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Watch Metal Objects Fly in MRI

February 21, 2024

Written by Vivian Lei

Spoon Feed
While this humorous BMJ article has some excellent tongue-in-cheek acronyms, it also demonstrates some real dangers of bringing ferromagnetic objects into the MRI environment. Don’t miss the online video of these objects hurtling toward the magnet! See below.

The researchers investigated the potential for projectile injury when common metallic objects found in a healthcare environment were brought close to a 3 T magnet using a test rig, called an ELF (electromagnetic launch funnel). The point at which the magnetic field overcomes the static friction of an object at rest was called the SANTA (site where applied newtonian mechanics triggers acceleration) value, and this was measured for common objects, such as mobile phones, pens, stethoscope, coins, cutlery, and a biscuit tin. A ballistic gel was used to simulate human tissue and placed at the entrance of the scanner bore.

Figure 3 from the article maps out the measured SANTA values and provides a more detailed list of the tested objects. The weight of the objects did not appear to correlate with their minimum safe distance (i.e. the SANTA measurement).

From cited article

Items that demonstrated potential for tissue penetration were the knife, teaspoon, fork, spoon, and 10 pence coin. The empty biscuit tins demonstrated high acceleration and force of impact, causing deformation of the tin and displacement of the ELF. The authors posit that such forces could potentially cause blunt impact injuries significant enough to break bones.

How will this change my practice?
This study reinforces the importance of multiple safety checkpoints to ensure patients and staff do not carry metallic objects near an MRI scanner. For clinicians who may be called emergently to a crashing patient in MRI, remember to check your pockets and take the stethoscope off from around your neck.

Another Spoonful
BMJ provided an excellent video and visual infographic online. Don’t miss watching these objects whiz toward the magnet with astonishing speed!

Common Healthcare Related Instruments Subjected To Magnetic Attraction Study (CHRISTMAS): prospective in situ experimental study. BMJ. 2023 Dec 21;383:e077164. doi: 10.1136/bmj-2023-077164.