Reducing susceptibility artifacts in fMRI using volume-selective z-shim compensation.
Susceptibility-induced magnetic field gradients (SFGs) can result in severe signal loss in the orbitofrontal cortex (OFC) in gradient-echo-based functional MRI (fMRI) studies. Although conventional z-shim techniques can effectively recover the MRI signal in this region, the substantial penalty in imaging time hampers their use in routine fMRI studies. A modified z-shim technique with high imaging efficiency is presented in this study. In this technique, z-shim compensations are applied only to a selective volume where the susceptibility artifact is severe. The results of an fMRI study (N=6) demonstrate the feasibility of detecting the OFC activation with z-shim in whole-brain fMRI studies at a temporal resolution of 2 s.
Du
Yiping P
YP
Department of Psychiatry, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado 80010-7155, USA. Yiping.Du@UCHSC.edu
Dalwani
Manish
M
Wylie
Korey
K
Claus
Eric
E
Tregellas
Jason R
JR
D000328:Adult; D016477:Artifacts; D005240:Feasibility Studies; D005260:Female; D005625:Frontal Lobe / Q000033:anatomy & histology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged