The design and use of secondary shielding in MRI systems-experiments from 4 years of operation

Whole-body superconducting magnets are essential for MRI (magnetic resonance imaging) systems to perform spectroscopy and to get high-quality imaging. These magnets produce a large fringe field that interferes with other imaging equipment in a clinical environment. An approach to shielding magnets using primary shielding, which is comprised of a light-weight flux-return yoke near the magnet and secondary shielding in the desired direction, was developed. Primary shieldings for 0.5 T and 2 T were developed, built, and tested at the authors' company, and installed at customer sites. It was found that this approach to shielding is the most cost effective in terms of using steel and achieving good homogeneity.<
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