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Film Buff investigates the facts behind outlandish movie plots.

Death by magnetised flying screwdriver: the facts.

THIS MONTH HAPPY DEATH DAY 2U

Q In HDD2U, an assailant is killed in an MRI room when the magnetic switch is flipped on and a screwdriver becomes a lethal projectile. Medical science or quack?

A DR. DANIEL SCOFFINGS MBBS. MRCP. FRCR., CONSULTANT NEURORADIOLOGIST, ADDENBROOKE’S HOSPITAL, CAMBRIDGE

MRI scanners contain a superconducting magnet that is over 100 times stronger than a fridge magnet and over 10,000 times stronger than the Earth’s magnetic field. This is achieved by lowering the temperature inside the magnet to just a few degrees above absolute zero, using liquid helium. The magnet inside the scanner is always on, as it requires a large amount of liquid helium to keep the scanner cool enough to generate the massive magnetic field needed for MRI scanning, and ‘ramping up’ the machine to this this field strength takes two to three days; it cannot happen at the press of a button.

There is a big red button inside the room of every MRI scanner, but it is only for use in an emergency to ‘quench’ the magnet, allowing the liquid helium to boil off if the magnetic field needs to be rapidly decreased. The magnetic field in the MRI scanning room is strong enough to pull metallic objects into the scanner as a projectile.

Over the years, metallic objects that have been pulled into MRI scanners include a vacuum cleaner, a wheelchair, mop buckets, a toolbox and even an off-duty policeman’s gun – which discharged a round into the scanner. There has been an instance of a patient inside the scanner being hit by a metallic oxygen cylinder and killed. It is entirely possible that a screwdriver could be pulled towards the scanner with sufficient force to penetrate somebody, but not at the press of a button. VERDICT PARTIALLY BOLLOCKS Want us to investigate if a movie scenario is bollocks? Ask us at totalfilm@futurenet.com