Radiofrequency shielding

Radiofrequency or RF shielding is a technique for creating electromagnetic (EM) isolation, which is critical during the acquisition of MR images. RF shielding serves to both prevent external EM interference from contaminating the target tissue signal, and to ensure that signals generated by MR imaging do not escape the room.

MRI systems utilize minute changes in local EM fields in order to distinguish differences in target tissue composition. Even small disturbances may result in a number of different artifacts during image creation. Given the ubiquity of EM waves in the external environment, it is crucial that the sensitive detector elements are shielded from interference to avoid image artifact .

In actual implementation, RF shields are based on the principle of the Faraday cage, which is typically incorporated in the construction of the scanning room. While any electrically-conducting material can be used as shielding, galvanised steel and copper have been shown to be effective at a reasonable cost .