"We initiated quality assurance and maintenance agreements with institutions to provide periodic testing and maintenance. The door is typically the thing that will fail first. It's a contact that is constantly being moved. But that's not all that happens. Other things happen over time, such as wood shrinking causing the seams in the compression type seals to fail, or contractors accidentally cutting a hole in the shield. Very few people address these issues until the images are bad," Profeta adds. "A good QA program includes regular shield testing and maintenance. Sometimes an MRI equipment problem can look like an RF shield problem so another real benefit to keeping shield performance and verification up to date is that it keeps the MRI service technicians working on equipment problems when they know the shield is performing properly."

Turner is amazed that some customers test the shields when the magnet is delivered but never test again until they decide to pull out the old magnet and put in a new one.


"A service or maintenance program needs to be put in place for these MR systems, maybe generated or driven by ACR, because the rooms can degrade over time and degrade in such a way that the hospitals may not recognize it and may get faulty images," Turner says. "The MRI people have specs for a reason. Something has to be done."


Upgrade Possibilities

Although upgrading your MRI system will probably not require any update of the shielding, it's still important to test the shield and fix any problems during the upgrading process. Since you are already going through the trouble of bringing in new equipment, it's usually a good time to evaluate other components of the shielded room and upgrade if needed.

"Sometimes a facility will decide to do an upgrade and then contact us to perform a qualification test, an RF test, to see what the integrity of the shielding is before we start any work," Campedelli says. "That gives us a baseline to see if the existing shielding can meet the new magnet's RF attenuation specifications."

Often, a shield will disintegrate over time in some areas. Those spots can be identified when the shield is opened up so when the old magnet is coming out before the new magnet comes in. In many cases, repairs are done at that time.

"Some of the things that are commonly done are the replacement of the door to the scan room, because a client will want one with a newer design and one that gives better shielding capabilities than the existing door," Campedelli says. "Other times, they will work in the area where the manufacturer's penetration filters come into the room because that's one of the weak spots in the shielding so they will upgrade or add electric filters."

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