Performance Concerns
Electromagnetic Interference (EMI)

Medical imaging systems can be sensitive to electromagnetic interference (EMI). EMI may be caused by electrical equipment, motors, moving metal objects such as cars, trucks and elevators, and by transportation systems that run on electrical power such as subways and trains. Proper site layout based upon an awareness of the impact this existing equipment may have on the medical imaging system can avoid many of these issues. For example, avoiding the placement of EMI sensitive imaging equipment near electrical rooms, large transformers and motors, parking garages, roadways, and elevators can aid in the prevention of potential EMI issues (as well as the significant vibrations associated with many of these elements).
Unfortunately, EMI issues cannot always be avoided especially in large urban areas where an owner may have limited placement options. This does not mean that imaging equipment cannot be installed in an EMI environment that exceeds manufacturer specifications. In fact, there are solutions to EMI issues. EMI shielding consultants are available that can survey existing buildings to quantify the EMI environment to determine if a facility meets the equipment EMI criteria. If the building is under construction, a consultant can approximate the source(s) of EMI based upon the electrical layouts and the proximity of EMI sensitive equipment to items such as moving metal found in elevators or subways or electrical sources. Ideally, addressing performance considerations prior to or during the construction period results in the most cost effective solution for optimal performance of the medical imaging equipment.

EMI issues also may be endemic to the facility itself in the case of a retrofit of an MRI suite. MRI scanners can permanently magnetize steel and other ferromagnetic components within the building structure, and the resulting magnetic field can cause EMI within the room after the MRI system is removed. Steel shielding from the old MRI system, steel beams, and corrugated metal deck and rebar inside concrete floors and ceilings are common culprits when this type of interference exists.

In the event that a site does not or will not meet the manufacturer's requirements for EMI, a shielding consultant could propose shielding options that will reduce the EMI in the area around EMI sensitive equipment. These solutions typically come in two forms; passive shielding and active shielding.

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