Review on high-temperature superconducting magnet technology for its development in ultra-high-field MRI

Abstract MR researchers pursue higher and higher B 0 fields for new discoveries in medical sciences. High-temperature superconducting (HTS) magnets exhibit potential advantages of compactness, cryogen-free operation and ultra-high field (UHF) performance when utilized as the key component in UHF-MRI systems. Intensive research on HTS magnets have been conducted in recent years. This review reports on up-to-date HTS magnet techniques, analyzing their challenges and solutions for potential application in UHF-MRI magnets. Two commercial HTS tapes of Bi2223 and REBCO are discussed, highlighting their applications in MRI/NMR magnets and other UHF magnets. Technical problems, especially for the REBCO magnet with the screening current effect, small radial tensile strength, tape performance uncertainty, etc are introduced alongside mitigation strategies. The no-insulation technique and its implications for quench transient behavior are also explored. Given the absence of an UHF-MRI magnet with the HTS technology in the world at the time of formulating this review, the achievements of some other large-scale UHF-magnet projects with the HTS technology are investigated. Sequential engineering phases with two prototype magnets are thus proposed for a developing roadmap of the HTS UHF-MRI magnet. The detailed development cost is estimated within a decent price range. Besides, for the development of a first-in-kind UHF-MRI system with an HTS magnet, the insight is provided that the UHF-magnet development is a make-or-break component and due a primary and independent project to ensure its successful integration to the entire UHF-MRI system. Beyond the introduction and the conclusion, this review is structured with eight thematic sections. The beginning of each section/sub-section is tailored to the UHF-MR researchers with an introduction to basic magnet knowledge, and the remaining and major part is presented with in-depth technical analyses for the UHF-magnet specialists.