IMSaT, Division of Imaging and Technology School of Medicine. University of Dundee, Dundee, UK.
Section of Radiological Sciences, Department of Biomedicine, Neuroscience and Advanced Diagnostics, University of Palermo, Palermo, Italy.
Acta Radiol. 2021 Jan;62(1):3-11. doi: 10.1177/0284185120914059. Epub 2020 Apr 10.
Magnetic Resonance Imaging (MRI)-guided Focused Ultrasound Surgery (MRgFUS) is a non-invasive thermal ablation method utilizing high-intensity focused ultrasound (HI-FU) energy for tissue ablation under MRI with real-time thermal mapping. Ablating to a dynamic target as in the liver is very challenging, requiring approval. A novel quality-assured liver tumor ablation system has been proposed for clinics. The paper reports the evaluation of conventional and new MR-receiving coils.
To evaluate the suitability of MR coils as part of the MRgFUS treatment system for liver, while simulating breathing motion in pre-clinical settings.
The novel software communicates with the MR scanner and the transducer. To monitor the temperature via proton resonance frequency (PRF) methodology echo planar imaging (EPI) sequence was used while the algorithms of static, static and dynamic tracking were tested with sonications of 100 W for 30 s on tissue-mimicking phantoms. Different coil sets were used to assess the performance of the system for fitness for dynamic thermometry. Finally, in vivo experiments were performed over a porcine model.
Single-loop four-channel Duoflex and Gem coils provided adequate signal-to-noise ratio and contrast with consistent thermal readings. Body array coils showed severe loss of signal in dynamic cases since the integration of tracking algorithm causes low efficiency.
Body array coils are unsuitable for MRgFUS of the liver due to signal loss. The dedicated coil set with a single loop around the FUS transducer combined with four-channel arrays might be the best option for liver treatment using dynamic MRgFUS applications.
磁共振引导聚焦超声手术（MRgFUS）是一种非侵入性热消融方法，利用高强度聚焦超声（HI-FU）能量在磁共振成像下进行组织消融，并实时进行热图绘制。对肝脏等动态目标进行消融极具挑战性，需要获得批准。一种新型的经过质量保证的肝脏肿瘤消融系统已被提出应用于临床。本文报告了传统和新型磁共振接收线圈的评估结果。
评估磁共振线圈作为 MRgFUS 治疗系统的一部分在模拟临床前呼吸运动情况下用于肝脏的适用性。
新型软件与磁共振扫描仪和换能器进行通信。通过质子共振频率（PRF）方法磁共振回波平面成像（EPI）序列监测温度，同时测试了静态、静态和动态跟踪算法，在组织模拟体模上进行了 100 W 持续 30 s 的超声消融。使用不同的线圈套件评估系统的性能是否适合动态测温。最后，在猪模型上进行了体内实验。
单环四通道 Duoflex 和 Gem 线圈提供了足够的信噪比和对比度，具有一致的热读数。体部阵列线圈在动态情况下信号严重丢失，因为跟踪算法的集成导致效率低下。
由于信号丢失，体部阵列线圈不适合肝脏的 MRgFUS 治疗。带有单个环围绕 FUS 换能器并结合四通道阵列的专用线圈套件可能是使用动态 MRgFUS 应用进行肝脏治疗的最佳选择。
