MRI Technology For Enhanced Radio Frequency Safety

增强射频安全性的 MRI 技术

• 批准号: 7491504
• 负责人: John M. Pauly
• 金额: $ 41.28万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7491504
• 关键词: Adverse event; American; Artificial cardiac pacemaker; Brain; Brain Injuries; Burn injury; Cardiac; Chest; Class; Clinical; Clinical Research; Condition; Coupling; Deposition; Detection; Development; Device Safety; Devices; Electromagnetics; Elements; Engineering; Ensure; Environment; Event; Failure; Feasibility Studies; Frequencies; Fright; Goals; Guidelines; Hand; Head; Heating; Human; Image; Imaging Device; Implant; Injury; Intervention; Lead; Localized; MRI Scans; Magnetic Resonance Imaging; Magnetism; Maps; Measurement; Measures; Methods; Monitor; Musculoskeletal; Numbers; Outcome; Pacemakers; Patients; Personal Satisfaction; Physiologic pulse; Plants; Protocols documentation; Pulse taking; Radio; Radiofrequency Interstitial Ablation; Rate; Reporting; Risk; Safety; Scanning; Skeletal system; Solutions; Standards of Weights and Measures; Stimulus; Structure; Surface; System; Techniques; Technology; Temperature; Testing; Thermometry; Time; Tissues; Today; Variant; Work; base; deep brain stimulator; density; hazard; image guided intervention; implantable device; improved; in vivo; physical model; preconditioning; prevent; prototype; sensor

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. Moreover, guaranteed RF safety is a necessary requirement for image guided interventions to be performed under MRI. 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. We believe the solutions for RF safe devices lie in improved engineering of the MR scanner itself. 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 the MR thermometry or physical heating thresholds, and distributed transmit array systems that deposit RF power only where needed. If we can detect and image if the physical conditions exist for heating, regardless of field strength, patient orientation, or device, we can create RF excitation systems that prevent heating. Specifically, our aims are to: 1) Develop electromagnetic safety devices external to the patient that prescreen for dangerous resonant conditions, detect wire currents in real time, or inhibit wire resonances. 2) Develop MRI pulse sequences that detect and quantify the presence of RF currents at levels below the sensitivity needed for detection by MR thermometry. 3) Develop transmit array excitation systems with optimized pulse sequences that maintain image quality but prevent electromagnetic coupling and RF heating near implanted devices. Our approach ultimately involves localizing the region of power deposition with transmit array elements, but even with standard transmit coils, independent RF sensors and/or specialized MRI field mapping methods will give a quantifiable and objective basis for determining if an RF hazard can exist. Achieving these goals will substantially increase access to MRI for a broad class of patients with cardiac or neurostimulator implants who are currently denied access out of fear of RF heating danger.

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，以消除心脏起搏器，深脑刺激器和其他神经刺激器件的受体RF燃烧的可能性。此外，保证的RF安全是在MRI下执行图像指导干预措施的必要要求。如今，约有300万美国人植入了起搏器，这些起搏器通常会禁忌任何形式的头部，胸部或穆斯库洛 - 骨骼MRI扫描。对于1.5T进行了成像设备受体的最新临床安全研究，没有发生任何事件，并且自1980年代以来就没有发生过起搏器的相关死亡。深脑刺激器接受者的指南通常需要头部发射线圈，仅在1.5T下，但至少有两次MR诱导的脑损伤发生在1.0T时。总体上无法识别不良结果并不能证明安全性，因为这些结果不能推断到其他现场优势。指南与扫描仪的功率相关，该指南不一致地报道，MRI系统缺乏强大的方法来预测和避免基于物理上现有的先决条件来预测和避免潜在的加热条件。我们认为，RF安全设备的解决方案在于改进了MR Scanner本身的工程。这将需要整合电磁安全传感器，这些安全传感器可以独立检测或寻找危险的共振，MRI RF场映射方法可以检测到负责加热的铅线电流，但在敏感性下，敏感性远低于MR温度或物理加热阈值，并分布了仅在需要的地方存储RF电源的发射阵列系统。如果我们可以检测和图像是否存在用于加热的物理条件，无论野外强度，患者取向或设备如何，我们都可以创建防止加热的RF激发系统。具体而言，我们的目的是：1）开发预先筛查危险共振条件的患者外部电磁安全设备，实时检测导线电流或抑制电线谐振。 2）开发MRI脉冲序列，以低于MR温度测定度所需的灵敏度的水平检测和量化RF电流的存在。 3）开发具有优化脉冲序列的发射阵列激发系统，可维持图像质量，但可以防止电磁耦合和植入设备附近的RF加热。我们的方法最终涉及将功率沉积区域与发射阵列元件进行定位，但是即使使用标准发射线圈，独立的RF传感器和/或专门的MRI场映射方法，也将为确定RF危害是否存在。实现这些目标将大大增加对心脏或神经刺激植入物的大量患者的MRI访问权限，这些患者目前因担心RF加热危险而被拒绝使用。