title: In vivo evaluation of a mechanically oscillating dual-mode applicator for ultrasound imaging and thermal ablation.
abstract: 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 five-element dual-mode transducer. After thoroughly characterizing the transducer, tissue response to high-intensity ultrasound was numerically calculated 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 or 27 W/cm (2). Electroacoustic conversion efficiency was maximally 72 +/- 3% and impulse response length was 295 +/- 1.0 ns at -6 dB. The depth of thermal damage measured by gross histology ranged from 10 to 25 mm for 13 insertion sites. For six 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 gray-scale intensity dropped by 7.8 +/- 3.3 dB, and estimated the final lesion depth to an accuracy of 2.3 +/- 2.4 mm. This paper verified that the applicator could induce coagulation necrosis in perfused liver and demonstrated the feasibility of real-time monitoring.
authors.affiliation: Inserm, U556, Lyon, F-69003, France. nrowen@gmail.com
authors.forename: Neil R
authors.initials: NR
authors.lastname: Owen
authors.forename: Guillaume
authors.initials: G
authors.lastname: Bouchoux
authors.forename: Belhassen
authors.initials: B
authors.lastname: Seket
authors.forename: Adriana
authors.initials: A
authors.lastname: Murillo-Rincon
authors.forename: Samir
authors.initials: S
authors.lastname: Merouche
authors.forename: Alain
authors.initials: A
authors.lastname: Birer
authors.forename: Christian
authors.initials: C
authors.lastname: Paquet
authors.forename: Eric
authors.initials: E
authors.lastname: Delabrousse
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Chapelon
authors.forename: Rémi
authors.initials: R
authors.lastname: Berriet
authors.forename: Gérard
authors.initials: G
authors.lastname: Fleury
authors.forename: Cyril
authors.initials: C
authors.lastname: Lafon
mesh_terms: D000818:Animals; D003198:Computer Simulation; D004582:Electronics, Medical; D004867:Equipment Design; D057086:High-Intensity Focused Ultrasound Ablation / Q000295:instrumentation* / Q000379:methods; D008099:Liver / Q000000981:diagnostic imaging* / Q000473:pathology; D009991:Oscillometry; D013552:Swine; D014159:Transducers; D014463:Ultrasonography