Özen Ali Caglar, Silemek Berk, Lottner Thomas, Atalar Ergin, Bock Michael
Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Freiburg, Germany.
Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Magn Reson Med. 2020 Aug;84(2):1048-1060. doi: 10.1002/mrm.28153. Epub 2020 Jan 21.
To dynamically minimize radiofrequency (RF)-induced heating of an active catheter through an automatic change of the termination impedance.
A prototype wireless module was designed that modifies the input impedance of an active catheter to keep the temperature rise during MRI below a threshold, ΔT . The wireless module (MR safety watchdog; MRsWD) measures the local temperature at the catheter tip using either a built-in thermistor or external data from a fiber-optical thermometer. It automatically changes the catheter input impedance until the temperature rise during MRI is minimized. If ΔT is exceeded, RF transmission is blocked by a feedback system.
The thermistor and fiber-optical thermometer provided consistent temperature data in a phantom experiment. During MRI, the MRsWD was able to reduce the maximum temperature rise by 25% when operated in real-time feedback mode.
This study demonstrates the technical feasibility of an MRsWD as an alternative or complementary approach to reduce RF-induced heating of active interventional devices. The automatic MRsWD can reduce heating using direct temperature measurements at the tip of the catheter. Given that temperature measurements are intrinsically slow, for a clinical implementation, a faster feedback parameter would be required such as the RF currents along the catheter or scattered electric fields at the tip.
通过自动改变终端阻抗来动态最小化有源导管的射频（RF）感应加热。
设计了一个原型无线模块，该模块可修改有源导管的输入阻抗，以使磁共振成像（MRI）期间的温度升高保持在阈值ΔT以下。无线模块（MR安全监测器；MRsWD）使用内置热敏电阻或来自光纤温度计的外部数据测量导管尖端的局部温度。它会自动改变导管输入阻抗，直到MRI期间的温度升高最小化。如果超过ΔT，反馈系统会阻断RF传输。
在体模实验中，热敏电阻和光纤温度计提供了一致的温度数据。在MRI期间，当以实时反馈模式运行时，MRsWD能够将最大温度升高降低25%。
本研究证明了MRsWD作为减少有源介入设备RF感应加热的替代或补充方法的技术可行性。自动MRsWD可通过在导管尖端进行直接温度测量来减少加热。鉴于温度测量本质上较慢，对于临床应用，将需要更快的反馈参数，例如沿导管的RF电流或尖端的散射电场。
