+ Importance of controlling access to the MRI environment
- The MRI environment has specific safety concerns related to the static magnetic field:
- Medical devices may malfunction within the static magnetic field, placing individuals with these devices at risk for serious or fatal injury1
- Other ferromagnetic items inadvertently taken into the static magnetic field pose a projectile risk and have been known to cause fatal trauma to patients, staff and others1,2
- In addition to the static field, MRI systems use large liquid helium reserves which, if accidentally released, pose a hazard to those in the vicinity (i.e., potential for asphyxiation and cryogen burns).2
- MRI system quenches can be dangerous for individuals unaware of the associated risks and the required emergency procedures within the MRI environment
- Controlling access to the MRI environment is instrumental in:1,2
- Preventing accidents and reducing risk for serious or fatal injury
- Ensuring medical devices and MRI scanning systems are not damaged and/or rendered useless
- Mitigating system downtime and maintaining a safe and effective working environment
- A four zone facility design is used to control and restrict access to the MRI environment.2
- The facility is conceptually divided into zones that physically restrict access of health care personnel into areas of danger due to proximity to the static magnetic field:2
- Zone I – Access to general public for example reception or waiting areas
- Zone II – Access to unscreened individuals; for example, change and preparation areas
- Zone III – Physically restricted barrier and consists of areas that have immediate access to the magnet room for example the control room
- Zone IV – Physically confines the magnet room or areas where the 5 gauss fringe field extends
+ Restricting access
- Entry to zone III and beyond is authorized ONLY by level 2 personnel*.
- All individuals entering zone III are under direct supervision of level 2 MRI personnel
- Zones III and IV are locked down when not under direct supervision of level 2 personnel.
- This restriction is ensured by a physical barrier that is unlocked by key or badge pass
- Combination locks should not be used, because of the risk a combination could be disseminated to other non-MRI personnel
* Level 2 MRI personnel are defined as those with MRI safety education to ensure safety of all individuals and facility resources within the MRI environment
- Clear and explicit signage is important to reinforce the safety features of the four-zone design.1,2
- Recommended signage includes:
- Clear and permanent demarcation of the 5 Gauss line on the floor in the magnet room
- Prominent danger signs on the magnet room doors (e.g., “Danger due to the presence of a Strong Magnetic Field, Do not Enter, No Ferromagnetic Objects”)
- Prominent signage and indicators that indicate the magnet is always on (e.g., a light that is lit at all times, running on back-up power source, accompanied by a sign above or beside door stating “The magnet is Always On”)
- Signage indicating-MRI zones
- Zone III and IV require signage which indicates the zone and the restricted access level
+ General design elements
- MRI environments are designed to facilitate MRT supervision of Zone IV access from the standard working position at the console.
- This environment is difficult to supervise and increase the risk of a safety incident
- Multiple entrances to zone IV are discouraged
- MRI environments are designed to encourage quality patient care:
- MRTs are able to directly monitor and visualize patients in the magnet bore
- MRTs are able to hear patients between scans (consideration of types of material used in construction and background noise levels in control room)
- Patient confidentiality is considered by restricting line of sight of patient information on computer screens or desks.
- Shellock FG. Reference Manual for Magnetic Resonance Safety, Implants, and Devices. 2012 Ed. Los Angeles, CA: Biomedical Research Publishing Group; 2012.
- Kanal E, et al. American College of Radiology White Paper on MRI safety. AJR 2007;188:1-27.