MRI Safety Terminology

MRI SAFETY: THE CONTEXT, NOT THE TERMINOLOGY

OLD TERMINOLOGY

Conditional

Safe

Unsafe

Conditional X

MRI Unsafe

MRI Safe

MRI Compatible

MRI Incompatible

MR Unsafe *

MR Compatible *

MR Safe *

NEW TERMINOLOGY

NEW TERMINOLOGY FROM ASTM:

MR Safe, MR Conditional, and MR Unsafe as defined by ASTM Standard F2503-05 has replaced old MR Terminology (MRI Safe and MRI Compatible) defined in 1997.

*1997, the FDA, Center for Devices and Radiological Health, proposed definitions for the terms MR Safe and MR Compatible

** 2005-2008 ASTM F2503-08 Standard Practice for Marking Medical Devices and Other Items for Safety in the Magnetic Resonance.

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Very few manufacturers during the 1998-2008 frame actually used the FDA recommended terminology and definitions for “MR Safe” and “MR Compatible.” More over, per the FDA, MRI test conditions were supposed to be issued conjunctively with the safety status. In actual practice, if conditions were listed at all, they consisted of indicating the static magnetic field strength, or materials of construction. As a result, instead of becoming simpler, MRI’s already confusing terminology list was increased by the manufacturer’s creating two de facto standard terms.

MagResource MRI Implant Safety Database

Example A – “MRI Safe” (not MR Safe)

Titanium Standard Clip

“Non-ferromagnetic, MRI-safe up to 3 Tesla”

Example B – “MRI Safe” (not MR Safe)

Stents and Catheters

“…all stents and catheters are MRI Safe.”

Example C – “MRI Compatible” (not MR Compatible)

Otologic Cement

.”..is MRI-compatible. Image quality may be impeded in direct vicinity of an implant;…”

Example D – “MRI Compatible” (not MR Compatible)

“... non-ferrous elgiloy valve components provide a completely MRI compatible valve with no artifact.”

MRI Safe and MR Safe differ by only one letter. When this message first appeared on the MagResource website at least one person was quick to point out that it was “misleading and erroneous.” Maybe not! Aside from the obvious addition of the letter “I,” MR Safe and MRI Safe could have the same meaning. Furthermore, as ridiculous as it sounds, sometimes “MR Safe” and “MR Safe” do NOT necessarily have the SAME meaning! Context is everything!

Confusion reigns prior to 1997 when an assortment of terms (sample listed above) was employed to describe implanted medical devices relative to the MRI environment. The FDA, Center for Devices and Radiological Health in 1997 proposed the terms “MR Safe” and “MR Compatible.” FDA definitions for these terms seemed straight forward at the time:

· MR Safe: The device, when used in the MRI environment, has been demonstrated to present no additional risk to the patient or other individual, but it may affect the quality of the diagnostic information.

· MR Compatible: A device shall be considered MR Compatible if it is first MR Safe and has been demonstrated, when used in the MRI environment, to neither significantly affect the quality of the diagnostic information, nor have its operations affected by the MR system.

Implant manufacturers; however, must have had other thoughts in mind! A search of manufacturers’ documentation generated in the years 1998-2008 revealed that the vast majority of manufacturers established their own de facto standard by creating the terms “MRI Safe” and “MRI Compatible” to identify the safety status of their devices, while simultaneously keeping the FDA’s 1997 recommended definitions. As in: