Present status of MRI magnets at Oxford

The advent of magnetic resonance imaging for medical diagnoses has produced the first commercial requirement for large bore superconducting magnets of high-field uniformity and reliability. Oxford Superconducting Technology and Oxford Magnet Technology have succeeded in producing magnets in large quantities, meeting these requirements. As of March 1984, over 200 magnets for MRI have been produced; 150 from 0.3-0.6T and 50 between 1.0-2.0T. For the medium-field range of magnets, field uniformities of 25ppm over a 0.5m diameter sphere and 5ppm over a 0.3m diameter sphere have been consistantly demonstrated. For the high-field range, uniformities of better than 50ppm and 10ppm for the above volumes and 0.1ppm on a 0.1m diameter sphere have been demonstrated. Field stability of better than 0.1ppm per hour is consistantly obtained. The cryogen consumption of the cryostat is less than 0.5 helium liters and 1.0 nitrogen liters per hour. The purpose of this paper is to familiarize the community with the status of this growing application.