Future MR Magnets - Beyond NbTi
Mark D Bird1

1National High Magnetic FIeld Lab, Florida State University, Tallahassee, FL, United States

Synopsis

An overview of the challenges associated with development of higher field human MRI magnets is presented.

Highlights

Today’s ultra-high field human MRI magnets are not uniquely large, high-field magnets. Larger, higher-field magnets are built for condensed-matter physics and magnetically-confined fusion.

The magnetic field available for human MRI is not presently limited by magnet technology, but by regulatory and financial constraints. Put differently, if you can get permission to put a person inside it, and can afford to pay for it, then the magnet can probably be built. (There might be limitations on gradient coils or rf coils, but not the dc magnet.)

Almost all human MRI magnets employ NbTi as the superconducting material. This material stops superconducting at ~12 T. High-field NMR magnets reach as much as 23.5 T with ppb uniformity over a few centimeters by using Nb3Sn superconductor. Both NbTi and Nb3Sn are Low-Temperature Superconductors (LTS).

In 1986 the first High-Temperature Superconductors (HTS) were discovered. Some of the HTS materials will superconduct at > 100 T and might be employed in future UHF MRI.

Problem Summary

There are advantages in performing MRI at higher fields [1]. It seems to be widely believed in the MRI scientific community that the magnet technology does not exist to build human MRI magnets that operate at higher fields than are presently available. While 7 T in a 90-cm room-temperature magnet-bore is considered ultra-high field for MRI, magnets providing 14 T in a 60-cm bore [2] and 11.3 T in a 100-cm bore [3, 4] have been built, although without the high uniformity and stability required for MRI. Human MRI magnets in the range of 14 T to 20 T should be possible.

Acknowledgements

No acknowledgement found.

References

No reference found.
Proc. Intl. Soc. Mag. Reson. Med. 25 (2017)