Effect of the Cavitation Suppression Technique during High-intensity Focused Ultrasound on Liver Tissue

High-intensity focused ultrasound (HIFU) relies on the absorption of ultrasound irradiation to non-invasively cause thermal ablation of a tumor. We developed the cavitation suppression technique (CAST) to minimize the risks of non-target tissue damage during HIFU. This study examined the accurate focusing of the ultrasound beam to achieve precise locational targeting. In excised livers, HIFU was used to ablate specific areas of tissue. Although the theoretical volume of the ablated tissue was 1000 mm3, the volume without CAST use was 2641 ± 671 mm3; using CAST, the volume was 1148 ± 356 mm3. The deviation of the focal points in the direction of the ultrasound transducer, without CAST, was 5.0 ± 1.7 mm, but was reduced to 1.2 ± 1.5 mm when CAST was used. The technique was used to ablate hepatic tumors in rabbits, resulting in the ablated area being clearly demarcated from the adjacent, normal liver tissue. The tumor was completely ablated and necrotized. Thus, the new technique CAST may enable more accurate clinical use as a next-generation HIFU therapy for liver tumors.