Distribution of MR Safety Conditions Across Active Implanted Devices
A Panda*, Y Zhou, S Fahrenholtz, J Yu, E Rand, J Hines, W Sensakovic, Mayo Clinic, Arizona, Scottsdale, AZ
Presentations
SU-H300-IePD-F9-6 (Sunday, 7/10/2022) 3:00 PM - 3:30 PM [Eastern Time (GMT-4)]
Exhibit Hall | Forum 9
Purpose: We summarize the distribution of MR scan conditions of various active MR-conditional implanted devices scanned at our facility over the last one-year period. Specifically, we reviewed specific absorption rate (SAR) and coil selection requirement distribution over a wide variety of MR-conditional devices. The purpose of this abstract is to help guide the physicists supporting MR safety to create standardized MR protocols with low SAR thresholds that can cover a wide range of MR-conditional active implanted devices.
Methods: MR-conditional active implant devices requiring SAR, coil, and time restriction were forwarded by the MR operations team for review by the physics. The physics team documented the scan restrictions in a standard form for recordkeeping and point-of-care guidance. The form was filled out by a qualified medical physicist (QMP) for each device after a detailed review of the device MR-safety manual. Key MR safety scan condition parameters were captured, including field strength, coil restriction, SAR restriction, and scan time limit.
Results: Data was analyzed from 297 patients with active MR-conditional devices. For whole-body SAR, device scan conditions grouped around the threshold values of 0.1, 0.4, 0.8, and 2 W/kg. For average head SAR, the two major threshold values were at 0.2 and 0.6 W/kg. For scans with a contraindicated transmit-receive coil, the maximum whole-body SAR threshold was recorded at 0.3 W/kg.
Conclusion: In absence of standard MR scan condition labeling requirement, MR-conditional active implanted devices tend to have highly variable MR safety conditions. Analysis of data shows there are certain key thresholds for SAR. Building the MR protocols around these thresholds can help physicists create standard low-SAR protocols that can accommodate most patients with active devices and minimize the need for on-the-fly parameter changes and optimizations during the patient scan to meet the safety conditions.
Keywords
Not Applicable / None Entered.
Taxonomy
IM- MRI : Safety, Risk evaluation & control
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