Characterizing and correcting gradient errors in non-cartesian imaging: Are gradient errors linear time-invariant (LTI)?

Non‐Cartesian and rapid imaging sequences are more sensitive to scanner imperfections such as gradient delays and eddy currents. These imperfections vary between scanners and over time and can be a significant impediment to successful implementation and eventual adoption of non‐Cartesian techniques...

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Veröffentlicht in:Magnetic resonance in medicine Jg. 62; H. 6; S. 1466 - 1476
Hauptverfasser: Brodsky, Ethan K., Samsonov, Alexey A., Block, Walter F.
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.12.2009
Schlagworte:
Algorithms
Computer Simulation
Eddy current
gradient calibration
gradient error
Image Enhancement - methods
Image Interpretation, Computer-Assisted - methods
Imaging, Three-Dimensional - methods
k-space trajectory
k-space trajectory deviation
Magnetic Resonance Imaging - methods
Models, Biological
Models, Statistical
non-cartesian imaging
Pattern Recognition, Automated - methods
Reproducibility of Results
Sensitivity and Specificity
Time Factors
ISSN:0740-3194, 1522-2594, 1522-2594
Online-Zugang:Volltext
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Zusammenfassung:Non‐Cartesian and rapid imaging sequences are more sensitive to scanner imperfections such as gradient delays and eddy currents. These imperfections vary between scanners and over time and can be a significant impediment to successful implementation and eventual adoption of non‐Cartesian techniques by scanner manufacturers. Differences between the k‐space trajectory desired and the trajectory actually acquired lead to misregistration and reduction in image quality. While early calibration methods required considerable scan time, more recent methods can work more quickly by making certain approximations. We examine a rapid gradient calibration procedure applied to multiecho three‐dimensional projection reconstruction (3DPR) acquisitions in which the calibration runs as part of every scan. After measuring the trajectories traversed for excitations on each of the orthogonal gradient axes, trajectories for the oblique projections actually acquired during the scan are synthesized as linear combinations of these measurements. The ability to do rapid calibration depends on the assumption that gradient errors are linear and time‐invariant (LTI). This work examines the validity of these assumptions and shows that the assumption of linearity is reasonable, but that gradient errors can vary over short time periods (due to changes in gradient coil temperature) and thus it is important to use calibration data matched to the scan data. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Bibliographie:ArticleID:MRM22100
GE Healthcare
ark:/67375/WNG-34V4FBNN-V
National Institutes of Health/National Institute of Neurological Disorders and Stroke (NIH/NINDS) - No. R01NS065034
istex:6C1FD366949E579C178B8B6B3CD322BEFB16728C
National Cancer Institute (NCI) - No. 1R01CA116380
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ISSN:0740-3194
1522-2594
1522-2594
DOI:10.1002/mrm.22100