Zone III is the area outside of the magnet room that, either because of exposure to magnetic fields or simple proximity to the magnet, should be restricted to only trained MR personnel and successfully screened patients or visitors. Unfortunately, as with many other safe practice guidelines, individual facilities and credentialing bodies are too frequently ignoring this standard.
To protect the MRI equipment and even more important the people in the suite, the four-zone principle was established to tie access restrictions to hazards. In short, the more potential hazards in a space (culminating in the magnet room itself), the greater the access controls to get there. And since the risks aren't limited to just the magnet room, access is to be restricted to areas outside of the magnet room, too.
Unfortunately, many MRI suites fail to provide these zones of access and appropriate access controls. Some believe that a dead bolt on the magnet room door is sufficient. While extra security for the magnet room is never a bad idea, it should not be provided in lieu of access controls for the Zone III area. Even beyond the notion that areas within the MRI suite should be controlled, there is the practical consideration of just how you provide access controls.
MR staff shouldn't carry key chains around the department. Though most keys are only weakly ferromagnetic, the rings and fobs that hold them are frequently highly ferrous and are risks in the magnet room. And just because a metallic object is small, doesn't mean that it isn't a threat.
Objects as small as nail clippers and bobby pins have caused patient injury in MRI suites, and a collection of just a few small barrettes, paper clips, or other ferromagnetic items can throw off a magnet's shim, costing tens of thousands of dollars to correct. Plus, after admonishing patients about the dangers of metal in the MRI suite, it is awfully bad form for technologists to whip out a key ring. So without conventional keyed locks, how do you secure areas within the MRI suite?
Both electronic and mechanical combination locks that don't require keys are available. The problem in many facilities is that the combinations to these locks wind up circulated far wider than originally intended, which defeats the purpose of access control.
Even when deployed with the best of intentions, the combinations too often wind up in the hands of security, transport, housekeeping, maintenance, and other incidental staff that may or may not have appropriate MRI safety training. In fact, combination locks are discouraged for MRI suite access controls in the "ACR White Paper on MR Safety."
Just as an MRI will erase the magnetic stripe on each of your credit cards, most magnetic swipe-card technologies will be rendered useless if the card is taken into the magnet room just once. At one client facility, the MR staff had a reputation for being antisocial because they refused to eat in the cafeteria, but it turned out that they didn't go often simply because they couldn't take advantage of the employee discount. The magnetic stripes on the back of their ID badges were erased daily.
So if facilities should not use keys or combination locks, and can't use magnetic swipe locks, what other options are there?
A number of proximity (prox) cards that work through radiofrequency (RF) transponders are both safe in the MR environment and undamaged by high-strength magnetic fields. RF transponders come in other sizes and shapes that are also safe in MRI suites.
RF transponder systems typically read the "key" when momentarily held in front of a sensor pad, unlocking the door for a programmed length of time. These systems can be integrated with automatic door openers, lights, and any number of other control and assistance systems. RF transponder systems also have the capacity to provide unique codes to each "key," allowing individualized access controls, both by location or by time.
For example, perhaps security has access to the MRI suite after-hours, but not to the magnet room. Perhaps housekeeping staff can only have access to the MRI suite during hours of operation so that they are only there under the supervision of trained MR staff. Even more sophisticated systems can allow greater personalization and access controls through the use of fingerprint reading or other biometrics, but these can be both temperamental and very expensive.
These electronic keying systems can be installed at a single standalone location, or can be networked together providing centralized programming, monitoring, and operation. These systems can be (and in many situations will be required to be) tied in with fire alarm systems or have simple mechanical overrides to guarantee exiting in situations of power outage or building alarm.
The physical mechanism to lock the door often comes in the form of an electric strike, an electronically activated bolt, or magnetic locks. These systems can often be retrofitted to existing doors and frames, or can be incorporated, often invisibly, in newly installed doors. The specific selection of the locking device often must be made in conjunction with the keying system and in conformance to code-mandated exiting requirements.
The simplest of these door control/access systems can cost as little as a few hundred dollars for a single point of access. Larger systems that tie facility-wide keying systems together throughout the building can cost much more.
Every MRI facility with the slightest questions about their four-zone setup or the access controls installed should take this opportunity to review their suite. Since neither cost nor flexibility is a significant roadblock to implementing the access controls called for in the safe practice guidelines, any shortcomings should be both easy to identify and quickly corrected.
By Tobias Gilk
AuntMinnie.com contributing writer
June 7, 2006
Reprinted from www.mri-planning.com by permission of the authors. If you would like more information on any aspect of MR facility design or safety, please contact Robert Junk or Tobias Gilk at Jünk Architects.
Magnet room doors and quench entrapment, May 22, 2006
When MRI throughput means more than revenue, April 11, 2006
ECRI's report on MRI safety, March 28, 2006
Doubling down: Raising the stakes of MRI patient safety, March 9, 2006
Ten questions patients should ask their MRI provider: Is this real or is it hype? February 15, 2006
Copyright © 2006 Jünk Architects, PC