Hutchinson E B, Buchanan M T, Hynynen K
Massachusetts Institute of Technology, Harvard and MIT Division of Health Sciences and Technology, Cambridge 02139, USA.
Med Phys. 1996 May;23(5):767-76. doi: 10.1118/1.597741.
A 57 element aperiodic linear phased array was designed and constructed to investigate the feasibility of using transrectal ultrasound for the thermal therapeutic treatment of prostate cancer and benign prostatic hyperplasia. A method of reducing grating lobe levels by using optimized random distributions of unequally sized elements is introduced. Using this technique, array periodicity is avoided, making it feasible to use larger elements and hence fewer elements and amplifier channels, while still achieving acceptable power field patterns. Acoustic power field simulations determined that the grating lobe levels associated with selected aperiodic element distributions were approximately 30%-45% less than those associated with periodic element spacing and the same average element width. Or by using aperiodic rather than periodic element distributions, the average element width could be increased by approximately 20%-35% (approximately lambda/4.4), while maintaining a constant grating lobe level. Prior to construction of the 57 element array, the power capabilities of this type of array were demonstrated with a 16 element aperiodic phased array, which delivered over 28 W of acoustical power per cm of array length while focused. The power field patterns produced by the 57 element array closely matched the field patterns predicted by the theoretical model used in the simulations. The array produced acceptable power field patterns for foci at depths up to 5 cm and up to 2 cm off the center axis, in addition to producing multiple foci simultaneously. Based on the power capabilities and field patterns, this aperiodic array design has the potential to be incorporated into a clinical heating device as a means of delivering thermal therapies to the prostate and other target volumes close to body cavities.
设计并构建了一个由57个阵元组成的非周期线性相控阵，以研究经直肠超声用于前列腺癌和良性前列腺增生热疗的可行性。介绍了一种通过使用不等尺寸阵元的优化随机分布来降低栅瓣电平的方法。使用该技术可避免阵列周期性，从而可以使用更大的阵元，进而减少阵元和放大器通道的数量，同时仍能实现可接受的功率场模式。声功率场模拟确定，与选定的非周期阵元分布相关的栅瓣电平比与周期阵元间距和相同平均阵元宽度相关的栅瓣电平低约30%-45%。或者，通过使用非周期而非周期阵元分布，在保持恒定栅瓣电平的同时，平均阵元宽度可增加约20%-35%（约为λ/4.4）。在构建57阵元阵列之前，用一个16阵元的非周期相控阵展示了这种类型阵列的功率能力，该阵列在聚焦时每厘米阵列长度可提供超过28W的声功率。57阵元阵列产生的功率场模式与模拟中使用的理论模型预测的场模式紧密匹配。该阵列除了能同时产生多个焦点外，还能为深度达5cm且偏离中心轴达2cm的焦点产生可接受的功率场模式。基于功率能力和场模式，这种非周期阵列设计有潜力被纳入临床加热设备，作为向前列腺和其他靠近体腔的目标体积输送热疗法的一种手段。
