By Tobias Gilk

	Photo courtesy of Metrasens Ltd.

The recent Joint Commission Sentinel Event Alert #38 on MRI accidents, last year's American College of Radiology "ACR Guidance Document for Safe MR Practices: 2007" (Kanal et al., 2007), and a string of MRI safety alerts from the U.S. Food and Drug Administration (FDA) have collectively served to raise the profile of accidents and safety in the MRI realm. While all of the alerts describe many MRI safety principles that have been long-established in the field, the fact that accidents in the MRI environment continue unabated indicate that the approach to interdicting accidents has been less than 100% effective over the last several years.

One of the most common accidents in the MRI environment is that of projectiles or missiles that are magnetically attracted to an MRI magnet, which may commonly be up to 60,000 times the strength of the Earth's own magnetic field. Objects as ubiquitous and benign (outside the effects of the MRI) as chairs, medical gas cylinders, and floor polishers can become magnet-homing missiles with life-threatening force.

Often viewed as inescapable products of probability, projectile accidents have caused interruption to critical MRI services; critically damaged MRI equipment; injured patients, staff, and visitors in the MRI room; and been the source of one documented (and several anecdotal) fatalities. Though much of the contemporary MRI safety guidance is a restatement of long-established best practice guidelines, there is one new technological tool to add to an MRI provider's safety armamentarium, the ferromagnetic detector.

Ferromagnetic detectors (FMD) are distinct from airport-style metal detectors that, justifiably, earned the derision of MRI technologists. Following the highly publicized 2001 projectile fatality, many MRI providers were pushed to install metal detection to help screen MRI patients and visitors. At the time, however, conventional metal detectors used for security screening alarmed not only on the potentially dangerous ferrous metals, which are attracted to magnetic fields, but also alarmed on non-magnetic metals such as aluminum, titanium, and brass — materials that many devices that had been given the "MR Safe" designation were made from. Because of the barrage of false-positive alarms, facilities that deployed these conventional detectors quickly found them to be far more disruptive than helpful and removed them from service.

The same fatality that spurred the well intentioned — but quickly aborted — use of conventional metal detectors also motivated the development of ferromagnetic detectors specifically for use in MRI screening. Marketing of these new FMD products began in 2003, and they have proven very effective as a supplemental screening tool for persons entering the MRI suite.

Last year, the "ACR Guidance Document for Safe MR Practices: 2007" (Kanal et al., 2007), a document widely regarded as the industry metric but not currently enforced under any regulatory or credentialing body, recommended the use of ferromagnetic detection systems as an adjunct to conventional screening. More recently, in spring 2008, The Joint Commission issued its Sentinel Event Alert #38 on MRI accidents. As the ACR did before it, The Joint Commission included a recommendation for screening double-checks including, as an example, the use of FMD screening.

This flurry of attention to MR safety issues has led many MRI providers to take a hard look at their own MR safety provisions. They are evaluating how well they measure up to established practices and how new technologies may enhance their safety. One such institution that undertook this review is the New York Presbyterian Weill Cornell Medical Center (NYP/WC).

New York Presbyterian is one of the MRI safety bellwethers that has deployed FMD at every MRI that they operate. How they reached the decision to deploy the technology may hold lessons for all MRI providers interested in reducing the likelihood of accidents at their facilities.

The Evaluation
As a large institution, New York Presbyterian (NYP) undoubtedly has resources that exceed those of other providers, but at the heart of NYP's decision to evaluate ferromagnetic detection was an interest in improving the level of care provided to their MRI patients. In that regard, their motivation is identical to that of most, if not all, MRI providers.

Having become aware of FMD products via trade shows and conversations with Dr. Emanuel Kanal, FISMRM, FACR, AANG, chair of the ACR's MR Safety Committee and a proponent of the technology, New York Presbyterian's Weill Cornell Medical Center gathered its imaging managers and MRI technologists and discussed the desire to investigate FMD. The hospital invited two of the three FMD manufacturers to demonstrate their products and provide a direct hands-on "show and tell" with radiology administrators, MRI technologists, and the system vendors.

