MRI facilities are designed and constructed in a manner that minimizes safety risks
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 in1,2:
- 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 environment2.
- 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 field2:
- 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
- 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 design1,2.
- 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.