Effects of Poor Junctions on the Effectiveness of Electromagnetic Shields of MRI Rooms

Abstract

Nuclear magnetic resonance is a technique that produces high resolution volumetric images of the body without using ionizing radiation. The quality of images is significantly affected by electromagnetic fields in the environment, especially radio frequency signals and magnetic fields of 50/60 Hz, which results in the need for shielding of the room where the magnetic resonance imaging (MRI) equipment is installed. This study was undertaken to quantify the effects of poor shielding connections on image quality of MRI equipment. We compared the influence of poor connections on shielding effectiveness (SE) for magnetic fields of alternating currents in MRI cabinets with either ferromagnetic shielding (Fe-Si alloy non-oriented grain – NGO) or conductive shielding (Al). A computer simulation was compared to experimental measurements that used a metallic box with a volume of 1 m3 and gaps of 0.5 mm in the sheet’s connections. The SE of the Al shield was influenced more by the presence of gaps than the Fe-Si NGO shield.