Enhanced thermal ablation via an acoustic vortex with a large focal region

Focused ultrasound ablation provides a truly noninvasive tumor treatment option with clinically proven feasibility and safety. However, the frequently required long treatment duration hinders its clinical applicability. In this work, we compared the thermal ablation induced by conventional focused ultrasound (cFUS), split-focus ultrasound (sFUS), and acoustic vortex (AV) in tissue phantoms containing phase-change nanodroplets and mouse tumors. The results indicated that AV could substantially enhance the thermal ablation efficiency compared with cFUS, which was attributed to the larger focal region in the former. Additionally, the ablation region appeared as a unique cylindrical area with a smaller length-to-width ratio in AV than that in cFUS. Though the efficiency could also be improved in sFUS compared with cFUS, the ablation region was irregular and non-ablated tissues were present. Furthermore, in vivo experiments demonstrated that the tumor volume decreased faster and the mice survived longer after AV treatment compared with cFUS. The cavitation activity was also found to be more intense in AV ablation. The proposed method may solve the general issue of low efficiency often observed in cFUS ablation and further promote the development of other ultrasound treatments.