A typical lesion created in a single energy delivery with high intensity focused ultrasound (HIFU) has a cigar-like shape. HIFU has been used for ablation of larger target volumes where a series of ablations can be delivered to conform to a target. The cigar-like shape however prohibits the use in small tissue volumes surrounded by critical structures or in small animals due to the significant disproportion in the lesion length and diameter. We developed Multi-Angle Switched HIFU (MASH) to overcome these limitations. The device consists of 2 spherically-focused ultrasound transducers (f= 2.25MHz, d= 38mm, sf = 51mm) with focal zones crossing each other at a 90 degree angle. This arrangement assures maximum energy deposition to the overlapping volume of the focal zones. The transducers are alternated in their operation to allow heat dissipation from areas outside of the overlapping volume and allow heat conduction from center. A numerical simulation and ex-vivo testing of the device was performed in a phantom and pork liver. The results were very promising and specific applications of the device in the clinic as well as in animal research are currently discussed.
A provisional patent has been filed for the concept of the MASH ablation.
Photographs of sectioned lesions induced with MASH in pig liver. Arrows in axial-lateral cuts (A-D) show the direction of incoming ultrasound beams. A white line indicates a border between axial-lateral cut and the elevation-lateral plane at E.