Magnetic Resonance Imaging (MRI) is a technology that uses a very strong magnetic field and radio frequency waves that act on the hydrogen atoms in the body. MRI is used to image all parts of the body. At Cincinnati Children’s, it is often used to image the brain, spine, joints and heart.
To view the parts of the body, the MRI machine generates a strong magnetic field that measures the electromagnetic signals produced by protons within the hydrogen atoms in the body. The magnetic field is stronger as you move toward the MR scanner opening and weaker as you move away from the scanner. To give you an idea of how powerful the magnetic field is generated by our MR machine, it’s stronger than the magnetic cranes used in the junkyards to pick up metal debris. Once the magnet in our MR machines is energized at the time it is installed, it is never turned off. The magnet is always on.
The strength of our MR machine’s magnetic field can be a danger to our patients and staff if not controlled, secured and operated in a responsible manner. Therefore, Cincinnati Children’s uses the ACR-recommended MR Safety Zone concept. Four zones are established around the MR scanner. Access becomes more limited when moving from Zone 1 to Zone 4.
MRI Zone 1
- The magnetic field is very small (<5 Gauss) in Zone 1 and there is no restriction on access. The public is free to move about Zone 1 without screening for MR safety.
MRI Zone 2
- This is a zone where the magnet is still very small (<5 Gauss), but we restrict access because it is close to the MRI scanners.
- Patients and families must be escorted into Zone 2; they cannot go in by themselves.
MRI Zone 3
- This is the area that is one doorway from the MR scanner. There may be some detectible magnetic field.
- Because the main magnetic field is so close, only people who have been through the MR safety screening process may remain in Zone 3.
MRI Zone 4
- Safety zone 4 is the actual MR scanner room. Although the magnetic field changes based on how close you are to the scanner itself, everywhere inside the scanner room is considered within the main magnetic field.
- Access to this area is restricted to people who have been through MR safety screening and need to be in the room.
The MR Safety Zone concept is but one of the various security steps we perform at Cincinnati Children’s to keep our staff, patients and families safe.
Meredith Towbin, copy editor