Note that in 9(b) the scales were changed to zoom in into the ablation zone. The three iso-contours in 9(b) are the 10 (outer), 100 and 240 (inner) EM43.

Image of FIG. 9.
FIG. 9.

Temperature and thermal dose distributions on (a) the central z–x plane (y = 0), (b) a y–x plane (z = 60 mm), and (c) a y–z plane (x = 13.2 mm) after step-scanning the acoustic edge in the x direction from −15 to 15 mm. The scanning step was 1.25 mm for a total of 24 steps. For scanning steps 1–3, 4–6, and 7–24, the power-on times were 5.8, 5.0, and 4.15 s/step, respectively. The power-off time in-between sonications was 30 s; consequently, the time to complete the entire scan was 797 s. Nominal parameter values were used except for: the emittance was equal to 6 W/cm3, Wb was set to zero at points that reached 240 EM43, and the skin temperature was held at 22 °C to simulate forced cooling. The contours shown represent the cumulative 10 (blue), 100 (black), and 240 (red) EM43 thermal isodoses after the scan was completed. In (b) only two isodose contours are plotted for clarity.

Image of FIG. 10.
FIG. 10.

Photographs of lesions created by the SonoKnife prototype inside gel phantoms. The sonications were for 20 s for an acoustic power of 120 W (no scanning). The line-focus was positioned approximately at 1.5 cm under the phantom surface. Results for two different phantoms are shown, one was cubical (a, c, e) and one cylindrical (b, d, f). (a) and (b) are beam’s eye view photographs (line-of-sight along the z direction). In (c) and (d) the line-of-sight was along the y direction, showing the projected thickness of the lesion across the acoustic edge. In (e) and (f) the line-of-sight was along the x direction, showing the projected length of the lesion along the acoustic edge.

Image of FIG. 11.
FIG. 11.

Photographs of thermal ablation lesions created by the static SonoKnife prototype in porcine liver ex vivo. Two different lesions are shown, one in (a) and (b), and the other in (c) and (d). The acoustic frequency was 3.5 MHz. The sonications used an acoustic power of 108 W for 30 s aimed at 1.5 cm deep and for 20 s aimed at 2 cm deep for the first and second samples, respectively. In (a) and (c) it can be seen the samples were cut to reveal the lesions in the y–z planes shown in (b) and (d). The yellow arrows denote the direction of acoustic propagation.

Tables

Generic image for table
TABLE I.

Nominal parameter values.

Generic image for table
TABLE II.

Acoustic and thermal properties of water and muscle.

Generic image for table
TABLE III.

Peak pressure amplitude, peak intensity, average intensity, the size of the acoustic edge in the x, y, and z directions for a SonoKnife transducer and a spherical-section transducer with the same radiating surface area and emittance.

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/content/aapm/journal/medphys/38/7/10.1118/1.3601017
2011-06-30
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: SonoKnife: Feasibility of a line-focused ultrasound device for thermal ablation therapy
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/38/7/10.1118/1.3601017
10.1118/1.3601017
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