Abstract

Purpose: Thermal intervention is a potent sensitizer of cells to chemo- and radiotherapy in cancer treatment. Glioblastoma multiforme (GBM) is a potential clinical target, given the cancer’s aggressive nature and resistance to current treatment options. The annular phased array (APA) technique employing electromagnetic waves in the radiofrequency (RF) range allows for localized temperature increase in deep seated target volumes (TVs). Reports on clinical applications of the APA technique in the brain are still missing. Ultrahigh field magnetic resonance (MR) employs higher frequencies than conventional MR and has potential to provide focal temperature manipulation, high resolution imaging and noninvasive temperature monitoring using an integrated RF applicator (ThermalMR). This work examines the applicability of RF applicator concepts for ThermalMR of brain tumors at 297 MHz (7.0 Tesla).

Methods: Electromagnetic field (EMF) simulations are performed for clinically realistic data based on GBM patients. Two algorithms are used for specific RF energy absorption rate based thermal intervention planning for small and large TVs in the brain, aiming at maximum RF power deposition or RF power uniformity in the TV for 10 RF applicator designs.

Results: For both TVs , the power optimization outperformed the uniformity optimization. The best results for the small TV are obtained for the 16 element interleaved RF applicator using an elliptical antenna arrangement with water bolus. The two row elliptical RF applicator yielded the best result for the large TV.

Discussion: This work investigates the capacity of ThermalMR to achieve targeted thermal interventions in model systems resembling human brain tissue and brain tumors.

 抽象的

目的：热干预是癌症治疗中细胞对化疗和放疗的有效敏化剂。鉴于多形性胶质母细胞瘤 (GBM) 的侵袭性和对当前治疗方案的抵抗力，它是一个潜在的临床靶点。环形相控阵 (APA) 技术采用射频 (RF) 范围内的电磁波，可实现深部目标体积 (TV) 的局部温度升高。目前仍缺乏 APA 技术在大脑中的临床应用的报道。超高场磁共振 (MR) 采用比传统 MR 更高的频率，并且有潜力使用集成射频施加器 (ThermalMR) 提供焦点温度操纵、高分辨率成像和无创温度监测。这项工作检验了射频涂抹器概念在 297 MHz（7.0 特斯拉）下对脑肿瘤 ThermalMR 的适用性。

方法：对基于 GBM 患者的临床真实数据进行电磁场 (EMF) 模拟。两种算法用于针对大脑中的小型和大型电视进行基于特定射频能量吸收率的热干预规划，旨在为 10 个射频施加器设计实现电视中的最大射频功率沉积或射频功率均匀性。

结果：对于两台电视，功率优化优于均匀性优化。小型电视的最佳效果是通过使用带水团的椭圆形天线布置的 16 元件交错射频施加器获得的。两排椭圆形射频涂抹器为大型电视带来了最佳效果。

讨论：这项工作研究了 ThermalMR 在类似于人类脑组织和脑肿瘤的模型系统中实现有针对性的热干预的能力。