Steve Herrmann, MS, RT, CRA, director of imaging services at New York Presbyterian Weill Cornell Medical Center recounted that technologists who evaluated the products had mixed expectations. "Some thought [ferromagnetic detection] would be Star Trek-like and would find anything, but the technology doesn't work that way," recounts Herrmann. "I mean, there are limits to every technology, but it works. It really works."

But the choice to go forward was based on more than a proof-of-concept. Ferromagnetic detection may someday be as ubiquitous to MRI as toasters are to kitchens, but for Herrmann the decision to deploy the new technology and move forward was supported by a developed confidence in the individual vendors that supported both the acquisition decision-making and the products themselves.

Adoption
Ultimately, the hospital elected to try ferromagnetic detection. The New York Presbyterian Weill Cornell Medical Center, an early and enthusiastic adopter to be sure, currently has FMD systems from two vendors, including hand-held and walk-through versions. What began as an experiment quickly became the MRI department's standard operating procedure and has grown through the NYP system. But as with any new technology, the ferromagnetic detectors and the feedback they provided introduced new disruptions that needed to be worked out.

One surprisingly pervasive complication was found to be the presence of ferromagnetic materials worn and carried by hospital staffers. From underwear underwires to the lanyard clips holding staff ID badges, the everyday clothing worn by MR staffers was — literally — cause for alarm as they passed through the apertures of the ferromagnetic detection portals.

New York Presbyterian's experience echoed the findings a groundbreaking study on ferromagnetic detection conducted at the University of Pittsburgh Medical Center under the direction of Dr. Kanal, which found that nearly half of patients who believed that they had divested themselves of all ferromagnetic materials were, in fact, wearing or carrying magnetic materials.

The feedback provided by these ferromagnetic detection systems is for NYP technologists a welcome failsafe to conventional screening methodologies and has helped prevent accidents including the unintended introduction of a conventional ferromagnetic wheelchair, which was nearly brought into one of their MRI rooms. The technology, as viewed by allied clinical personnel who only sometimes work in the MRI suite, hasn't been as warmly embraced. At the medical center, they continue to reinforce the importance of complete MRI screening for every person for every trip into the magnet room.

Adaptation
To maximize the value of ferromagnetic detection screening systems, the Weill Cornell Medical Center has implemented what some have dubbed the "ferromagnetically naked" protocol. The gist of that risqué mouthful is that MR staffers' new dress code is now as much about what not to wear as what to wear. MR staff members are now required to dress for work in clothing that will allow them to pass through the ferromagnetic detection systems without setting them off. To facilitate this, the Imaging Services department decided to provide scrubs, embroidered with a MR unit logo, for all technologists to wear. Standard hospital-issued ID lanyards were replaced with ones with non-ferromagnetic clips. Footwear, undergarments, jewelry, and accessories that do not trigger the FMD systems are the responsibility of the individual technologist (who would want company-issued underwear, anyway?).

By removing all ferromagnetic material from the MR technologists, any alarm can then be immediately attributed to a real threat object and not an unwanted positive alarm from steel grommets in the technologist's shoe, as an example. Mr. Herrmann knew that the safety enhancements of the ferromagnetic detectors' feedback would be quickly eroded if positive alarms were anticipated, accepted, and ultimately dismissed without consideration.

Though still a work in progress, Weill Cornell's intention is to expand the ferromagnetically naked requirement to include all clinical and personnel (nurses, radiologists, anesthesiologists, cardiologists, etc.) when their patient care responsibilities bring them to the MRI suite. The logistics of this expansion to the "MR irregulars" are proving challenging, but the overall effort has at least raised awareness of the allied clinical staff. The physician may forget to bring an MR-conditional stethoscope to the MRI suite, but the new detectors make it plainly obvious when ferrous contraband is about to enter the MRI room. Whether defiant or sheepish in their response, the allied clinicians cannot remain ignorant of the potential safety consequences of their behavior.

