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Magnetic Resonance Imaging relies upon the excitation and detection of resonances at radio frequencies of atomic nuclei within the cells of the human body. For optimum image quality this is performed in a very strong magnetic field which must be maintained to a very stable value -throughout the scanning period. Any object with carrying an electric current create magnetic fields. Depending on the source of the field, a magnetic field’s strength and direction can be static (direct current, DC) or alternating (alternating current, AC).

DC magnetic fields are produced by the:

• Earth total magnetic field as a background DC field
• DC current flow in moving metals, vehicles, subways, trains, and elevators
• Powerful magnets associated with MRI and NMR units
• Structural and reinforcing steel which may have been magnetized by presence of permanent magnets inside the building or exposed to strong DC currents during the construction, such as by grounding the welding equipment to structural steel during the construction

AC magnetic fields, commonly occuring at extremely low frequency (ELF) or power frequency (60 HZ) are contributed to the following sources:

• Elevated AC magnetic fields are present near electrical equipment rooms, utility station and transformer vaults, distribution bus and wire ducts.
• Transmission and distribution lines passing near the exterior of a building
• Wiring errors such as improper ground to neutral connections, in a building’s AC power system, can cause substantial ELF magnetic field conditions to exist in large areas of the building.

Vibetech Consultants provide Electromagnetic Interference (EMI) testing using state-of-the-art instrumentation and techniques. EMI test results are used to determine whether EMI levels are acceptable for installation of different types of MRI systems.

Vibetech Consultants staff has successfully completed more than 100 EMI testing projects in the United States.