The “big three” sections of an MR scanner are well known; Magnet, Gradient system, and RF system, and probably should have a fourth: Patient comfort and user experience components. We start with a review of these components, current limitations, and directions under investigation and continue to interaction between them needed to harmonize operation.
Highlights · The “big three” sections of an MR scanner are well known; Magnet, Gradient system, and RF system, but probably should have a fourth: Patient comfort and user experience components. We start with a review of these components, current limitations, and directions under investigation.
· These components have interdependent requirements and must work in harmony. It is therefore becoming rare to design magnet, gradient and RF subsystems separately and expect the system to work well when bolted together. The interaction of the gradient coil with the magnet is an important example, on which there is little in the literature.
· In this talk, the basic ideas of matching magnet homogeneity to gradient strength requirements, and gradient strength/coil to amplifier needs will be discussed. Finally the need to match gradient linearity, RF coverage region and homogeneous magnet region to prevent detection of unencoded spins from folding into the FOV will be discussed.
· We are increasingly looking for ways to relax traditional hardware specifications to make room for “softer” constraints that effect patient comfort, workflow and system cost. For example, increased bore size has become important even though it challenges gradient and RF Tx metrics.
· Strategies which add degrees of freedom to the imaging experiment have been very successful in the clinic (e.g. parallel Rx), but they can come at the expense of workflow and patient comfort if the coils and their cabling become too cumbersome. Flexible coils, high comfort coils and cable-less coils have become an active area of work but have system design implications.
· Similarly, progress in adding parallel Tx and high order B0 shimming has made a lot of progress but complicate system workflow.
· Finally, perhaps the patient should be considered as part of the system, since the electromagnetic interactions in the body can be limiting. Although full body electromagnetic body models have long been part of checking MRI safety, their role in design of the subsystems is likely to increase.
· Target audience – MR physicists or engineers interested in system design, or who need to incorporate system considerations into sub-system design.
· Outcome/Objectives – Better appreciate and utilize the thousands of man-hours that go into MRI system design.