FDA Highlights Safety in MR Environments in Draft Guidance

To reduce possible burn injuries, the FDA is recommending that manufacturers of magnetic resonance-conditional devices assess radio frequency-induced heating in MR environments.

The assessments would be used to support MR-conditional labeling claims, the agency says in draft guidance released June 29.

The guidance addresses multiconfiguration passive medical devices that can conduct electricity and lead to patient injuries during MRI scans. Many commonly used device types fall into this category, including stents, orthopedic devices, external fracture fixation devices and head fixation frames. 

Due to the many possible configurations and combinations for a passive device, it’s nearly impossible to compare RF-induced heating between the various sizes and dimensions.

Active devices, which require internal or external electrical power, are not within the scope of the guidance, the FDA notes. The guidance also does not establish a heating acceptance criterion.

To reduce the number of possible device configurations or combinations “to a manageable number” and assess RF-induced heating risks, the agency recommends the following steps:

• Define and describe the proposed scan conditions, e.g., magnetic field strength, scan area;
• Use animal data, published literature or scientific rationale to establish heating acceptance criterion;
• Define and describe all possible device configurations and combinations in which a device is intended to be used in clinical practice;
• Use a scientific rational or scientific method to create potential worst-case device configurations and combinations for heating assessments;
• Assess the RF-induced heating for each device configuration/combination and within each MR environment for which the device is intended;
• Provide an estimate of the accuracy of the results; and
• Estimate the expected worst-case in vivo heating to demonstrate the safety of the device in the MR environment, particularly if observed in vitro heating exceeds the specified heating acceptance criterion.

The “assessment paradigm” outlined in the guidance would be used in conjunction with the information provided in FDA’s current guidance on Establishing Safety and Compatibility of Passive Implants in the Magnetic Resonance (MR) Environment,” the FDA says.

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