MRI faraday cage performance during the lifetime of clinical MRI systems

This work investigated the performance of MRI Faraday cages (FCs) over the lifetime of clinical MRI systems, aiming to better inform an option to repurpose an existing FC when an MRI scanner is replaced.

FC performance was measured at acceptance testing for 40 MRI systems and for a further 11 MRI systems of various ages. Results were compared with the MRI vendor's FC specification and with measurements made when the FCs were initially built.

The majority of FCs, 63% (n = 25), had at least one measurement below specification at acceptance testing. However, no RF artefacts were observed on MR images. There were significant negative relationships between FC performance and age at the locations of the door and window (p < 0.001).

FC performance can degrade between the time of FC manufacture and initial clinical MRI scanning. However, FC attenuation levels may need to be considerably less than specification values before external RF artefacts start appearing on MR images in practice. Further degradation of FC performance may occur over time, but this may be better addressed by maintenance on the MR exam room door rather than a much more costly and time-consuming replacement of the FC.