  Purpose: To develop an efficient navigator-based motion and temporal B0 shift
correction technique for 3D multi-echo gradient-echo (ME-GRE) MRI for
quantitative susceptibility mapping (QSM) and R2* mapping. Theory and Methods:
A dual-echo 3D spiral navigator was designed to interleave with the Cartesian
ME-GRE acquisitions, allowing the acquisition of both low- and high-echo time
signals. We additionally designed a novel conjugate-phase based reconstruction
method for the joint correction of motion and temporal B0 shifts. We performed
both numerical simulation and in vivo human scans to assess the performance of
the methods. Results: Numerical simulation and human brain scans demonstrated
that the proposed technique successfully corrected artifacts induced by both
head motions and temporal B0 changes. Efficient B0-change correction with
conjugate-phase reconstruction can be performed on less than 10 clustered
k-space segments. In vivo scans showed that combining temporal B0 correction
with motion correction further reduced artifacts and improved image quality in
both R2* and QSM images. Conclusion: Our proposed approach of using 3D spiral
navigators and a novel conjugate-phase reconstruction method can improve
susceptibility-related measurements using MR.
