Estimation and removal of spurious echo artifacts in single‐voxel MRS using sensitivity encoding

Berrington, Adam; Považan, Michal; Barker, Peter B.

Abstract

Purpose

In localized MRS, spurious echo artifacts commonly occur when unsuppressed signal outside the volume of interest is excited and refocused. In the spectral domain, these signals often overlap with metabolite resonances and hinder accurate quantification. Because the artifacts originate from regions separate from the target MRS voxel, this work proposes that sensitivity encoding based on receive-coil sensitivity profiles may be used to separate these signal contributions.

Methods

Numerical simulations were performed to explore the effect of sensitivity-encoded separation for unknown artifact regions. An imaging-based approach was developed to identify regions that may contribute to spurious echo artifacts, and tested for sensitivity-based unfolding of signal on six data sets from three brain regions. Spectral data reconstructed using the proposed method (“ERASE”) were compared with the standard coil combination.

Results

The method was able to fully unfold artifact signals if regions were known a priori. Mismatch between estimated and true artifact regions reduced the efficiency of removal, yet metabolite signals were unaffected. Water suppression imaging was able to identify regions of unsuppressed signal, and ERASE (from up to eight regions) led to visible removal of artifacts relative to standard reconstruction. Fitting errors across major metabolites were also lower; for example, Cramér–Rao lower bounds of myo-inositol were 13.7% versus 17.5% for ERASE versus standard reconstruction, respectively.

Conclusion

The ERASE reconstruction tool was demonstrated to reduce spurious echo artifacts in single-voxel MRS. This tool may be incorporated into standard workflows to improve spectral quality when hardware limitations or other factors result in out-of-voxel signal contamination.

Citation

Berrington, A., Považan, M., & Barker, P. B. (2021). Estimation and removal of spurious echo artifacts in single‐voxel MRS using sensitivity encoding. Magnetic Resonance in Medicine, 86(5), 2339-2352. https://doi.org/10.1002/mrm.28848

• Journal Article Type: Article
• Acceptance Date: Apr 26, 2021
• Online Publication Date: Jun 28, 2021
• Publication Date: 2021-11
• Deposit Date: May 24, 2021
• Publicly Available Date: Jun 28, 2021
• Journal: Magnetic Resonance in Medicine
• Print ISSN: 0740-3194
• Electronic ISSN: 1522-2594
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 86
• Issue: 5
• Pages: 2339-2352
• DOI: https://doi.org/10.1002/mrm.28848
• Keywords: MRS; Artifact Removal; Sensitivity Encoding
• Public URL: https://nottingham-repository.worktribe.com/output/5569868
• Publisher URL: https://onlinelibrary.wiley.com/doi/full/10.1002/mrm.28848
• Additional Information: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.