MR Safety

The magnet is always on!

The magnet is always on.

Flying Objects

What do we mean by this? Well, the main magnet (B0) is always on. MR magnets are very strong. It will attract, with a strong force, many types of metallic objects. This can be very dangerous as they can become FLYING OBJECTS and accelerate towards the center of the magnet. Guess who is often in the center of the magnet...THE PATIENT! When uncertain, error on the side of caution and assume that a metallic object is not MRI compatible. Below are a few examples of MRI accidents. Fortunately no patients were in these magnets.

What to Think About Before I Enter a Room with an MRI Magnet?

Whenever entering the MRI room as a healthcare provider you will should frisk yourself for a moment to think about what you have on you. Look for jewelery, a watch, keys, your pager, phone, and credit cards. These could become flying objects, cause burns, or cause permanent damage to the device. In the case of credit cards, they will be erased (unfortunately without erasing your bill!). Additionally, if you have personal medical devices or if you are at risk for having shrapnel near your orbit you should undergo an MRI safety screen.

Types of objects that are often forgotten

Jewelry
Pens, paperclips
Needles
Catheters with metal tips or hubs
Patient monitoring and support equipment (EKG, IV poles, pumps, ventilation support, external orthopedic hardware)
Oxygen tanks, wheelchairs
Electronics

Metal Objects Inside Patients

Similarly, metallic objects inside a person, whether medical devices (aneurysm clip, pacemaker) or shrapnel from an accident or occupational hazard (veteran who was injured, metal worker) can be a safety hazard. First, these objects can heat up much like they would in a microwave. Have you ever put metal in the microwave accidentally (sparks!)? Second, they can move when they enter the strong magnetic field. This could cause vascular, nerve, or organ injury. This is of particular concern in the orbit where small metal fragments could be very close to the orbit, optic nerve, vessels, and extra-ocular muscles. Not all metals and not all devices cause a problem. For example, most orthopedic hardware and modern vascular clips are MRI safe. Although they are outside patients, tattoos can also become very warm with certain scans and may need to be handled specially.

Medical Devices

Mechanical and electronic devices both internal and external to the patient can create danger as mentioned due to it becoming a dangerous accelerating projectile, migrate within a person (patient or employee), or heat up. Equally dangerous can be the malfunctioning due to the magnetic field. For example, while there are a few pacemakers that are MRI conditional, many conventional pacemakers are not. In theory, they may cease to function or potentially misfire.

The table below is a good summary of what items and medical devices are typically safe and unsafe with MRI. When in doubt, check it out or call radiology to inquire.

Typically Safe

Orthopedic hardware
Surgical clips, staples, sutures (older devices must be checked!)
Intravascular stents/filters

Conditional

Describes items that are safe under specific conditions.
Some more recent pacemakers

Typically Unsafe

Conventional cardiac pacemakers
Some older aneurysm clips
Metal fragments in orbit (1 case report)
Oxygen tanks, carts, chairs, stools, IV poles, gurneys, etc.
Some cosmetics, tattoos, jewelry, hairpins, etc.
Pager, watch, wallet, ID badge, pen, keys, pocketknife, etc.

Claustrophobia

Some patients will have had or anticipate having difficulties with entering a small tube for an extended period of time. Often this can be solved with oral sedatives/anxiolytics but in rare occasions if the MR study is medically necessary general anesthesia can be administered.

Additional Resources

For checking the MRI compatibility of medical devices, MRISafety.com is a valuable reference.

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