Physical MR safety

November 27, 2014
Joel Kellogg
From the October 2014 issue of HealthCare Business News magazine
Tobias Gilk

Magnetic resonance imaging safety can be analogized to a three-legged stool. Anything less than an equal development of three distinct domains — clinical safety, operational safety, and physical safety – makes for a very precarious position.

All the attention in the world spent checking the relative MR safety of implants, or the thermodynamic stability of a contrast agent (examples of clinical safety) does nothing to enhance either of the other domains. Similarly, subject screening protocols, appointment of an MR safety officer, or staff training regimens (examples of operational safety) are also necessary, but insufficient alone, to comprise an MR safety program. In this article, we look at the third domain, physical safety, and some of its most important constituent parts.

ACR 4-Zone – avoiding danger in the MR suite
Broadly, one of the most important elements of physical MR safety is popularly known as the 4-Zone. In a nutshell, it states that any person should be under increasing security, or have greater and greater levels of safety knowledge, as they proceed through areas with greater proximity/access to the MR equipment.

The 4-Zone concept, originally published in the earliest of the American College of Radiology’s (ACR) Guidance Documents on MR Safety, is codified in the Facilities Guidelines Institute Guidelines for Design and Construction of Healthcare Facilities hospital building code. Versions of the FGI code have been adopted by more than 20 States as their licensure standard, and the 2010 edition is the default standard for Joint Commission accredited hospitals. Even the Joint Commission’s own Diagnostic Imaging Standards, released in December of 2013 and rescinded – pending a rewrite – a few months later, contained a version of the 4-Zone concept.

Fundamentally, the 4-Zone concept is intended to keep dangerous materials and untrained persons away from the room containing the MR scanner (designated as Zone 4). It is implemented by selectively segregating persons as they arrive at the MR department, and allowing only those who must proceed towards the scanner to do so. Along the way, this person undergoes screening, both physical and clinical to make sure they aren’t bringing anything to the scanner room that could be potentially harmful, and that they don’t have any medical devices or embedded foreign material that could pose a threat to them in a powerful magnetic field.

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