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建一个MRI成像环境，消除心脏起搏器、脑深部刺激器和其他神经刺激器器械接受者射频灼伤的可能性。今天，大约有300万美国人植入了心脏起搏器，通常禁忌任何形式的头部，胸部或肌肉骨骼MRI扫描。最近在1.5T下对成像设备接受者进行的临床安全性研究没有发生任何事件，自20世纪80年代以来，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发射线圈，并且仅在1.5T下，但在1.0T下至少发生了两起MR诱导的脑损伤。由于这些结果无法外推至其他场强，因此无法识别不良结局的一般失败并不能证明安全性;指南与报告不一致的扫描仪功率有关，并且MRI系统缺乏基于物理存在的前提条件预测和避免潜在加热条件的可靠方法。MR扫描仪本身的改进工程可以解决这个问题。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、能够检测导致发热但灵敏度远低于物理发热阈值的导线电流的MRI RF场标测方法以及仅在需要时存放存款RF功率的分布式发射阵列系统。如果可以检测到发热的物理条件并对其成像，则无论场强、患者方向或器械如何，都可以设计RF激励系统来防止发热。本研究的目的是：1）开发一种射频安全预筛选系统，以在MRI扫描前检测危险的相互作用。 集成外部传感器系统将针对1.5T开发，并扩展到3 T。这些系统将检测可能产生射频加热的潜在共振器械相互作用，甚至可以在患者进入MRI扫描室之前使用。 2)开发MRI安全预扫描，以检测和量化与低功率MRI扫描的危险相互作用。MRI脉冲序列将检测并量化导电结构上的感应射频电流，并使用这些测量值对风险进行分级，并预测其他序列的潜在致热。 3)使用先进的射频传输方法开发更安全的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器械附近的电磁耦合和射频加热。这将在3 T的体内动物模型中进行测试，以证明植入电极导线上的射频电流可以归零，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测试系统。实现这些目标将大大增加目前因担心射频加热危险而被拒绝使用的心脏或神经刺激器植入物患者的MRI访问。 公共卫生相关性：增强MRI扫描仪射频安全性的技术对公共卫生至关重要，因为它将使300万美国人能够安全地接受MRI检查，而不必担心意外的局部射频烧伤。可以避免这些患者对MRI扫描仪的利用不足，并且可以基本消除不良事件或不安全设置的风险。

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.