Are 3T MRI Exams Safe For Patients with Pacemakers and ICDs?

 描述(由申请人提供)：所有临床领域的优势都禁止对安装了起搏器和植入性心律转复除颤器(ICD)的患者进行MRI检查。其结果是，出于安全考虑，每年有近200,000名患者放弃临床指示的MRI检查。主要的担忧包括：(1)磁场对设备电子设备的干扰，这可能会导致起搏问题或损坏设备；以及(2)射频(RF)诱导的导线尖端加热，可能会瞬时或不可逆转地损害导线尖端的组织，并抑制起搏。临床证据支持这样一个事实，即当遵循特定的扫描方案时，安装了起搏器和ICD的患者可以在1.5T扫描各种临床适应症，而不会发生严重的不良事件；然而，对安装起搏器和ICD的患者在3T进行MRI扫描的风险知之甚少。这项拟议工作的目标是定义3T MRI检查条件，在这些条件下，安装起搏器或ICD的患者可以安全地完成(3°C导线尖端加热)，和/或可以获得与1.5T下相同检查相当的安全水平。由于信噪比的内在改善，3T MRI检查在临床上常常是首选，这通常会提高空间分辨率和解剖细节的显着性。尽管有这些优势，但对于安装了起搏器和ICD的患者，3T时的MRI检查比1.5T时更严格，这主要是因为人们普遍担心，3T时设备故障和导线尖端发热最有可能更严重。为了实现这一目标，我们将在1.5T和3T的MRI检查中使用多个光纤温度探头直接测量身体起搏器或ICD的导线尖端的温度。其目的是在尽可能接近临床受试者的解剖和组织特征的条件下直接测量铅尖加热。核磁共振测温也将被用来监测远离铅尖的加热情况。实验将包括完整的神经(头部)、胸部(脊柱和心脏)、腹部和膝盖MRI检查，使用标准临床方案，并根据ASTM指南进行15分钟的中级SAR(2W/kg)和高SAR(4W/kg)扫描。类似的实验将在模拟身体起搏器导线配置的组织等效凝胶模体中进行，使用3D打印导线路径固定器。这项工作的公共卫生意义在于，这项工作的结果将定义3T磁共振检查条件与1.5T检查一样安全或更安全，使用的实验条件非常类似于扫描植入起搏器和ICD的人体受试者。其影响将是减轻接受3T或1.5T磁共振检查的心脏起搏器和ICD患者面临的风险。

 DESCRIPTION (provided by applicant): MRI exams for patients with pacemakers and implanted cardioverter defibrillators (ICDs) are contraindicated at all clinical field strengths. A a consequence, nearly 200,000 patients per year forego a clinically- indicated MRI exam due to safety concerns. Principal concerns include: (1) magnetic field interference with the device electronics, which may cause pacing problems or damage the device; and (2) radiofrequency (RF) induced lead-tip heating, which may transiently or irreversibly damage tissue at the lead-tip and inhibit pacing. Clinical evidence supports the fact that patients with pacemakers and ICDs can be scanned at 1.5T for a variety of clinical indications without serious adverse events when specific scanning protocols are followed; however, little is known about the risks associated with MRI scanning of patients with pacemakers and ICDs at 3T. The goal of the proposed work is to define the 3T MRI exam conditions for which a patient with a pacemaker or ICD may be safely completed (<3°C lead-tip heating), and/or may be procured at a level of safety comparable to the same exam at 1.5T. 3T MRI exams are often preferred clinically due to the inherent improvement in SNR, which typically results in improved spatial resolution and conspicuity for anatomical detail. Despite these advantages, MRI exams for patients with pacemakers and ICDs are more strongly contraindicated at 3T than at 1.5T, largely because of prevailing concerns that device malfunction and lead-tip heating are most likely worse at 3T. To accomplish this goal we will, directly measure lead-tip heating at the pacemakers or ICDs lead-tip in cadavers using multiple fiber-optic temperature probes during MRI exams at 1.5T and 3T. The objective is to directly measure lead-tip heating under conditions that mimic, as closely as possible, the anatomic and tissue characteristics of clinical subjects. MRI thermometry will also be used to monitor heating distant from the lead tip. Experiments will include complete neuro (head), thoracic (spine and cardiac), abdominal, and knee MRI exams using standard clinical protocols and 15-minute intermediate SAR (2W/kg) and high SAR (4W/kg) scans per ASTM guidelines. Similar experiments will be performed in tissue equivalent gel phantoms that mimic the cadaveric pacemaker lead configuration using a 3D printed lead-path fixtures. The Public Health Significance is that the results of this work will define the 3T MRI exam conditions that are as safe or safer than a 1.5T exam using experimental conditions that closely mimic scanning human subjects with implanted pacemakers and ICDs. The impact will be to mitigate the risks faced by patients with pacemakers and ICDs undergoing either 3T or 1.5T MRI exams.