Figure 1
Crosstalk concerns result in
increased magnetic shielding
requirements due to MRI systems
in close proximity.
It is also important to consider the areas surrounding imaging equipment that will need radiation and MRI shielding. There are many pieces of equipment that could be adversely impacted by high static magnetic fields similar to those generated by an MRI system. Ultrasound equipment, computerized tomography (CT), cathode ray tube (CRT) monitors, linear accelerators, and electron microscopes are just a few examples of equipment that can be negatively impacted by the one Gauss fringe field. Magnetic shielding costs can be reduced by placing
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Figure 2
Providing separation between
adjacent MRI systems will
reduce the potential for
crosstalk and decrease the
amount of magnetic shielding
required.
equipment at distances that are outside the maximum allowable static magnetic field as required by the OEM specifications. Figure 2 shows how providing separation between adjacent MRI systems will reduce the potential for crosstalk and decrease the amount of magnetic shielding required. It is possible to place equipment such as ultrasounds and CTs next to, above, or below an MRI system, but it should be understood that such a placement may change magnetic shielding requirements and increase shielding costs. However, there may be workflow reasons that make it advantageous to place a piece of equipment near an MRI.
Radio Frequency Shielding
Unlike magnetic shielding, Radio Frequency (RF) shielding is required for the majority of MRI applications and consists of a highly conductive material such as copper, aluminum, or galvanized steel surrounding the MRI system. Determining RF shielding requirements is fairly simple due to the fact that all RF shields consist of a six sided structure and the level of attenuation or shielding effectiveness is determined by the field strength of the MRI system to be installed. For example, MRI systems with field strengths of 1.5T or less require an RF shield that provides 100 dB of attenuation at 100 MHz while 3.0T MRI systems require a shielding system that provides a 100 dB of attenuation at 150 MHz. As the field strength of the MRI systems increase, the performance requirements of the RF shielding will typically increase as well.
