Progress in MRI magnets

Since its appearance in the early 1980's, Magnetic Resonance Imaging (MRI) has taken its place as a major player in the noninvasive diagnosis of disea se. It is the imaging modality of choice for detecting abnormalities of the brain, spine and musculoskeletal systems. it is on the verge of widespread application in diagnosis of cardiovascular disease and in image guided sur gery. While permanent and resistive magnets are used for low field applicat ions ("open" MRI) most systems use high field superconducting magnets makin g MRI the largest commercial application of superconductivity. The MRI magnet is the largest and most expensive component in the MRI syste m Magnet configuration is the determining factor in MRI system architecture and directly connected to issues such as patient comfort, ease of siting, life cycle cost and functionality. All of these factors drive magnet requir ements. Thus, MRI magnet requirements are determined by a combination of MRI system needs, technical requirements and market forces, plus the need for continu ous reduction of both magnet-acquisition cost and total cost of ownership. Cost of ownership, in turn, includes siting installation, operation and ser vice. In this paper we trace the evolution of superconducting MRT magnet systems - taking note of the importance of advances in cryogenic technology and des ign practice - as they have responded to both market forces and competing m agnet technologies.