This report originally appeared in the January 2009 issue of DOTmed Business News.

When Ken Poteete was the CEO for Georgetown Healthcare System, the health care provider upgraded from a .5T to a 1.5T. Even though the equipment was upgraded, there were still problems. "When the install was complete, some of the protocols produced poor image quality," says Poteete. "After two weeks of troubleshooting, it turned out there was a breach in the RF shield."

There are many questions that need to be answered and decisions to be made when it's time to design a shield. All MRI's need RF shielding but the need for magnetic shielding is a function of magnet location with respect to uncontrolled or public areas. The decision to include magnetic shielding is one of the most important, especially when it comes to cost. The use of annealed steel plate or silicon steel, in a very specific geometry, is required to capture and contain the magnetic field.
"There's often confusion in shielding among general contractors. I have to explain that there is a difference between RF shielding and magnetic shielding," says Mike Profeta, President of Magnetic Resonance Technologies Inc. "RF shielding prevents exterior radio frequencies from getting to the MRI system in order to keep interference or artifacts out of the images. Magnetic shielding is required most frequently when the system's 5 gauss magnetic field extends into uncontrolled areas and needs to be captured."

Joseph Thompson, owner of Assured Imaging Services, says, "Interference of various kinds of waves can lead to distorted images, so every MRI suite should have proper shielding to produce quality images."

For those using the low powered Tesla magnets, there's no need to worry about what's ahead.

"Many customers are getting 1.5T or an open magnet, and looking ahead to what needs to be changed when they upgrade to a 3T, but quite often there really isn't anything else they need to do," says Ben Turner, Vice President of Sales and Marketing, ETS-Lindgren. "Most shields that are suitable for 1.5 are also suitable for 3T. That's something the end user needs to be aware of. They could be hit with an additional cost when nothing is really being added."

Material Choices

A number of materials are utilized for MRI shielding as companies make use of aluminum, galvanized steel and conductive copper to isolate the system from disturbances. Each company has its own spin on what's best for a room.

According to Marc Holder, Operations Manager of Global Partners in Shielding, Inc, you can basically use any conductive material to do RF shielding and each has its own merits.

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