title: Requirements for room temperature shimming of the human brain.
abstract: Room temperature (RT) shims are used routinely in MRI to remove global and local B(0) field inhomogeneity introduced by the subject. Most clinical scanners use only second-order spherical harmonic terms, but with the increasing availability of very high field systems, third- and fourth-order terms are a serious consideration. However, choosing appropriate coil strengths is of critical importance in shim coil design since overspecification of the shim strengths can lead to a variety of problems, including shim coil self-resonance. In this study B(0) field map data collected over a period of 6 months (over 400 brain volumes) were analyzed to find the characteristic B-fields required to shim these brains. These data can be used to specify the coil requirements to effectively shim the human brain.
authors.affiliation: Centre for Functional Magnetic Resonance Imaging of the Brain, University of Oxford, John Radcliffe Hospital, UK. stuart@fmrib.ox.ac.uk
authors.forename: Stuart
authors.initials: S
authors.lastname: Clare
authors.forename: John
authors.initials: J
authors.lastname: Evans
authors.forename: Peter
authors.initials: P
authors.lastname: Jezzard
mesh_terms: D001931:Brain Mapping / Q000295:instrumentation*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D013696:Temperature