Radiology - MRI Safety

All magnets have a fringe field that extends from the center of the magnet. Rooms are shielded as much as possible to contain this field but only people who have been cleared by the SCAN Center should be allowed in the controlled access areas of the center.

If a quench occurs, everyone must be removed from the room immediately. The vapors and gases are very cold and can cause frost-bite. They also often condense the moisture in air, creating a highly visible fog that can replace oxygen in the room.

MR scanners are super cooled with inert gases such as helium. A quench is the rapid boiling off of these cryogens intentionally or unintentionally.

Since there have been documented cases of tattoos burning the skin you must let them know there is a small chance of this. At that time they can back out of the study if they want. If they do feel a strange sensation during the scan have them squeeze the emergency ball as soon as possible and apply a cold compress to the area. The study is complete at this time.

The following items can NEVER be allowed into the scanning room:
cardiac pacemakers, cochlear (inner ear) implants, ferromagnetic or unidentifiable aneurysm clips of the brain, implanted neuro stimulators, metal or unidentifiable foreign bodies in the eyes, and implanted pumps to deliver medicine that cannot be removed.
If a subject works around metal and cannot say for sure they have never had any metal in their eyes the study should be canceled.

If a quench occurs, everyone must be removed from the room immediately. The vapors and gases are very cold and can cause frostbite. They also often condense the moisture in air, creating a highly visible fog that can replace oxygen in the room.

The magnetic field can seriously damage or impair the following personal items:
Cameras, watches, credit and bank cards, hearing aids, hair accessories, belt buckles, shoes and I-pods just to name a few. Please remember to empty ALL of your pockets before entering the scanning room.

The MRI scanner produces very high acoustic noise, which can reach excess of 130 DbA. Everyone who is scanned must wear both ear plugs and headset during the exam.

Shutting power to the PDU may be required for life threatening situations such as:
Fire in the computer room, fire, sparks, loud noises emanating from the scan room, flooding or sprinkling system goes off, and catastrophic equipment failure. These reasons should be life threatening. It is important to remember that pressing the emergency stop button shuts the power to the scanner to but the magnetic field is still active.

Dissipation of the absorbed RF energy is described in terms of Specific Absorption Rate (SAR), measured in watts/kg. SAR is calculated by the patient’s weight and the expected increase in body temperature for each imaging pulse sequence. The scanner will calculate how much heat the patient will be absorbed if it is too high the scan will not run.

Heat deposition and nerve stimulation are hazards of a varying magnetic field.

A 3T magnet is double the strength of a 1.5T unit. It is important to remember that objects that are clear for a 1.5T magnet cannot go into a 3T magnet. Mrisafety.com has the largest database of items that are cleared for the 3T environment.

Translation describes the force that attracts ferrous objects to the center of the magnetic field. It is sometimes referred to as the projectile effect. Rotation is the term that relates to the force of the North and South poles and the orientation of the scanner’s magnetic field. Ferrous objects will attempt to align their long axes with this orientation and will rotate until they are aligned with the magnetic field.

When a patient crosses their legs or intertwines their fingers a circuit is formed and it is more likely to cause peripheral nerve stimulation.

An intentional quench is done in an emergency to run the magnetic field to zero. This is done in extreme emergencies only (ex- a projectile that is pinning a patient against the magnet, injuring them).

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