Single-shot interleaved z-shim EPI with optimized compensation for signal losses due to susceptibility-induced field inhomogeneity at 3 T.
A new single-shot echo-planar imaging (EPI) sequence with interleaved z-shim and optimized compensation for susceptibility-induced signal loss is proposed in this paper. Experiments on human brain demonstrated that the new method is able to regain signal dropout in brain areas with severe susceptibility-induced local gradients, while its image acquisition speed is comparable to that of conventional single-shot EPI techniques. Significant signal-to-noise ratio improvements were demonstrated in the ventral prefrontal and lateral temporal lobes with the new technique compared to a conventional EPI. Brain activation experiments with a bilateral finger-tapping task were performed with intentionally introduced local gradients near the left sensorimotor cortex, by a small gadolinium (Gd)-doped bottle placed on the left side of the head. The results of the functional experiments showed that the interleaved z-shim EPI sequence effectively recovered the signal loss caused by the Gd-doped bottle and reliably detected activation signals in bilateral sensorimotor regions, while the activation signals on the left side diminished considerably in a conventional EPI technique. The new technique, with the capability of reducing susceptibility artifacts and rapid scanning speed, may be particularly useful for event-related functional MRI experiments in the base of the brain, which are of great importance in neuropsychiatric studies.
Gu
Hong
H
Functional Neuroimaging Laboratory, Department of Psychiatry, Weill Medical College of Cornell University, New York, New York 10021, USA.
Feng
Hanhua
H
Zhan
Wang
W
Xu
Su
S
Silbersweig
David A
DA
Stern
Emily
E
Yang
Yihong
Y
D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000502:physiology*; D004292:Dominance, Cerebral / Q000502:physiology; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D017397:Prefrontal Cortex / Q000502:physiology; D012680:Sensitivity and Specificity; D013003:Somatosensory Cortex / Q000502:physiology; D013702:Temporal Lobe / Q000502:physiology