The New 'MR Safe':
Language Changes For The FDA.

By Tobias Gilk

For years the FDA has been struggling with a vocabulary problem. The current definition of ‘MR Safe’ is limited to objects not getting sucked into the bores of magnets. If a particular ladder, or pump, or wheelchair is determined safe for a 0.35 Tesla open MR, it isn’t necessarily safe in a 3.0 T MRI, or even a 1.5 T. And ‘MR safe’ may have been safe for certain gradients or sequences, but not others. And ‘MR Safe’ may have been deemed safe outside the 50-gauss line, but not inside it. In short, there is nothing definitive about an object being classified as ‘MR Safe’, which has led to tremendous confusion.

There’s nothing about the term ‘MR Safe’ that leads you to believe that there are conditions attached. That and the seemingly absoluteness of the term have led many to misuse the language. That’s all about to change... 

ASTM (formerly the American Society for Testing and Materials, now known solely by their acronym), the body that developed the testing standards for the current ‘MR Safe’ and ‘MR Compatible,’ is now revising their language. The proposed new terminology has three classifications, ‘MR Safe,’ ‘MR Conditional,’ and ‘MR Unsafe.’ 

The proposed new language:

The new ‘MR Safe’ will be a much higher standard and will be, as many have mistakenly been using the current term, absolute. To obtain the new ‘MR Safe’ designation objects must be completely free of all metallic components. It must be completely non-metallic, non-conductive, and not RF reactive. Everything that receives the new ‘MR Safe’ designation must be equally safe at all field strengths, gradients and sequences.

According to Dr. Emanuel Kanal, FACR, who has worked with ASTM and the FDA to develop the new language and standards, “The only way an object with the proposed new ‘MR Safe’ designation could hurt a patient would be if you threw it at them.”

Objects getting the new designation will have to be fabricated very carefully from non-conductive materials such as rubber, plastics, ceramics, select polymers, wood and fiberglass. 

ASTM is also proposing that vendors who can demonstrate that their products are made from accepted non-conductive materials will not have to undergo expensive testing and certification for the new ‘MR Safe’ designation. No amount of scrutiny or testing will improve the MR safety of a rubber ball, so why squander the resources to do so? 

But the bulk of objects, including most contemporary medical implants and devices, will receive the ‘MR Conditional’ designation. This means that the object or device is safe under certain tested conditions, and those conditions should be enumerated on the product, it’s packaging or in the enclosed literature. If the ASTM has its way, this safety standard would apply equally to mop handles as to pacemakers. 

Nearly everything that carries either the current ‘MR Safe’ or ‘MR Compatible’ designations would be switched to ‘MR Conditional’ under the new standard. Operational criteria that currently is explained in the definition of ‘MR Compatible’ would become conditions for use and function under the new ‘MR Conditional’ label.

The final category virtually self-explanatory, ‘MR Unsafe.’ Objects getting this designation will be those known to pose hazards in all MR environments, a ferromagnetic oxygen cylinder, for example. 

Additionally, the ASTM language does away with any reference to magnet interference. This standard is to be exclusively about safety.

Currently this is simply an ASTM proposed standard with no authority, but that won’t last long. ASTM is developing this standard with the cooperation of the FDA who will, upon ASTM’s completion, either reference the standard ‘as is,’ codifying it as an ASTM standard into the body of FDA regulations, or use the ASTM language as a jumping-off point for their own standard.

Irrespective of what road the FDA takes, this revision holds the promise of making the language of MRI safety more coherent, logical and intuitive, which can only serve to improve the application of safety principles.

In addition to identifying the safety of all objects that can be brought into the MRI suite, a proper MRI suite should also provide a secured quaranteen area for MR Conditional and MR Unsafe items. Make sure that your facility has such an area. If it doesn't, feel free to contact us and we will be happy to work with you to develop a proper suite plan.

To learn more about MRI safety and how the principles can be applied at your facility, contact Junk Architects at (816) 472-7722.