Journal
MAGNETIC RESONANCE IN MEDICINE
Volume 85, Issue 5, Pages 2370-2376Publisher
WILEY
DOI: 10.1002/mrm.28607
Keywords
carbon-13; eddy currents; image artifacts; magnetic resonance spectroscopy; MRI; phosphorus-31; sodium-23; X-nuclei
Funding
- National Institute of Health ResearchCambridge Biomedical Research Centre
- Cancer Research UK [RG86786/A25117]
- Addenbrooke's Charitable Trust
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The study found line-shape distortions characteristic of eddy currents for X-nuclei, not seen for H-1. Improvements in eddy current compensation for X-nuclei reduced these distortions and improved data quality for non-Cartesian imaging.
Purpose: The aim of the study was to investigate whether incorrectly compensated eddy currents are the source of persistent X-nuclear spectroscopy and imaging artifacts, as well as methods to correct this. Methods: Pulse-acquire spectra were collected for H-1 and X-nuclei (Na-23 or P-31) using the minimum TR permitted on a 3T clinical MRI system. Data were collected in 3 orientations (axial, sagittal, and coronal) with the spoiler gradient at the end of the TR applied along the slice direction for each. Modifications to system calibration files to tailor eddy current compensation for each X-nucleus were developed and applied, and data were compared with and without these corrections for: slice-selective MRS (for Na-23 and P-31), 2D spiral trajectories (for C-13), and 3D cones trajectories (for Na-23). Results: Line-shape distortions characteristic of eddy currents were demonstrated for X-nuclei, which were not seen for H-1. The severity of these correlated with the amplitude of the eddy current frequency compensation term applied by the system along the axis of the applied spoiler gradient. A proposed correction to eddy current compensation, taking account of the gyromagnetic ratio, was shown to dramatically reduce these distortions. The same correction was also shown to improve data quality of non-Cartesian imaging (2D spiral and 3D cones trajectories). Conclusion: A simple adaptation of the default compensation for eddy currents was shown to eliminate a range of artifacts detected on X-nuclear spectroscopy and imaging.
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