Department of Radiation Oncology, Erasmus MC-Cancer Institute, University Medical Center Rotterdam, 3015 GD Rotterdam, The Netherlands.
EM4C&C Laboratory, Center for Care & Cure Technology Eindhoven (C3Te), Department of Electrical Engineering, Eindhoven University of Technology, 5612 AZ Eindhoven, The Netherlands.
Sensors (Basel). 2020 May 22;20(10):2946. doi: 10.3390/s20102946.
The potential of MR thermometry (MRT) fostered the development of MRI compatible radiofrequency (RF) hyperthermia devices. Such device integration creates major technological challenges and a crucial point for image quality is the water bolus (WB). The WB is located between the patient body and external sources to both couple electromagnetic energy and to cool the patient skin. However, the WB causes MRT errors and unnecessarily large field of view. In this work, we studied making the WB MRI transparent by an optimal concentration of compounds capable of modifying T 2 * relaxation without an impact on the efficiency of RF heating. Three different T 2 * reducing compounds were investigated, namely CuSO 4 , MnCl 2 , and Fe 3 O 4 . First, electromagnetic properties and T 2 * relaxation rates at 1.5 T were measured. Next, through multi-physics simulations, the predicted effect on the RF-power deposition pattern was evaluated and MRT precision was experimentally assessed. Our results identified 5 mM Fe 3 O 4 solution as optimal since it does not alter the RF-power level needed and improved MRT precision from 0.39 ∘ C to 0.09 ∘ C. MnCl 2 showed a similar MRT improvement, but caused unacceptable RF-power losses. We conclude that adding Fe 3 O 4 has significant potential to improve RF hyperthermia treatment monitoring under MR guidance.
磁共振测温（MRT）的潜力促进了磁共振兼容射频（RF）热疗设备的发展。这种设备集成带来了重大的技术挑战，而图像质量的关键是水囊（WB）。WB 位于患者身体和外部源之间，用于耦合电磁能并冷却患者皮肤。然而，WB 会导致 MRT 误差和不必要的大视野。在这项工作中，我们研究了通过能够在不影响 RF 加热效率的情况下改变 T 2 *弛豫的最佳化合物浓度使 WB 对 MRI 透明。研究了三种不同的 T 2 *降低化合物，即 CuSO 4 、MnCl 2 和 Fe 3 O 4 。首先，测量了在 1.5 T 下的电磁特性和 T 2 *弛豫率。接下来，通过多物理场模拟，评估了对 RF 功率沉积模式的预测影响，并通过实验评估了 MRT 精度。我们的结果确定了 5 mM Fe 3 O 4 溶液为最佳选择，因为它不会改变所需的 RF 功率水平，并将 MRT 精度从 0.39 ∘ C 提高到 0.09 ∘ C。MnCl 2 显示出类似的 MRT 改善，但导致不可接受的 RF 功率损失。我们得出结论，添加 Fe 3 O 4 具有显著改善在 MR 引导下进行 RF 热疗治疗监测的潜力。
