Magnetic field homogenization of the human prefrontal cortex with a set of localized electrical coils.
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.
Juchem
Christoph
C
Yale University School of Medicine, Department of Diagnostic Radiology, Magnetic Resonance Research Center, New Haven, Connecticut 06520, USA. christoph.juchem@yale.edu
Nixon
Terence W
TW
McIntyre
Scott
S
Rothman
Douglas L
DL
de Graaf
Robin A
RA
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