MRI Technology for Enhanced Radio Frequency Safety

描述（由申请人提供）：这项工作的总体目标是创造一个MRI成像环境，消除心脏起搏器、深部脑刺激器和其他神经刺激器装置接受者射频烧伤的可能性。今天，大约有300万美国人植入了起搏器，这些起搏器通常禁止进行任何形式的头部、胸部或肌肉骨骼MRI扫描。自20世纪80年代以来，最近对1.5T的成像装置接受者进行的临床安全性研究没有发生事故，也没有发生与起搏器相关的死亡事件。深部脑刺激器接受者的指南通常要求头部传输线圈，并且仅在1.5T时使用，但至少有两例在1.0T时发生了MR引起的脑损伤。一般不能确定不良后果并不能证明安全性，因为这些结果不能外推到其他领域的优势；指南与扫描仪功率相关联，报告不一致，MRI系统缺乏基于物理存在的先决条件预测和避免潜在加热条件的强大方法。磁共振扫描仪本身的工程改进可以解决这一问题。这将需要集成能够独立检测或搜索危险共振的电磁安全传感器，能够检测负责加热的引线电流但灵敏度远低于物理加热阈值的MRI RF场测绘方法，以及仅在需要时存储RF功率的分布式发射阵列系统。如果可以检测和成像加热的物理条件，无论场强，患者取向或设备如何，都可以设计射频激励系统来防止加热。本研究的目的是：1)开发一种射频安全预筛选系统，在MRI扫描之前检测危险的相互作用。集成外部传感器系统将开发1.5T，并扩展到3T。这些系统将检测可能产生射频加热的潜在共振设备相互作用，并且可以在患者进入MRI扫描室之前使用。2)开发MRI安全预扫描，以检测和量化低功率MRI扫描的危险相互作用。MRI脉冲序列将检测和量化导电结构上的感应射频电流，并使用这些测量来分级风险，并预测其他序列的潜在加热。3)使用先进的射频传输方法为未来开发更安全的MRI系统。发射阵列激励系统和优化的脉冲序列将最大限度地减少植入设备附近的电磁耦合和射频加热。这将在3T的活体动物模型中进行测试，以表明植入导线上的射频电流可以被消除，同时为成像提供足够均匀的射频场。最终，这项工作将导致一个临床可测试的系统。实现这些目标将大大增加心脏或神经刺激器植入物的广大患者使用MRI的机会，这些患者目前因担心射频加热危险而被拒绝使用。

DESCRIPTION (provided by applicant): The overall goal of this work is to create an MRI imaging environment that eliminates the possibility of RF burns for recipients of cardiac pacemaker, deep brain stimulator, and other neuro-stimulator devices. Today, about 3 million Americans have implanted pacemakers that typically contraindicate any form of head, chest, or muskulo-skeletal MRI scan. Recent clinical safety studies for imaging device recipients at 1.5T have been performed without incident and no related fatalities for pacemakers have occurred since the 1980s. Guidelines for deep brain stimulator recipients typically require head transmit coils and only at 1.5T but at least two MR induced brain injuries have occurred at 1.0T. The general failure to identify adverse outcomes does not prove safety because these results cannot be extrapolated to other field strengths; guidelines are tied to scanner power which is reported inconsistently, and MRI systems lack robust methods of predicting and avoiding potential heating conditions based on physically existing preconditions. Improved engineering of the MR scanner itself can solve this problem. This will require an integration of electromagnetic safety sensors that can independently detect or search for dangerous resonances, MRI RF field mapping methods that can detect lead wire currents responsible for heating but at sensitivities well below physical heating thresholds, and distributed transmit array systems that deposit RF power only where needed. If the physical conditions for heating can be detected and imaged, regardless of field strength, patient orientation, or device, an RF excitation system can be designed to prevent heating. The aims of this research are to: 1) Develop an RF safety prescreen system to detect dangerous interactions before the MRI scan. Integrated external sensor systems will be developed for 1.5T, and extended to 3T. These systems will detect potential resonant device interactions that may produce RF heating and can be used before the patient even enters the MRI scan room. 2) Develop an MRI safety pre-scan to detect and quantify dangerous interactions with a low power MRI scan. MRI pulse sequences will detect and quantify induced RF currents on conductive structures, and use these measurements to grade risk, and predict potential heating for other sequences. 3) Develop safer MRI systems for the future using advanced RF transmission methods. Transmit array excitation systems and optimized pulse sequences will minimize electromagnetic coupling and RF heating near implanted devices. This will be tested in an in vivo animal model at 3T to show that RF currents on an implanted lead can be nulled while providing a sufficiently uniform RF field for imaging. .Ultimately, this work will lead to a clinically testable system. Achieving these goals will substantially increase access to MRI for a broad class of patients with cardiac or neuro-stimulator implants who are currently denied access out of fear of RF heating danger. PUBLIC HEALTH RELEVANCE: Technology to enhance RF safety in MRI scanners- is important to public health because it will enable the 3 million Americans with cardiac pacemakers or deep brain stimulator implants to safely undergo MRI exams without fear of unintended local RF burns. Underutilization of MRI scanners with these patients can be avoided, and the risk of adverse events or unsafe settings can be substantially eliminated.