Dynamic shim updating on the human brain.
Dynamic alteration of shim settings during a multi-slice imaging experiment can improve static magnetic-field homogeneity over extended volumes. In this report, a pre-emphasized dynamic shim updating (DSU) system capable of rapidly updating all non-degenerate zeroth through second-order shims is presented and applied to high-field multi-slice imaging studies on the human brain. DSU is utilized in both non-oblique and oblique slicing geometries while updating in-plane and through-slice shims. Image-based magnetic-field maps are used to quantify homogeneity improvements and comparisons are made on a slice-specific basis between static global shimming and increasing orders of shim inclusion utilized DSU. The influence of oblique slicing geometry on DSU-utilized global homogeneity is also quantified computationally. Finally, the effect of DSU on susceptibility artifact reduction in single-shot axial-sliced EPI is analyzed using experimental acquisitions.
Magnetic Resonance Research Center, Yale University, New Haven, CT, USA. kevin.koch@yale.edu
Kevin M
KM
Koch
Scott
S
McIntyre
Terence W
TW
Nixon
Douglas L
DL
Rothman
Robin A
RA
de Graaf
D016477:Artifacts; D001931:Brain Mapping / Q000379:methods*; D005240:Feasibility Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*