Thermal dose optimization via temporal switching in ultrasoundsurgery

摘要

Temporal switching has been simulated and implemented in vivonexperiments as a method to optimize thermal dose in ultrasound surgery.nBy optimizing the thermal dose over a tissue volume, the peakntemperature is decreased, less average power is expended, and overallntreatment time is shortened. To test this hypothesis, a 16 element,nspherically sectioned array has been constructed for application innultrasound surgery guided by magnetic resonance imaging. A simulationnstudy for the array was performed to determine an optimal treatment fromna set of multiple focus fields. These fields were generated using thenmode scanning technique with power levels determined numerically using andirect weighted gradient search in the attempt to create an optimallynuniform thermal dose over a 0.6×0.6×1.0 cm3ntissue volume. Comparisons of the switched fields and a static multiplenfocus field indicate that the switching technique can lower powernrequirements and decrease treatment time by 20%. More importantly, thenpeak temperature of the sonication was lowered 13°C, thus decreasingnthe possibility of cavitation. The simulated results of the 16 elementnarray were then experimentally tested using MRI to noninvasively monitorntemperature elevations and predict lesion size in rabbit thigh muscle innvivo. In addition, the results show that the switching technique can benless sensitive to tissue inhomogeneities than static field sonicationnwhile creating contiguous necrosis regions at equal average powers