August 5, 2019
On August 1, 2019, the Food and Drug Administration (FDA) released a new draft guidance document for "Testing and Labeling Medical Devices for Safety in the Magnetic Resonance Environment." The draft guidance, when used together with FDA guidance for "Recommended Content and Format of Non-Clinical Bench Performance Testing Information," provides more clarity to the types of consideration that go into testing for safety and compatibility of medical devices during magnetic resonance imaging (MRI).
As emphasized in the new draft guidance, it is important to use a risk-based approach when assessing the hazards associated with MR compatibility of medical devices. The types of risk that should be considered include magnetically induced displacement and torque, radio frequency (RF) heating, gradient field heating, RF-induced and gradient-induced unintended stimulation of tissue, device malfunction and interference with the MRI scanner, and image artifact. The risks should be considered for all "passive" devices (those that function without supply of electrical power) and "active" devices (those that rely on a source of power for functioning). This includes fully implanted devices, non-implanted devices, and partially-implanted devices.
Specific standards do not exist for all of the aforementioned device types but standard test methods for the majority of device types are either under development or at least being considered by the medical standards community. Additionally, some of the test methods that have generally been considered "appropriate" for active devices, for example, may also apply to passive devices. Ultimately, once the risks have been mitigated through testing, modeling, rationale, and combinations thereof, a safety label can be developed. The new guidance provides additional labeling recommendations to help MRI facility staff better understand the risks of imaging.
FDA's specific publication related to MRI safety suggests that FDA will apply increased scrutiny to MRI safety evaluations. Manufacturers can be expected to incorporate the relevant risk management practices into their MRI evaluations, including identification of hazards, test methods to evaluate those hazards, and interpretation of test results in the context of a device's intended use as a risk mitigant.
How Exponent Can Help
Exponent's staff members actively participate in the development of ASTM and ISO standards related to MRI compatibility testing. We have experience identifying risks, developing appropriate acceptance criteria, and executing customized testing based on published standards for all types of devices shown, including passive and active medical devices, fully-implanted, partially-implanted, and non-implanted devices. We use the results from these experiments to recommend safety labeling for our clients.