Strohbehn J W, Curtis E H, Paulsen K D, Yuan X C, Lynch D R
Thayer School of Engineering, Dartmouth College, Hanover, NH 03755.
Int J Radiat Oncol Biol Phys. 1989 Mar;16(3):589-99. doi: 10.1016/0360-3016(89)90474-4.
One of the systems under investigation for producing hyperthermia noninvasively for treating deep-seated tumors is the annular phased array. This device consists of two rings of eight electromagnetic apertures that are placed concentrically about the long axis of the patient and radiate energy toward the center. Previous theoretical and clinical studies have concentrated primarily on systems where the amplitude and phase of the signal applied to each aperture were the same, and these studies have shown that the system is capable of depositing power deep within the patient. Nevertheless, in many situations the system was not capable of producing desirable temperature distributions in the tumor and normal tissue. In this paper we report on a 2-dimensional theoretical investigation where an optimization routine was used to select the amplitude and phases of each of eight apertures. The optimization procedure and resulting calculations were based on CT scans of patients with tumors. The electrical and thermal properties of the different organs and tissues were taken into account. The optimization routine tried to achieve uniform absorbed power in the tumor region with zero absorbed power outside. Using the optimized amplitudes and phases, the SAR (specific absorption rate, W/kg) was calculated for the array. The results show that in general the optimization procedure was successful in that the power deposited within the tumor volume was increased with less power deposited into normal tissue when compared to the equal amplitude and phase case. This SAR data was then used as the input to a program based on the bioheat transfer equation, which calculated the temperature distribution in the patient model for an assumed set of blood perfusion rates. Depending on the location, size of the tumor, and blood perfusion rates, the improvement in the percentage of the tumor brought to therapeutic temperature varied from 0% to as much as 80%.
正在研究的用于无创产生热疗以治疗深部肿瘤的系统之一是环形相控阵。该设备由两个包含八个电磁孔径的环组成，这些环围绕患者的长轴同心放置，并向中心辐射能量。先前的理论和临床研究主要集中在每个孔径所施加信号的幅度和相位相同的系统上，这些研究表明该系统能够在患者体内深处沉积能量。然而，在许多情况下，该系统无法在肿瘤和正常组织中产生理想的温度分布。在本文中，我们报告了一项二维理论研究，其中使用了一种优化程序来选择八个孔径中每个孔径的幅度和相位。优化程序和所得计算基于肿瘤患者的CT扫描。考虑了不同器官和组织的电学和热学特性。优化程序试图在肿瘤区域实现均匀的吸收功率，而在外部实现零吸收功率。使用优化后的幅度和相位，计算了阵列的比吸收率（SAR，单位：W/kg）。结果表明，总体而言，优化程序是成功的，因为与等幅度和相位情况相比，沉积在肿瘤体积内的功率增加了，而沉积在正常组织中的功率减少了。然后，将该SAR数据用作基于生物热传递方程的程序的输入，该程序针对一组假定的血液灌注率计算患者模型中的温度分布。根据肿瘤的位置、大小和血液灌注率，使肿瘤达到治疗温度的百分比提高幅度从0%到高达80%不等。
