Silemek Berk, Seifert Frank, Petzold Johannes, Hoffmann Werner, Pfeiffer Harald, Speck Oliver, Rose Georg, Ittermann Bernd, Winter Lukas
Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.
Biomedical Magnetic Resonance, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany.
Magn Reson Med. 2022 Jan;87(1):509-527. doi: 10.1002/mrm.28968. Epub 2021 Aug 16.
Rapid detection and mitigation of radiofrequency (RF)-induced implant heating during MRI based on small and low-cost embedded sensors.
A diode and a thermistor are embedded at the tip of an elongated mock implant. RF-induced voltages or temperature change measured by these root mean square (RMS) sensors are used to construct the sensor Q-Matrix (Q ). Hazard prediction, monitoring and parallel transmit (pTx)-based mitigation using these sensors is demonstrated in benchtop measurements at 300 MHz and within a 3T MRI.
Q acquisition and mitigation can be performed in <20 ms demonstrating real-time capability. The acquisitions can be performed using safe low powers (<3 W) due to the high reading precision of the diode (126 µV) and thermistor (26 µK). The orthogonal projection method used for pTx mitigation was able to reduce the induced signals and temperatures in all 155 investigated locations. Using the Q approach in a pTx capable 3T MRI with either a two-channel body coil or an eight-channel head coil, RF-induced heating was successfully assessed, monitored and mitigated while the image quality outside the implant region was preserved.
Small (<1.5 mm ) and low-cost (<1 €) RMS sensors embedded in an implant can provide all relevant information to predict, monitor and mitigate RF-induced heating in implants, while preserving image quality. The proposed pTx-based Q approach is independent of simulations or in vitro testing and therefore complements these existing safety assessments.
基于小型低成本嵌入式传感器，在磁共振成像（MRI）期间快速检测并减轻射频（RF）诱导的植入物发热。
将一个二极管和一个热敏电阻嵌入细长模拟植入物的尖端。通过这些均方根（RMS）传感器测量的RF诱导电压或温度变化用于构建传感器Q矩阵（Q）。在300MHz的台式测量中以及在3T MRI内，展示了使用这些传感器进行危险预测、监测以及基于并行发射（pTx）的减轻措施。
Q采集和减轻措施可在<20毫秒内完成，证明了实时能力。由于二极管（126μV）和热敏电阻（26μK）的高读取精度，采集可使用安全的低功率（<3W）进行。用于pTx减轻的正交投影方法能够在所有155个研究位置减少感应信号和温度。在具有双通道体线圈或八通道头线圈的pTx兼容3T MRI中使用Q方法时，成功评估、监测并减轻了RF诱导的发热，同时保留了植入物区域外的图像质量。
嵌入植入物中的小型（<1.5mm²）低成本（<1欧元）RMS传感器可提供所有相关信息，以预测、监测并减轻植入物中RF诱导的发热，同时保留图像质量。所提出的基于pTx的Q方法独立于模拟或体外测试，因此补充了这些现有的安全评估。
