Abstract：
Magnetic Resonance (MR) thermometry is used for the monitoring of MR-guided microwave ablations (MWA), and for the intraoperative evaluation of ablation regions. Nevertheless, the accuracy of temperature mapping may be compromised by electromagnetic interference emanating from the microwave (MW) generator. This study evaluated different setups for improving magnetic resonance imaging (MRI) during MWA with a modified MW generator. MWA was performed in 15 gel phantoms comparing three setups: The MW generator was placed outside the MR scanner room, either connected to the MW applicator using a penetration panel with a radiofrequency (RF) filter and a 7 m coaxial cable (Setup 1), or through a waveguide using a 5 m coaxial cable (Setup 2). Setup 3 employed the MW generator within the MR scan room, connected by a 5 m coaxial cable. The coaxial cables in setups 2 and 3 were modified with custom shielding to reduce interference. The setups during ablation (active setup) were compared to a reference setup without the presence of the MW system. Thermometry and thermal dose maps (CEM43 model) were compared for the three configurations. Primary endpoints for assessment were signal-to-noise ratio (SNR), temperature precision, Sørensen-Dice-Coefficient (DSC), and RF-noise spectra. Setup 3 showed highly significant electromagnetic interference during ablation with a SNR decrease by -60.4%±13.5% (p<0.001) compared to reference imaging. For setup 1 and setup 2 no significant decrease in SNR was measured with differences of -2.9%±9.8% (p=0.6) and -1.5%±12.8% (p=0.8), respectively. SNR differences were significant between active setups 1 and 3 with -51.2%±16.1% (p<0.001) and between active setups 2 and 3 with -59.0%±15.5% (p<0.001) but not significant between active setups 1 and 2 with 19.0%±13.7% (p=0.09). Furthermore, no significant differences were seen in temperature precision or DSCs between all setups, ranging from 0.33 °C ± 0.04 °C (Setup 1) to 0.38 °C ± 0.06 °C (Setup 3) (p=0.6) and from 87.0%±1.6% (Setup 3) to 88.1%±1.6% (Setup 2) (p=0.58), respectively. Both setups (1 and 2) with the MW generator outside the MR scanner room were beneficial to reduce electromagnetic interference during MWA. Moreover, provided that a shielded cable is utilized in setups 2 and 3, all configurations displayed negligible differences in temperature precision and DSCs, indicating that the location of the MW generator does not significantly impact the accuracy of thermometry during MWA.
摘要：
磁共振（MR）测温法用于监测MR引导的微波消融（MWA），以及消融区域的术中评估。然而，温度映射的准确性可能会受到微波(MW)发生器发出的电磁干扰的影响。这项研究评估了使用改良的MW发电机在MWA期间改善磁共振成像（MRI）的不同设置。MWA在15个凝胶体模中进行，比较三个设置：MW发生器放置在MR扫描仪室之外，使用带有射频(RF)滤波器的穿透面板和7m同轴电缆(设置1)连接到MW施加器,或通过使用5m同轴电缆的波导（设置2）。设置3在MR扫描室内使用了MW发电机，由5米同轴电缆连接。设置2和3中的同轴电缆用定制屏蔽修改以减少干扰。将消融期间的设置(主动设置)与不存在MW系统的参考设置进行比较。比较了三种配置的测温和热剂量图（CEM43模型）。评估的主要终点是信噪比(SNR)，温度精度,Sørensen-Dice-Coefficient(DSC),和射频噪声频谱。设置3在消融期间显示高度显著的电磁干扰,与参考成像相比,SNR降低-60.4%±13.5%(p<0.001)。对于设置1和设置2，信噪比没有显著下降，差异为-2.9%±9.8%(p=0.6)和-1.5%±12.8%(p=0.8)。分别。活动设置1和3之间的SNR差异显著,为-51.2%±16.1%(p<0.001),活动设置2和3之间的SNR差异显著,为-59.0%±15.5%(p<0.001),但活动设置1和2之间的SNR差异不显著,为19.0%±13.7%(p=0.09)。此外，在所有设置之间的温度精度或DSC没有显著差异，范围从0.33°C±0.04°C(设置1)到0.38°C±0.06°C(设置3)(p=0.6)和从87.0%±1.6%(设置3)到88.1%±1.6%(设置2)(p=0.58),分别。在MR扫描仪室外部使用MW发电机的两种设置（1和2）都有利于减少MWA期间的电磁干扰。此外，如果在设置2和3中使用屏蔽电缆，则所有配置在温度精度和DSC方面的差异可忽略不计，表明MW发电机的位置不会显著影响MWA期间测温的准确性。
