This article is from in the January 2008 issue of DOTmed Business News. A list of registered users that provide sales & service can be found at the end.

You are already familiar with the care taken to protect patients during MRI studies, such as getting written documentation of their suitability for the exam. (Did you ever work with metals? Do you have cochlear implants?) Your facility no doubt has measures to ensure that no ferrous or magnetic metals enter the MRI suite. But these protocols are just the final step in a thoughtful process to protect patients and the magnet itself. Well before the magnet is placed into service (or an MRI machine is replaced), the site and suite must be completely shielded by specialized contractors.

How large is the business of MRI shielding? DOTmed experts estimate that around 600 to 700 MRI shields are installed each year in the U.S. However that number may be shrinking while the industry is getting more competitive, according to Mark Holder, Operations Manager, Global Partners in Shielding, Inc., Passaic, NJ. "The small guys are dropping out and only the serious shielding companies are left," he says.




While most shielding projects are done from the ground up for new magnet installations, the upgrade segment is growing faster. Up to 20 percent of MRIs are installed into existing suites that must be modified for equipment upgrades. Some insurers are choosing not to cover the lower-field open MRIs anymore, further driving the upgrade market.

"We haven't seen market saturation as far as new magnets but it's coming. The upgrade business is going to be going on forever," Holder predicts.

The cost of MRI shielding runs anywhere from about $25,000 up to $1 million for a super high-field research magnet which can top 7 tesla on the measurement scale of magnetic inductivity. Most MRIs in clinical settings are in the range of 0.2 to 3 tesla.

A Field of Service Providers

MRI shielding has multiple purposes: to prevent electromagnetic fields from escaping the MRI suite, to prevent radiofrequency (RF) waves from infiltrating into the room (radio stations, planes, wireless networks), and to guard against noise from nearby sources of electrical current. All of these forces cause problems. A (5 gauss) magnetic field leach can cause harm to patients with pacemakers. Other sensitive equipment may also be impaired by subtle magnetic forces. RF and electrical interference can distort MR image quality. Many contractors offer solutions to these challenges through the use of various materials and approaches to fit the specifics of your MRI technology and your facility.




"What we are doing [in MRI shielding] is making a continuous, seamless, six-sided box out of metals," explains Mike Profeta, Magnetic Resource Technologies, Willoughby, OH. "Primarily [silicon] steel shields are set up to contain the magnetic field....You can take any metal to create the RF shield." Profeta recommends a soldered copper room. However, some companies use aluminum or galvanized steel panels for RF protection.

The OEM that manufactured the MRI provides performance specifications for the room in terms of allowable measurements for RF or magnetic readings. However, it's often left to the contractors, such as independent service companies that specialize in MRI shielding to determine the best materials and design approach.
"We use copper, galvanized and welded steel in our rooms. Each material has a different application determined by the system and the existing site," says Gregory Vojak, Medesign, Solon, OH. "We feel a copper soldered room is best for RF attenuation, although some low- and mid-field systems can benefit from the use of galvanized steel to control any outside EMI and magnetic fields that may be present. With high-field systems and 3T units, a steel shield of one quarter inch or more is recommended to help control the field produced by the magnet."
ETS-Lindgren offers all three types of RF shielding: copper, galvanized steel, or aluminum, depending on the needs of hospitals and imaging centers.

"If the need is only for RF shielding, most of the RF copper, galvanized steel and aluminum are fairly lightweight with galvanized being the heaviest of the three," says Ben Turner, Vice President of Sales and Marketing, ETS-Lindgren, whose shielding division is based in Glendale Heights, IL. "When you get into magnetic shielding that is of significant weight that begins to dictate structural issues and may force the customers to look at only a ground floor or basement site." (A super high-field magnet might require hundreds of tons of shielding.)




Contractors must work out site-specific details such as weight bearing and other engineering considerations. However most agree on some basic suggestions for hospitals and imaging centers planning to install or replace an MRI.

"Check references and do not rely on the architect to select your shielding company because they don't research companies," notes Paul Yastrab, Physicians Imaging Solutions, Akron, OH. "Always insist on two shield tests: one upon completion of the room and one after the magnet is installed."

"Get the references and test the room by an impartial tester," confirms Marshall Shannon, Director, Image Technology Consulting, LLC, DeSoto, Texas. Never, I repeat never take the word of the installer that the room is tight."

"I would advise getting the shielding contractor involved in the early stage in any type of discussion. A good one will work with your architect for free to design the system," Holder adds. "Too often inexperienced architects don't understand the nuances of shielding and may give you four inches to build a shielded wall and it doesn't work.
You've got to get it down on paper from day one."

Devil in the Details

Any large metal objects in motion near your suite (trucks, subway cars, elevators) can cause a problem for your MRI in terms of magnetic forces, vibration, and/or electrical output, all concerns for the shielding design.

In addition to site specifications, trends in MRI design also affect how new equipment is shielded. The new machines are lighter, which helps installers, but also leaves the suite more susceptible to vibration to be mitigated by the shield. New, large bore equipment may also impact shielding specifications.

Older equipment may have significant magnetic shielding already in place since MRIs of yesteryear weren't self-shielded magnetically like today's machines. However, with the increased field strength in favor today, even heavy, older shielding may not be enough if it's not welded. You will likely need to replace the shielding in the room when you upgrade to a new MRI system.

Anything that penetrates the shield requires additional attention: special RF filtering for wiring, wave guide protection on pipes, and specialized honeycomb material for air vents. Windows and doors are shielded with copper screening. The MRI suite also requires shielding a pipe for helium exhaust along with a specially secured door and window.

Specialized MRI applications require similar meticulousness such as shielding interoperative MRI systems that must work nearby surgical lighting, gases, monitors, and other equipment. Mobile and temporary MRI facilities must also be protected and aluminum is often used for RF in those settings.

Finally, it's important to remember that safety considerations for the equipment, as with patients, extend long after the room is shielded.

"People talk about quality in images but there is nothing focused on the performance of the shield, it's all focused on the performance of the scanner," Profeta says. "Be sure to
put the rooms on a planned maintenance program tailored to the individual site."

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DOTmed Registered MRI Shielding Sales and Service Companies
Names in boldface are Premium Listings.

Domestic
Doug Bonfield, ETS-Lindgren, IL
Michael Krachon, IMEDECO, IN
Michael Profeta, Magnetic Resonance Technologies, OH
Gregory Vojak, Medesign, OH
Paul Yastrab, Physicians Imaging Solutions, OH
Marshall Shannon, Image Technology Consulting, LLC, TX
DOTmed Certified/100

International
Horacio Gomez, VCG Imagen SRL, Argentina
DOTmed Certified
Jan Glavimans, Glavimans Electronics BV, Netherlands

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