Department of Radiology, LMU University Hospital, LMU Munich, Munich, Germany.
Department of Diagnostic and Interventional Radiology, Heidelberg University Hospital, Heidelberg, Germany.
Eur Radiol Exp. 2024 Aug 14;8(1):92. doi: 10.1186/s41747-024-00479-5.
Interventional magnetic resonance imaging (MRI) can provide a comprehensive setting for microwave ablation of tumors with real-time monitoring of the energy delivery using MRI-based temperature mapping. The purpose of this study was to quantify the accuracy of three-dimensional (3D) real-time MRI temperature mapping during microwave heating in vitro by comparing MRI thermometry data to reference data measured by fiber-optical thermometry.
Nine phantom experiments were evaluated in agar-based gel phantoms using an in-room MR-conditional microwave system and MRI thermometry. MRI measurements were performed for 700 s (25 slices; temporal resolution 2 s). The temperature was monitored with two fiber-optical temperature sensors approximately 5 mm and 10 mm distant from the microwave antenna. Temperature curves of the sensors were compared to MRI temperature data of single-voxel regions of interest (ROIs) at the sensor tips; the accuracy of MRI thermometry was assessed as the root-mean-squared (RMS)-averaged temperature difference. Eighteen neighboring voxels around the original ROI were also evaluated and the voxel with the smallest temperature difference was additionally selected for further evaluation.
The maximum temperature changes measured by the fiber-optical sensors ranged from 7.3 K to 50.7 K. The median RMS-averaged temperature differences in the originally selected voxels ranged from 1.4 K to 3.4 K. When evaluating the minimum-difference voxel from the neighborhood, the temperature differences ranged from 0.5 K to 0.9 K. The microwave antenna and the MRI-conditional in-room microwave generator did not induce relevant radiofrequency artifacts.
Accurate 3D real-time MRI temperature mapping during microwave heating with very low RMS-averaged temperature errors below 1 K is feasible in gel phantoms.
Accurate MRI-based volumetric real-time monitoring of temperature distribution and thermal dose is highly relevant in clinical MRI-based interventions and can be expected to improve local tumor control, as well as procedural safety by extending the limits of thermal (e.g., microwave) ablation of tumors in the liver and in other organs.
Interventional MRI can provide a comprehensive setting for the microwave ablation of tumors. MRI can monitor the microwave ablation using real-time MRI-based temperature mapping. 3D real-time MRI temperature mapping during microwave heating is feasible. Measured temperature errors were below 1 °C in gel phantoms. The active in-room microwave generator did not induce any relevant radiofrequency artifacts.
介入式磁共振成像（MRI）可以提供一个综合的环境，通过基于 MRI 的实时温度测绘来监测能量传递，从而实现肿瘤的微波消融。本研究的目的是通过比较基于 MRI 的温度测绘与光纤温度测量的参考数据，来定量评估三维（3D）实时 MRI 温度测绘在体外微波加热过程中的准确性。
在琼脂基凝胶模型中，使用室内磁共振兼容微波系统和 MRI 测温仪进行了 9 项模型实验。MRI 测量持续 700s（25 个切片；时间分辨率 2s）。通过两个距离微波天线约 5mm 和 10mm 的光纤温度传感器监测温度。将传感器的温度曲线与传感器尖端的单像素感兴趣区（ROI）的 MRI 温度数据进行比较；MRI 测温的准确性评估为均方根（RMS）平均温度差。还评估了原始 ROI 周围的 18 个相邻体素，并选择具有最小温差的体素进行进一步评估。
光纤传感器测量的最大温度变化范围为 7.3K 至 50.7K。最初选择的体素中，RMS 平均温度差的中位数范围为 1.4K 至 3.4K。当评估来自邻域的最小差异体素时，温度差异范围为 0.5K 至 0.9K。微波天线和室内磁共振兼容微波发生器不会引起相关射频伪影。
在凝胶模型中，使用非常低的 RMS 平均温度误差（低于 1K）实现了微波加热过程中精确的 3D 实时 MRI 温度测绘。
在临床基于 MRI 的介入治疗中，准确的基于 MRI 的容积实时温度分布和热剂量监测具有重要意义，预计通过扩大肝脏和其他器官中肿瘤的热（如微波）消融的极限，可以提高局部肿瘤控制和程序安全性。
介入式 MRI 可为肿瘤微波消融提供全面的环境。MRI 可通过基于实时 MRI 的温度测绘来监测微波消融。微波加热过程中实现了 3D 实时 MRI 温度测绘。在凝胶模型中，测量的温度误差低于 1°C。主动室内微波发生器未产生任何相关射频伪影。
