Advantages in the Application of Conductive Shielding for AC Magnetic Field in MRI Exam Rooms

摘要

Due to the increasing demand for installation of Magnetic Resonance Imaging (MRI) equipment in clinics and hospitals, and the difficulty to choose the location for installation of these equipment because of their high sensitivity to 60 Hz magnetic field sources, this study was carried out to present a practical solution for shielding 60 Hz magnetic field in the hospital environment. MRI is a technique that produces 3-D (volumetric) tomographic images of high resolution without using ionizing radiations. The quality of images is greatly influenced by magnetic fields of the environment, especially of 50/60 Hz, which results in the need of shielding the space where the equipment are installed. This study proposes the use of aluminum in the construction of the MRI room shield for the many advantages presented by this material when compared to ferromagnetic materials: it is lighter, easier to handle, bend, rivet or weld, it does not rust and dispenses sturdy supports for fixing on walls, resulting in the best cost-benefits ratio in short and long terms. We performed computational simulation and experiments with shields of rectangular geometries assembled with aluminum and ferromagnetic materials. The aluminum shield has proved to be advantageous, since it presents shielding effectiveness to 60 Hz magnetic field similar to those of Fe-Si GNO under certain conditions, and radio frequencies shielding also, with lower cost in the installation and maintenance of shielding in MRI rooms.