PROJECT SUMMARY Implantable medical devices are on the rise, both in the US and worldwide. Over 12 million Americans rely on a cardiac or neuromodulation device, and this number increases by 100,000 every year. Roughly 75% of these patients will require an MRI at some point, many multiple times. Yet, the radiofrequency (RF) fields of MRI can interact harmfully with these devices, causing thermal injuries. This restricts MRI access for most. The rise of low-field MRI scanners, operating at 0.55 T and below, offers promise due to reduced costs and siting advantages. However, there's an alarming lack of data on their RF safety. This absence of knowledge is not merely academic; it bears direct, tangible consequences. Our preliminary findings paint a complex picture: some implants in these low-field scanners experience substantially greater RF heating compared to a 1.5T MRI, while others are markedly safer. This disparity signifies not only heightened risks of injury for some patients but also squandered chances for others who might safely access essential imaging. With the FDA's recent endorsement of these scanners, there's an urgent need to generate thorough, evidence-based knowledge about their RF safety, ensuring we fully harness their benefits without jeopardizing patient welfare. In direct response to this need, we propose a to leverage our expertise in MRI computational modeling and safety assessment and our access to state-of-the-art deep brain stimulation (DBS) and cardiovascular implantable electronic devices (CIEDs) to perform a rigorous and unbiased evaluation of RF heating of DBS and cardiac devices during MRI at 0.55 T. Our team, with ten years of experience in MRI safety, is ideally suited to address this urgent requirement swiftly. Over the last three years, we've forged critical alliances with leading implant manufacturers and gained unique access to the designs of the latest low-field systems. This combination of expertise and privileged access allows us to achieve results faster than traditional timelines. In this 3-year R01 project, we will conduct a thorough assessment of RF heating effects for deep brain stimulation (DBS) and cardiac implantable devices during 0.55 T MRI scans. Combined, these devices represent 80% of the active implant market. Our approach will utilize, validate, and implement RF heating test methods from ISO TS 10974—a robust testing procedure honed globally for two decades and now required by the FDA for MR-conditional labeling. Specifically, our objectives are: To create and validate models that consistently forecast RF exposure levels during 0.55 T MRI (Aim 1). To employ these confirmed models to ascertain RF heating of DBS and CIEDs in both adult and pediatric subjects (Aim 2). To formulate tables that anticipate age and device-specific temperature increases in tissue based on imaging landmarks and pulse sequence metrics (Aim 3).