A Knife, Spoons and a 10-Pence Coin Pierced Tissue-Like Gel After an MRI Magnet Yanked Them Into Flight

Republished by AIC Engineering. All rights belong to the original publisher; see Source below.

A knife pulled toward a hospital MRI scanner plunged 5.5 centimeters into a block of gel designed to mimic human tissue. A teaspoon went 5 centimeters deep, a fork 4 centimeters, and a spoon 3.5 centimeters. Even a British 10-pence coin broke the surface, sinking half a centimeter.

Those were the results when researchers deliberately slid common objects toward a clinical 3-tesla MRI magnet to see what it would do to them. Two empty biscuit tins did not pierce the gel, but they struck it hard enough to dent their own bases, drive the test rig deeper into the scanner and break a protective shield layer.

The experiment, led by Shao J. Ong of National University Hospital in Singapore with co-authors in Singapore and Cambridge, England, was published in The BMJ in its December 2023 Christmas issue. Its acronym was suitably festive: CHRISTMAS, for Common Healthcare Related Instruments Subjected To Magnetic Attraction Study.

A Launch Funnel, Ballistic Gel and a Measurement Called SANTA

MRI scanners use extremely strong magnetic fields, and objects containing ferromagnetic metals such as iron can be pulled toward them. The FDA warns that such objects, from keys and phones to oxygen tanks, can become projectiles that damage the scanner or injure people, and that careful screening of people and objects entering the MRI area is critical.

To measure that risk safely, the team built what it called an electromagnetic launch funnel, a rig of polystyrene foam and acrylic tubes that slid along the scanner table. At the scanner's opening sat a block of 10% gelatin ballistic gel, the type used to simulate tissue in firearms testing.

Objects were nudged forward until the magnet's pull overcame friction and they began to accelerate. The researchers recorded that tipping point as the SANTA value, short for site where applied Newtonian mechanics triggers acceleration.

Weight Did Not Predict Which Objects Were Most Dangerous

The distances varied widely. The knife and both biscuit tins began accelerating from 152 to 161 centimeters away, about 5 feet. The 1p, 2p, 5p, and 10p coins started moving from more than a meter away.

There was no apparent link between an object's weight and how far away the magnet grabbed it. That matters because heft is not a reliable guide to which items pose the greatest risk.

Not every coin behaved the same way. The 20p, 50p and £2 coins, made of non-magnetic alloys, were not attracted at all. A £1 coin began moving only 3 centimeters from the gel and then simply fell. The 1p, 2p and 5p coins, which are steel-based, stuck to the gel and dented it without breaking through.

Real Accidents Show the Stakes

Incidents involving MRI magnets are uncommon but can be deadly. In 2001, 6-year-old Michael Colombini died at Westchester Medical Center in New York after a metal oxygen tank was pulled into the scanner while he was inside, CBS News reported.

In July 2025, a 61-year-old man wearing a metal chain was pulled into an MRI machine at a facility in Westbury, on Long Island, ABC7 reported. He was not a patient; police said he was there with someone else. He died the next day, and police said the death appeared to be an accident.

The FDA says it receives around 300 adverse event reports involving MRI scanners and coils each year. Most involve heating or burns, but projectile injuries are among the problems reported. An earlier analysis of 389 FDA reports spanning a decade, cited in a 2008 Joint Commission safety alert, found that about 10% involved projectiles, Relias Media reported.

The Study's Limits and Its Practical Message

The authors acknowledge several caveats. The ballistic gel was validated mainly for high-impact wounds, not slower projectiles, and the experiment did not model clothing, skin or tissue thickness, which would likely reduce penetration. Objects were also lined up directly with the magnetic field, which probably overstates the pull compared with real-world approaches from an angle. Only one scanner was tested.

Even so, their conclusion is direct. Common healthcare items can cause serious harm if they are pulled into an MRI, and the force of the tins suggests larger objects could fracture bones. They urge staff to avoid carrying metal items such as pens and pen torches into the magnet room, call for extra vigilance and handheld metal detectors with drowsy, confused or unconscious patients, and recommend keeping holiday treats in plastic tubs or paper boxes rather than metal tins near the scanner.

They also strongly advise against anyone repeating the experiment without extensive safety measures.

For patients and visitors, the practical steps are simple. Answer MRI screening questions carefully, remove jewelry and metal items when asked, and tell staff about any metal on or in your body before entering the scanner area.

Source

• Medical Daily (2026-10-22)
• Original article: A Knife, Spoons and a 10-Pence Coin Pierced Tissue-Like Gel After an MRI Magnet Yanked Them Into Flight
• https://www.medicaldaily.com/mri-magnet-flying-objects-christmas-study-cutlery-coins-480272