NMR and MRI Medical Scanners: Surviving the "Invisible Force"

Magnetic resonance imaging (MRI) is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body. MRI and nuclear magnetic resonance (NMR) scanners are found in hospitals, nuclear medicine...


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Magnetic resonance imaging (MRI) is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body. MRI and nuclear magnetic resonance (NMR) scanners are found in hospitals, nuclear medicine clinics, radiation departments, research facilities and universities across the country. Response personnel must rely on education, signage, on-site visits and knowledgeable facility personnel to understand the hazards posed by MRI and NMR facilities during emergency responses.

In many cases, MRIs give different information about structures in the body than can be seen with an X-ray, ultrasound or computed tomography (CT) scan. MRIs also may show problems that cannot be seen with other imaging methods. NMR uses magnetic fields for research involving radiation and atoms and the identification of structures of organic compounds. While the MRI is used for medical imaging and the NMR is used for research, they have one thing in common – the “invisible force,” a powerful magnetic field that cannot be detected by the human senses.

Signs posted throughout these facilities alert emergency responders to dangerous locations. Primary hazards for responders are magnetic fields and cryogenic liquids used to cool magnets. These magnets can range from 30,000 to 60,000 times greater than the magnetic field of the earth. The fringe magnetic field extending around the scanners creates an environment where ferromagnetic objects become high-speed, potentially fatal projectiles. Metal implants, prostheses and foreign metallic bodies (even those not ferromagnetic) can move or dislodge, causing severe injury.

Firefighter equipment, including but not limited to self-contained breathing apparatus (SCBA), axes and other tools, radios, flashlights, stretchers and defibrillators and any other objects that are ferrous (iron-containing) are not safe to be used around the magnet, nor are metal belt buckles, steel-tipped shoes and any steel protection in firefighter boots. This includes portable fire extinguishers as well. Most facilities have non-ferromagnetic fire extinguishers on site.

Unusual incidents

Accidents have occurred where tools, mop buckets, floor polishers, chairs, acetylene and oxygen tanks and other equipment have been drawn into the magnets during daily operations and during maintenance and repairs. Cell phones, ID cards and credit cards may not work after exposure to a magnetic field.

In 2002, a 6-year-old boy was killed during an MRI scan when a metal oxygen tank was drawn across the room into the scanner by the magnetic force, fracturing his skull and causing brain damage. In 2003, a repairman broke his arm when a piece of metal pinned him to an MRI. He carried the metal into the room and the force of the magnet attracted the metal and the repairman carrying the metal against the MRI machine. Firefighters were called to release him from the machine and treat his injuries.

When responding to an accident where someone has been pinned by a metal object, determine whether the object pinning the victim can be removed without causing further injury. If removal is successful, immediately evacuate the victim to an area outside the magnet room and restrict entry into the magnet room by others. Resuscitation or treatment aided by ferromagnetic devices can be administered once the victim is outside the magnet room.

If a life-threatening emergency exists and there is no way to free the victim without eliminating the magnetic field, then it will be necessary to initiate a magnet “quench” to bring down the magnetic field. The quench procedure will create a dangerous environment. Expect a loud noise from the escape of cryogens and a release of a dense white fog. There is a high risk of asphyxiation and potential for frostbite. As the magnetic field decreases, the object pinning the victim may fall and could cause further damage. Do not perform this procedure unless you are prepared to immediately evacuate yourselves and the victim if oxygen is displaced from the room.

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