Numerical Study on the Possible Scanning Pathways to Optimize Thermal Impacts During Multiple Sonication of HIFU

Findings from numerical investigation of thermal aspects of tissue phantoms subjected to high intensity focused ultrasound (HIFU) during the process of multiple sonications have been presented. Various scanning pathways are chosen to deliver the acoustic energy and to place multiple lesions at the desired locations within the tissue. A new scanning method based on the calculation of the largest distance between any two consecutive lesions is proposed and developed, which can possibly reduce the total treatment time by eliminating the cooling period. This new approach is compared with conventional scanning methods, namely, raster scan, spiral scan from the center outwards and spiral scan from the outside to the center. Various parameters that affect the thermal response of the tissue due to the generation of multiple lesions are defined and studied so that the energy that is given to each spot can be modulated. It is found that modulation of thermal energy provides better control over HIFU exposure and heating time modulation results into a reduced treatment time. The study highlighted the potential advantages of the proposed scanning method vis-a-vis the other conventional approaches. In particular, compared to the other methods, the proposed approach resulted in the realization of almost uniform distribution of thermal energy over the entire ROI leading to almost simultaneous destruction of the affected lesions. The present study can provide the requisite guidance for HIFU-based treatment planning and also highlights the need for optimizing the scanning pathway on the basis of total number of lesions and time parameters.