MR-Safe vs. Non-Ferromagnetc:

By Tobias Gilk

As someone who’s luggage has apparently become a favorite pastime with airport security screeners (you try getting through airport security with forty pounds of magnets in your carry-on), I have a new appreciation for metal detectors and the people who operate them.  However unusual it may be, my box of magnets and assortment of non-ferrous equipment - while they may pique the curiosity of the baggage screeners - aren’t a threat to aviation safety. Apply this to MRI, we have developed an entire classification designating objects as ‘safe’ though, like my box of magnets to the baggage screening device, most MR-Safe objects will light up metal detectors like a Christmas tree.

Along comes the ferromagnetic detector, devices specifically designed to not alert on non-ferromagnetic metals such as aluminum, brass, titanium and non-ferrous blends of stainless steel. These portals and area screeners are supposed to let safe materials and objects pass, and only alert on potentially dangerous objects of different shapes and sizes.  The problem is that many of our MR-Safe devices are held together with bits of steel and will set off even these new detectors that are specifically designed for MRI suites.

The principle of MR-Safe objects is that they can not be drawn into a magnet. If a MR-Safe wheelchair has, for example, a steel rim on a wheel, but the mass of steel isn’t enough that the chair is subject to being moved by a magnet, it is deemed MR-Safe. But only safe at the tested field strength. That wheelchair that is tested MR-Safe for a low-field open MRI isn't necessarily safe when taken into another magnet room. Since diagnostic imaging departments have almost universally snubbed conventional ‘airport style’ metal detectors, the addition of small amounts of strong and economical steel to MR-Safe equipment seemed inconsequential. But the ferrous detector changes this equation.

For the first time in MRI, we have a specific safety tool to aid in the screening of people and devices for missile threat objects. My fear is that these critical devices won’t experience the rapid adoption that they ought to, because they won’t be selective, alerting on only those ferrous materials the staff doesn’t already know about. There is a detection screener capable of this level of selectivity, it’s called the technologist. If, however, we want a device that helps streamline the screening process and enhance patient throughput (not to mention, significantly cut the risks of missile effect accidents), we need to make a couple of changes.

First, no longer will it be acceptable to develop new portable products for the MRI suite that contain ANY ferrous material, when avoidable. These new products, devoid of any steel components, will receive a new designation that will supercede MR-Safe. Perhaps the name for this new class could be 'Ferro-Free' or something equally catchy.  To meet the requirements of this proposed designation, manufacturers and vendors of MRI equipment may need to revise their designs and take advantage of materials such as aluminum, stainless steel, carbon fiber and new high-strength plastics.

Second, MRI facilities should develop policies to eliminate ferrous metals on staff who work within the MRI suite. This may mean requiring staff to wear pocketless scrubs, prohibiting the carrying of cell phones, even scrutiny of personal jewelry. These minor changes, however, will enable the effective use of ferrous-only detection systems and enhance both safety and performance in the MRI suite.

For those manufacturers and vendors of equipment for the MRI suite that aren’t swayed by either the thought of enhanced safety or the prospect of an untapped market, you may want to consider the booming market in transportation security. Think of the convenience of a non-ferromagnetic wheelchair when passing through airport security. After all, people in the screening line don’t need the delay of the 80-year-old woman in the wheelchair clogging up the detectors. They’ll already be frustrated because they’re behind me and my forty pounds of magnets.