Purpose: To test the feasibility and efficacy of a percutaneous sonographically guided high-intensity interstitial ultrasound (US) ablation applicator to create "macrolesions" of confluent coagulation in an in vivo pig liver model.
Materials and methods: Eight pigs and an interstitial US ablation applicator were used for this study. Elementary lesions and macrolesions created by the confluence of several elementary lesions were successively analyzed. The first phase of the study was performed by varying the acoustic intensity (AI) to create elementary lesions. The second phase of the study aimed at creating macrolesions in three target zones previously defined in the liver. Mean (+/- SD) maximum and minimum diameters of the macrolesions were calculated.
Results: The elementary lesions created with AIs of 30, 40, and 55 W/cm(2) measured 14.9 mm +/- 3, 19.8 mm +/- 5, and 13.2 mm +/- 3, respectively. The AI retained for the second experimental phase was 40 W/cm(2). Because of the flamelike aspect of the elementary lesions, the macrolesion appeared as a cylinder with crenelated contours. On macroscopic examination, mean maximum diameters of the macrolesions were 28.7 mm +/- 3, 34.1 mm +/- 2, and 27.8 mm +/- 5 and mean minimum diameters of the macrolesions were 14 mm +/- 3, 18.7 mm +/- 2, and 14 mm +/- 3 for the three target zones, respectively. A single major complication, puncture of the gallbladder, occurred in one animal.
Conclusions: A percutaneous sonographically guided interstitial ablation applicator is able to create macrolesions of coagulation in pig liver.