MRI Scans: What Are the Risks?

A 6-year-old boy died this weekend at a New York hospital after a blow to the head he received from a metal canister attracted to the powerful magnet of a magnetic resonance imaging machine or MRI.

The hospital has accepted full responsibility for the accident, which should not have happened if routine safety precautions had been taken. Dr. Emily Senay spoke with the Early Show to explain more about the accident and the risks associated with MRI technology.

How does an accident like this happen?

These accidents are very rare, but the nature of magnetic imaging means that the risk is very real.

Magnetic resonance imaging has been around for almost 25 years now and is used to diagnose a wide variety of injuries and illnesses. It uses a magnetic field to provide detailed three-dimensional images of the inside of the body.

The patient lies inside a tube surrounded by a powerful magnet that generates the images, and at the same time it generates a powerful magnetic field in the room.

That magnetic field is strong enough to attract even heavy metal objects into the tube at high speeds, which can obviously cause bodily harm if there's a patient inside, which is why there are also strict safety guidelines that govern the use of the machines.

What happened to the boy in New York?

He went in for a postsurgical MRI last Friday, and somehow a metal oxygen canister was brought into the room while the machine was on, contrary to safety rules. The canister became magnetized by the MRI's magnet and flew into the opening while the boy was inside. The canister struck him in the head, and he died 2 days later as a result of those injuries.

How common are these accidents?

They are extremely rare--out of an estimated 8 million MRIs given every year, there have only been a handful of cases like this one. There was a case where a policeman's gun was yanked from its holster and fired a shot into the wall. There was another where a woman's hairpin went up her nose and lodged in her throat.

What precautions are taken to avoid MRI injuries?

MRI personnel are trained to avoid obvious risks like an metal oxygen canister in the room, and also to take other precautions.

Patients should remove all metal objects from pockets, clothing, hair, including jewelry, watches, earrings, or any other rings. Also remove any metallic eyeliner, which can sometimes cause the eyelid to flutter, and make sure you don't forget to mention any metal implants you might have under the skin when asked by the technician.

Are all metal implants affected by an MRI?

Some are and some aren't. Dental fillings aren't the type of metal that is affected and not all implants are affected either. Most artificial joints and surgical wires and staples are not a problem because they are firmly embedded in bone or scar tissue. Some intrauterine devices are okay, but some are not, so you need to know wat kind you've got.

But there are also implants like pacemakers, defibrillators, metal clips in the brain, insulin pumps, nerve stimulators for back pain, cochlear implants in the ear, and any metal in the eye or eye socket that may be affected.

In fact, the eyes are very vulnerable to even tiny flakes of metal. If you are a metalworker or have ever worked with metal and are not sure if you might have metal shavings in or around your eye, you should get an X-ray before undergoing an MRI.

Any other risks from the magnet we should know about before we get an MRI?

The skin around a tattoo that contains metal can redden and sting.
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