P3C-5 Split-Focused Ultrasound for Breast Tumor Thermal Surgery with Multidirectional Heating

This study investigated the feasibility of using split-focused ultrasound transducers with mechanical rotation to do multi-direction heating for breast tumor thermal therapy. The driving frequency, radius of curvature, and side length of the rectangle spherical transducer are 0.5 MHz, 10 cm, and 7 cm, respectively. In order to alleviate the rib heating, the transducer was tilted be 45 degree relative to the muscle/bone interface, and its focal zone was shifted with 6 mm away from the center of the planning target volume (PTV). Based on the multi-focus temporal switching technique, strategies employing single transducer and multiple transducers were both evaluated. As a single transducer was used, the transducer was rotated sequentially to achieve a uniform heating from four planned positions with 90 degree apart. While in multiple ultrasound transducers cases, an appropriate arrangement was designed to have the same configuration of acoustic beams in the single-transducer case. Computer simulations and in vitro phantom had been studied for this ultrasound heating system. The results demonstrated the capacity of this system design; it was able to effectively shorten the treatment time by generating a larger thermal lesion through multi-focus switching and sparing the cooling interval through multidirectional sonications. This study indicated that by appropriate arrangement of a single or multiple split-focused transducers with mechanical rotation, it is very promising to implement multi-direction heating for breast tumor thermal therapy.