title: Magnetic field homogenization of the human prefrontal cortex with a set of localized electrical coils.
abstract: The prefrontal cortex is a common target brain structure in psychiatry and neuroscience due to its role in working memory and cognitive control. Large differences in magnetic susceptibility between the air-filled sinuses and the tissue/bone in the frontal part of the human head cause a strong and highly localized magnetic field focus in the prefrontal cortex. As a result, image distortion and signal dropout are observed in MR imaging. A set of external electrical coils is presented that provides localized and high-amplitude shim fields in the prefrontal cortex, with minimum impact on the rest of the brain when combined with regular zero- to second-order spherical harmonics shimming. The experimental realization of the new shim method strongly minimized or even eliminated signal dropout in gradient-echo images acquired at settings typically used in functional magnetic resonance at 4 T.
authors.affiliation: Yale University School of Medicine, Department of Diagnostic Radiology, Magnetic Resonance Research Center, New Haven, Connecticut 06520, USA. christoph.juchem@yale.edu
authors.forename: Christoph
authors.initials: C
authors.lastname: Juchem
authors.forename: Terence W
authors.initials: TW
authors.lastname: Nixon
authors.forename: Scott
authors.initials: S
authors.lastname: McIntyre
authors.forename: Douglas L
authors.initials: DL
authors.lastname: Rothman
authors.forename: Robin A
authors.initials: RA
authors.lastname: de Graaf
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D017397:Prefrontal Cortex / Q000033:anatomy & histology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers