(a) Schematic drawing of a trisectored tubular ultrasound transducer with internal water cooling. Pictures of (b) TriAD/DC and (c) TriAD/CC applicators constructed with polyimide tubing.
Rotational beam plots of a (top) TriAD/CC applicator and (bottom) TriAD/DC applicator at radial distance. The figure represents the normalized intensity of the ultrasound beam profile of a transducer with all three elements active, measured at a radial depth of . Each sectored element had an active surface area of .
Simulated temperature distributions and thermal lesions created by a TriAD/DC applicator. (a) Different applied powers (9, 6, ) for were used for each sector. (b) was applied to each sector for different activation times (200, 400, ) to control the angular shape of a thermal lesion. (c) Two sectors and (d) one sector active for with applied power.
A maximum temperature controller was used to control the angular shape of simulated thermal lesions with TriAD/DC and TriAD/CC applicators. All three sectors were independently controlled to maximum temperatures of (a) (b) , (c) , , and , or (d) , , and to demonstrate real-time temperature feedback control for shaping a heating pattern. The simulations in the top half of the figure (a), (b) was conducted in perfused tissue and in the bottom half of the figure (c) (d), the perfusion rate was .
Radial measurements of simulated thermal lesions at different maximum control temperatures, treatment times, and tissue perfusions. The median radius of a lesion is plotted with the error bars representing the variation of the radius for each thermal lesion. (a), (b) Simulated thermal lesion radius at moderate tissue perfusion . (c), (d) Power applied to to all three sectors of a trisectored interstitial ultrasound applicator for .
Magnitude and phase images of trisectored interstitial ultrasound applicators inserted into beef muscle tissue in a MR scanner. (a) Images of an applicator with negligible MR susceptibility artifact and (b) the maximum applicator susceptibility artifact seen in this study of about in radius.
MR thermal images of a TriAD/CC temperature distribution in a beef muscle sample. (a) One, (b) two, (c) or three elements were activated with an applied power of per sector for .
Time sequence of a heat with a TriAD/DC applicator in room temperature beef muscle with MR temperature monitoring in the interventional MR. The blank spot in the top right of the heating pattern is due to a strip of fat running through the tissue.
TriAD/CC heating pattern in in vivo canine thigh muscle with two active sectors. The temperature distribution displayed no unheated area between sectors and effective radial penetration. The color seen at the top of the image is due to motion of the skin and adjacent tissue during the procedure.
Time sequence of a heat with a TriAD/DC applicator in in vivo canine thigh muscle with MR temperature monitoring in the interventional MR. The temperature increase contour (orange) corresponds closely with a lethal thermal dose.
Simulated thermal heating distribution from the TriAD/DC and TriAD/CC applicators at a maximum tissue temperatures suitable for hyperthermia. The radius of the contour line was measured with all three sectors active for .
Maximum thermal lesion radius produced by trisectored interstitial ultrasound applicators in ex vivo beef liver tissue. Power was applied to the applicators for .
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