"There are two principle properties that one considers when choosing what type of metal to use for a magnetic shield, permeability and saturation," Turner says. "Permeability is the ability of the metal to attract magnetic field to it. Saturation is the ability of the metal to absorb magnetic field within its wall."

Shielding vendors also understand that MRI equipment has to be shielded from any local environment interference, such as computers, other medical equipment and appliances which may emit radio frequency signals disturbing MRI measurement. The local environment has to be shielded from RF and magnetic interference, as strong magnetic fields can mechanically damage sensitive instruments, discharge batteries, or erase magnetic media.


In this respect, the role of the shielding vendor has evolved into more of a problem solver.

"One other thing that comes into play in higher field magnets is the impact the magnets have on the environment," says Michael Krachon, Director of US Division and GM of IMEDCO. "The shielding guys provide some solutions or methods of preventing this device from affecting the rest of the building."

Money Matters

When it comes to the cost of installing a shield, there are many variables that need to be considered. What is the size of the room? What material will you be using? Do you need magnetic shielding? Is there a union requirement for a union? Is there some state regulatory body (like ACA in Florida) that needs to be involved?

"All these factors can add significant amounts of money and time," Turner says. "You can see an RF shield as low as $26,000 for shielding extremity magnets where the room is small. Or you can see a shield approach $500,000 for operative suites, where it's a couple of rooms connected with tons of RF filters and things of that nature."


Current State of the Business

Despite what's happening with today's economy, the shielding industry remains strong. Although many companies reported a drop in activity during the summer months, most are reporting overall year-to-year increases for 2008 as thousands of new shields are expected to be installed.

"There was a lull during the election process, but people are starting to make decisions again," says Vojak. "I'm very busy with more activity than I had last year."

Krachon says since the OEMs are still pushing new MRI technology and encouraging end users to upgrade to the latest and greatest, business is booming.

"Whatever they end up promoting, when they are successful, they need arrangements for a shield so for us, opportunities are out there," he says. "I don't sense any downturn. People are looking carefully, but I would represent that our business has been quite steady."

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