Owen N, Bouchoux G, Seket B, Murillo-Rincon A, Merouche S, Birer A, Paquet C, Delabrousse E, Chapelon J, Berriet R, Fleury G, Lafon C
In Vivo Evaluation of a Mechanically-Oscillating Dual-Mode Interstitial Applicator for Ultrasound Imaging and Thermal Ablation. [JOURNAL ARTICLE]
IEEE Trans Biomed Eng 2009 Jun 2.
Unresectable liver tumors are often treated with interstitial probes that modify tissue temperature, and efficacious treatment relies on image guidance for tissue targeting and assessment. Here we report the in vivo evaluation of an interstitial applicator with a mechanically-oscillating 5-element dual-mode transducer. After thoroughly characterizing the transducer, tissue response to high-intensity ultrasound was calculated numerically to select parameters for experimentation in vivo. Using perfused porcine liver, B-mode sector images were formed before and after a 120 s therapy period, and M-mode imaging monitored the therapy axis during therapy. The time-averaged transducer surface intensity was 21 W/cm2 or 27 W/cm2. Electro-acoustic conversion efficiency was maximally 723% and impulse response length was 2951.0 ns at -6 dB. The depth of thermal damage measured by gross histology ranged from 10 mm to 25 mm for 13 insertion sites. For 6 sites, M-mode data exhibited a reduction in gray scale intensity that was interpreted as the temporal variation of coagulation necrosis. Contrast ratio analysis indicated that the intensity dropped by 7.83.3 dB and estimated the final lesion depth to an accuracy of 2.32.4 mm. This work verified that the applicator could induce coagulation necrosis in perfused liver, and demonstrated the feasibility of real-time monitoring.
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