Department of Electrical and Computer Engineering, College of Science and Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
IEEE Trans Biomed Eng. 2012 Jan;59(1):95-105. doi: 10.1109/TBME.2011.2162105. Epub 2011 Jul 14.
A system for the realtime generation and control of multiple-focus ultrasound phased-array heating patterns is presented. The system employs a 1-MHz, 64-element array and driving electronics capable of fine spatial and temporal control of the heating pattern. The driver is integrated with a realtime 2-D temperature imaging system implemented on a commercial scanner. The coordinates of the temperature control points are defined on B-mode guidance images from the scanner, together with the temperature set points and controller parameters. The temperature at each point is controlled by an independent proportional, integral, and derivative controller that determines the focal intensity at that point. Optimal multiple-focus synthesis is applied to generate the desired heating pattern at the control points. The controller dynamically reallocates the power available among the foci from the shared power supply upon reaching the desired temperature at each control point. Furthermore, anti-windup compensation is implemented at each control point to improve the system dynamics. In vitro experiments in tissue-mimicking phantom demonstrate the robustness of the controllers for short (2-5 s) and longer multiple-focus high-intensity focused ultrasound exposures. Thermocouple measurements in the vicinity of the control points confirm the dynamics of the temperature variations obtained through noninvasive feedback.
一种用于实时生成和控制多焦点超声相控阵加热模式的系统被提出。该系统采用 1MHz、64 个阵元的阵列和驱动电子设备，能够实现加热模式的精细时空控制。驱动器与在商业扫描仪上实现的实时 2D 温度成像系统集成在一起。温度控制点的坐标是在来自扫描仪的 B 模式引导图像上定义的，同时还定义了温度设定点和控制器参数。每个点的温度由独立的比例、积分和微分控制器控制，该控制器确定该点的焦点强度。最佳多焦点合成用于在控制点生成所需的加热模式。控制器在达到每个控制点的期望温度时，从共享电源动态地在焦点之间重新分配可用功率。此外，在每个控制点实施抗积分饱和补偿，以提高系统的动态性能。在组织模拟体模中的体外实验证明了控制器在短（2-5 秒）和长的多焦点高强度聚焦超声照射下的鲁棒性。在控制点附近进行的热电偶测量证实了通过非侵入式反馈获得的温度变化的动态。
