To guard against accidents, injuries, or damage to MR systems, the general and immediate areas associated with the scanner (also referred to as the MR environment) must have supervised and controlled access. Supervised and controlled access involves having MR safety-trained personnel present at all times during the operation of the facility to ensure that no unaccompanied or unauthorized individuals are allowed to enter the MR environment.
The MR safety-trained personnel are responsible for performing comprehensive screening of patients and other individuals before allowing them to enter the MR system room. The Institute for Magnetic Resonance Safety, Education, and Research recently developed new screening forms for patients and individuals as well as explicit instructions for conducting screening procedures (www.IMRSER.org).
It is also necessary to educate everyone who needs to enter the MR environment on a regular or intermittent basis (e.g., custodial workers, transporters, security personnel, firefighters, nurses, anesthesiologists, etc.) regarding the potential hazards related to the powerful magnetic field of the MR system. Unfortunately, even with proper MR safety procedures in place, many individuals and patients have inadvertently "wandered" unattended into the MR environment, and these situations have resulted in disastrous consequences.
To help control access to the MR environment, the area must be clearly demarcated and labeled with prominently displayed signs making all individuals and patients aware of the risks associated with the MR system. The content of these signs is particularly important, but the information shown on most signs currently in use is out-of-date, erroneous, or not displayed prominently enough. Therefore, new signs with revised content and new information were designed recently to promote a safe MR environment.
THE OLD WARNING SIGN
The sign that used at most MR centers in the U.S. has the following information:
WARNING
STRONG MAGNETIC FIELD
NO PACEMAKERS
NO METALLIC IMPLANTS
NO NEUROSTIMULATION SYSTEMS
NO LOOSE OBJECTS
Obviously, given the present state of knowledge pertaining to MR safety, much of this information is outdated or simply incorrect. In fact, according to the FDA document, Guidance for the Submission Of Premarket Notifications for Magnetic Resonance Diagnostic Devices (issued November 14, 1998), Attachment B, "The controlled access area should be labeled 'Danger -- High Magnetic Field' at all entries."
This FDA document also indicates, "Operators should be warned by appropriate signs about the presence of magnetic fields and their force and torque on magnetic materials, and that loose ferrous objects should be excluded."
THE NEW DANGER SIGN
Therefore, in consideration of the above, the old warning sign was recently revised and updated to include the guidance from the FDA as well as the most current findings for MR safety, especially with regard to implanted objects. Because the term "warning," for example, does not convey the importance of a situation that may not only be potentially hazardous, but has already been responsible for serious injuries and deaths, the newly revised sign now states (Figure 1A):
DANGER!
Additionally, to inform everyone about the powerful magnetic field associated with the MR system, especially individuals unacquainted with MR technology, the following information is prominently shown on this new sign:
RESTRICTED ACCESS
STRONG MAGNETIC FIELD
THE MAGNET IS ALWAYS ON!
In addition to cardiac pacemakers, implantable cardioverter defibrillators (or ICDs) are also potentially hazardous for patients and individuals in the MR environment. Therefore, this information is included on the new sign. Because recently published reports have indicated that certain neurostimulation systems, in contrast, are safe for patients undergoing MR procedures if highly specific guidelines are followed (Rezai et al 2002; Finelli et al 2002), the statement regarding neurostimulation systems was deleted to avoid undue confusion.
Recent articles in the peer-reviewed literature have reported that many types of metallic implants are actually safe for patients undergoing MR procedures. Comprehensive information for over 1100 implants, devices, and other objects is readily available to all MR healthcare professionals in a recently published textbook (Shellock, 2003) and online at www.MRIsafety.com, including information for more than 150 implants and devices tested at 3T. The revised sign clarifies this information, and individuals and patients are informed to consult MRI professionals with are any questions (Figure 1B):
Persons with certain metallic, electronic, magnetic, or mechanical implants, devices, or objects may not enter this area. Serious injury may result.
Do not enter this area if you have any question regarding an implant, device, or object. Consult the MRI Technologist or Radiologist.
