Ethan Brodsky1,2, Walter F. Block2,3
1Radiology, University of Wisconsin - Madison, Madison, WI, USA; 2Medical Physics, University of Wisconsin, Madison, WI, USA; 3Biomedical Engineering, University of Wisconsin, Madison, WI, USA
Non-Cartesian sequences are sensitive to gradient delays and eddy currents, imperfections that vary between scanners and over time. Uncorrected trajectory errors lead to misregistration of k-space data and reductions in image quality. We apply a per-scan rapid gradient calibration and correction to multi-echo 3DPR acquisitions. Trajectories for oblique projections are synthesized by linearly combining measurements made on the three orthogonal gradient axes. This rapid calibration depends on the assumption that gradient errors are linear (with respect to gradient amplitude) and time-invariant (within a scan). We show that the assumption of linearity is reasonable, but that gradient errors can change rapidly over time, highlighting the importance of per-scan calibration.