Gradient Pre-Emphasis Correction for First-order Concomitant Field on Head-only Asymmetric Gradient MRI System
Shengzhen Tao1, Paul T Weavers1, Joshua D Trzasko1, Yunhong Shu1, Seung-Kyun Lee2, Lou Frigo3, Scott Hinks3, and Matt A Bernstein1
1Radiology, Mayo Clinic, Rochester, MN, United States, 2GE Global Research, Niskayuna, NY, United States, 3GE Healthcare, Milwaukee, WI, United States
Based on Maxwell’s equation, the spatial
encoding gradient fields must be accompanied by spatially-varying higher-order
concomitant fields. Different from conventional gradient systems whose
concomitant fields contain second-order and higher spatial dependence, some MRI
platforms employ asymmetric gradient systems, and their concomitant fields also
include zero- and first-order terms. The first-order terms cause artifacts
including image blurring and ghosting in spiral acquisition and echo shifting
in EPI. Here, an efficient gradient pre-emphasis scheme suitable for real-time
implementation is demonstrated to simultaneously correct all the first-order
concomitant fields with a real-time implementation on gradient firmware typically
used for eddy current compensation.
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