By Joel Kellogg, ETS-Lindgren and Dave Jordan, West Physics

Designing space for medical imaging equipment can be quite complex and involved as there are many items that must be addressed in order to successfully develop a site. Good site planning must thoroughly evaluate both the impact of the imaging equipment on the surroundings (environmental concerns) and the impact of the space itself on the performance of the imaging equipment and the personnel using the equipment (performance concerns). Depending upon the equipment, concerns may include radiation, magnetic and/or radio frequency (RF) shielding, electromagnetic interference (EMI), vibration, and acoustic requirements. There may also be concerns over co-siting medical imaging equipment as one piece of equipment could have a negative impact on another piece of equipment. As a result, it is critical to develop a site plan and workflow process well in advance that is functional for users, patients, and the planned equipment.

Environmental Concerns

Shielding (Magnetic, Radio Frequency and Radiation) and Acoustics
Magnetic Shielding

Shielding is critical to the proper development of a site for imaging equipment. Some imaging equipment will require radiation shielding and other equipment, mainly Magnetic Resonance Imaging (MRI) systems, will require Radio Frequency (RF) and magnetic shielding. Careful planning that accounts for workflow and surrounding areas can also help reduce the level of shielding required representing a cost savings to the owner while providing a functional, efficient work environment.

When planning for MRI systems, there are some simple things that can be done to avoid excessive magnetic shielding costs. While the majority of MRI systems require an RF shield, the magnetic shielding requirements are driven by specific site selection. For example, in large imaging suites with multiple MRI systems, placing MRI systems side-by-side with limited spacing between MRI suites will drive the requirements for magnetic shielding. In some cases, this may also require expensive modifications to the equipment itself. While many sites will only be concerned with meeting FDA recommendations of 5-Gauss containment in public areas surrounding MRI suites, placing MRI systems next to each other can create a concern for crosstalk. Crosstalk results in MRI systems having an interactive impact on each other. Figure 1 shows crosstalk concerns which result in increased magnetic shielding requirements. To avoid crosstalk in a situation where MRI systems are placed in close proximity, the magnetic shielding requirements may change. For example, a magnet vendor may require that the 3 Gauss fringe fields do not intersect, which means that the magnetic shielding will need to be designed to contain 3 Gauss rather than 5 Gauss. This will result in a heavier magnetic shield and increased shielding costs. A simple solution may be to place the MRI equipment rooms, which house the MRI's electronic systems, between adjacent MRI systems. This may provide enough spacing so that the 3 Gauss lines do not intersect; however, even if the 3 Gauss lines intersect, the amount of magnetic shielding required to separate the 3 Gauss lines will cost much less than having the MRI systems located side by side.

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