Finally, the statement, "NO LOOSE OBJECTS" on the current "warning" sign is rather simplistic and does not address other aspects of concern with respect to bringing potentially problematic items into the MR environment. Accordingly, the new sign states:
Objects made from ferrous materials must not be taken into this area. Serious injury or property damage may result. Electronic objects such as hearing aids, cell phones, and beepers may also be damaged.
This new sign is more prominent, the term "danger" rather than "warning" is used, and the overall content is more accurate with respect to current MR safety information. A Spanish language version of this sign has also been created.*
ADDITIONAL NEW SIGNS
Two other danger signs were created to help control access to the MR environment (Figures 2 and 3). One sign states:
DANGER!
RESTRICTED ACCESS
STRONG MAGNETIC FIELD
This Magnet is Always On!
NO ENTRY BY UNAUTHORIZED
OR UNACCOMPANIED INDIVIDUALS
AND PATIENTS
The intent of this sign is to prevent the inadvertent entry of individuals and patients into the MR environment.
Interestingly, many individuals fail to realize that the MR system's static magnetic field is always on. In fact, investigations of various accidents that involved relatively large ferromagnetic objects like oxygen cylinders, chairs, IV poles, and wheelchairs revealed that the offending hospital personnel thought that the powerful magnetic field was activated only during the MR procedure. Therefore, a new sign (Figure 3A) was created that indicates:
DANGER!
THIS MAGNET IS ALWAYS ON!
SIGN PLACEMENT
The strategic placement of signs in and around the MR environment is crucial to ensure that all individuals and patients see them before entering this area. In general, the new sign shown in Figure 1 should optimally be placed on the door or entrance to the MR system. The sign in Figure 2 should be placed on doors that serve as exterior entrances to the MR environment. The sign that states: DANGER! THIS MAGNET IS ALWAYS ON! should be placed near the doorframe so that it can be viewed by individuals and patients, especially if the door to the MR system room is open (Figure 3B).
*To obtain the new signs designed to help control access to the MR environment, please visit www.Magmedix.com or contact Frank G. Shellock, Ph.D., at the Institute for Magnetic Resonance Safety, Education, and Research, www.IMRSER.org.
References
- Finelli DA, Rezai AR, Ruggieri P, et al. MR-related heating of deep brain stimulation electrodes: an in vitro study of clinical imaging sequences. Am J Neuroradiol 2002;23:1795-1802.
- Rezai AR, Finelli D, Nyenhuis JA, et al. Neurostimulator for deep brain stimulation: Ex vivo evaluation of MRI-related heating at 1.5-Tesla. J Magn Res Imaging 2002;15:241-250.
- Shellock FG. MR safety update 2002: Implants and devices. J Magn Res Imaging 2002;16:485-496.
- Shellock FG. Biomedical implants and devices: assessment of magnetic field interactions with a 3.0-Tesla MR system. J Magn Res Imaging 2002;16:721-732.
- Shellock FG, Tkach JA, Ruggieri P, et al. Aneurysm clips: evaluation of magnetic field interactions using "long-bore" and "short-bore" 3.0-Tesla MR systems. Am J Neuroradiol (in press).
- Shellock FG, Tkach JA, Ruggieri PM, Masaryk TJ. Cardiac pacemakers, ICDs, and loop recorder: Evaluation of translational attraction using conventional ("long-bore") and "short-bore" 1.5- and 3.0-Tesla MR systems. J Cardio Magn Res (in press)
- Shellock FG. Reference Manual For Magnetic Resonance Safety: 2003 ed. Salt Lake City: Amirsys (www.Amirsys.com and www.Elsevier.com).
- U. S. Department Of Health and Human Services, Center for Devices and Radiological Health Food and Drug Administration, Guidance for the Submission Of Premarket Notifications for Magnetic Resonance Diagnostic Devices, Issued Nov. 14, 1998.
Figure 1. New sign (enlarged to show detail) designed to help control access to the MR environment. This sign should be placed on the door to the MR system room. A, Top part of sign.
Figure 1B. Bottom part of the new sign.
Figure 2. New sign designed to help control access to the MR environment. This sign should be placed at the entrances to the MR environment.
Figure 3A. New sign designed to help control access to the MR environment.
Figure 3B. This sign should be placed near the doorframe so that it can be viewed by individuals and patients, especially if the door to the MR system room is open.
