FDA revises magnetic resonance guidance to reflect updated international standard

The US Food and Drug Administration (FDA) has revised its position on magnetic resonance (MR) with updates to a pair of final guidance documents.

One of the guidance documents covers the testing and labeling of medical devices for safety in the MR environment. The other document addresses premarket notifications for magnetic resonance diagnostic devices (MRDDs). FDA originally issued guidance on MRDDs and safety in the MR environment in 2016 and 2021, respectively, and updated both documents on 10 October 2023.

Neither document has undergone an extensive revision, with most of the content unchanged from the earlier versions. FDA has made more changes to the MRDD guidance than the MR environment text, in part because of the need to update the document to reflect a new edition of the recognized standard on the basic safety and essential performance of magnetic resonance equipment for medical diagnosis.

The fourth edition of the standard redefined the main magnetic field hazard area, a term that describes the space around MR equipment where the static magnetic field is strong enough to cause harm. The International Electrotechnical Commission (IEC) previously recommended restricting access to anywhere with 0.5 mT (a unit of magnetic flux density), but increased the limit to 0.9 mT in its revised standard.

FDA has updated its advice on the controlled access area around MR equipment in line with the revised standard, while leaving manufacturers free to continue to recommend 0.5 mT as “a more conservative limit.” That change is also reflected in the other guidance document, which previously listed 0.5 mT as the definition of the MR environment but now discusses the concept without providing a figure.

The IEC-related change is one of several alterations to the MRDD document that FDA published in 2016. Another change relates to FDA’s stance on the information applicants should provide about the software used in MRDDs. Previously, FDA expressed a “moderate” level of concern about MRDD software and set its documentation requirements accordingly. FDA has removed the line about its level of concern from its guidance. Now, the regulator is advising applicants to provide a “basic documentation level.”

Other changes include the simplification of a section on biocompatibility. Having previously spent several lines discussing its requirements, FDA now states applicants should “address biocompatibility for any patient-contacting materials” and refers readers to another guidance document for more information.

FDA has also revised the introduction to a list of examples of changes to device modifications that may require a 510(k) submission. The updated introduction refers to two other guidance documents on how to decide whether to submit a 510(k) in relation to changes to existing devices and software. FDA has added a footnote about predetermined change control plans, a mechanism that allows manufacturers to make certain changes to devices without submitting a 510(k) filing.

The guidance on testing and labeling medical devices for safety has undergone fewer changes. As well as updating its definition of the MR environment, FDA has deleted a paragraph about assessing the risks posed by metallic medical devices. The revised guidance replaces specific advice with a line that some experimentation may be needed to determine the worst-case device size and configuration for assessing magnetically induced torque.

Testing and Labeling Medical Devices for Safety in the MR Environment

Submission of Premarket Notifications for MRDDs

FDA revises magnetic resonance guidance to reflect updated international standard

Related topics

Recommended content

Welcome to the new RAPS Digital Experience