The Unexpected
New York Presbyterian Weill Cornell Medical Center uses GE Healthcare MR systems and, for many MR patients, the hospital prepares them for their exams on one of the MR patient tables — which they are able to undock from the MRI unit — outside the MRI gantry room. Once prepped, the MR staff then wheels the patient into the room, docking the table to the MR gantry for the exam. While the total mass of GE Signa patient table is enough to resist the attractive forces from the superconducting magnet, there are a number of ferromagnetic components, such as wheel bearings, the lift cylinder, and cables, which travel with the table-top into and out of the bore, that are ferromagnetic. In its current configuration, the GE Signa patient tables do trigger alarms on the portal-format ferromagnetic detectors. A collaboration partner with GE Healthcare, New York Presbyterian is currently working with GE to determine how these tables may someday be made to be ferromagnetically naked, too.

GE, unfortunately, isn't the only manufacturer challenged by this new technology. Nearly all MR patient transports, including those from MR manufacturers, make use of some ferromagnetic materials, often in wheel bearings or fasteners that bolt the component parts together. New wholly non-ferromagnetic patient transports are just now being marketed to work in concert with FMD systems. The imaging staff at the medical center now uses highly-localized handheld FMD systems to screen the top aspect of any gurney-bound MR patients, thereby screening just the patient and not the transport (Figure 1).

Figure 1. Hand-held ferromagnetic detector
Courtesy of Mednovus

At NYP/WC and other facilities that use FMD systems to screen MRI patients, the screening tools have reaffirmed that traditional screening methodologies are not 100% effective. Ferromagnetic screenings have caught large and small threat objects, from wheelchairs to pocketknives to hairpins, which were not found by interview methods alone. And though the technology is not currently approved for finding ferromagnetic objects internal to the subject's body, distance from the sensor — not the presence of tissue or bone — is one of the key factors in FMD sensitivity. FMD systems have alarmed on the presence of implants and prostheses, some of which were disavowed by the patient during conventional screening, as an incidental finding to the intended superficial screen.

The Future
At the time of publication, ferromagnetic detection is not a requirement for licensure or accreditation. The Joint Commission, however, is said to be implementing a risk-management program in 2009 that will require accredited providers to assess and plan responses to the risks present at their site using, among other benchmarks, Sentinel Event Alert #38 on MRI accidents. And though it won't have the force of regulation, the civil trial in the wake of the infamous 2001 MRI fatality is expected to be resolved before the end of the year and may well assign individual liability to radiologists and/or technologists, in addition to institutional liability to the hospital and possibly even the MR manufacturer. This changing liability profile may spur an even closer look at all MR safety practices.

Other standards and professional bodies are looking to tools in their arsenal to improve MRI safety and these may include facility design and construction codes, accreditation standards, and new certifications. The next several years are likely to see risk reduction strategies presented from many fronts to address an array of safety issues in the MRI suite. Ferromagnetic detection will be one component of this overall strategy, but may represent the first new safety tool for improving MRI safety in many years.

References

Joint Commission, (2008, February 14). Preventing accidents and injuries in the MRI suite. Sentinel Event Alert #38. Available at http://www.jointcommission.org/SentinelEvents/SentinelEventAlert/
sea_38.html

Kanal, E., Barkovich, A. J., Bell, C., Borgstede, J. P., Bradley, W. G., Froelich, J. W., Gilk, T., et al. (2007). ACR Guidance Document for Safe MR Practices: 2007, AJR, 188, 1 — 27. Available at http://acr.org/SecondaryMainMenuCategories/quality_safety/MRSafety/
safe_mr07.aspx

The United States Food and Drug Administration. New guidelines on MRI safety. Patient Safety News. Available at http://www.accessdata.fda.gov/
scripts/cdrh/cfdocs/psn/transcript.cfm?show=65#7

FDA accident report for MRI projectile fatality http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfMAUDE/
Detail.CFM?MDRFOI__ID=345125