Correcting frequency and phase offsets in MRS data using robust spectral registration.

TitleCorrecting frequency and phase offsets in MRS data using robust spectral registration.
Publication TypeJournal Article
Year of Publication2020
AuthorsMikkelsen M, Tapper S, Near J, Mostofsky SH, Puts NAJ, Edden RAE
JournalNMR Biomed
Volume33
Issue10
Paginatione4368
Date Published2020 Oct
ISSN1099-1492
Abstract

An algorithm for retrospective correction of frequency and phase offsets in MRS data is presented. The algorithm, termed robust spectral registration (rSR), contains a set of subroutines designed to robustly align individual transients in a given dataset even in cases of significant frequency and phase offsets or unstable lipid contamination and residual water signals. Data acquired by complex multiplexed editing approaches with distinct subspectral profiles are also accurately aligned. Automated removal of unstable lipid contamination and residual water signals is applied first, when needed. Frequency and phase offsets are corrected in the time domain by aligning each transient to a weighted average reference in a statistically optimal order using nonlinear least-squares optimization. The alignment of subspectra in edited datasets is performed using an approach that specifically targets subtraction artifacts in the frequency domain. Weighted averaging is then used for signal averaging to down-weight poorer-quality transients. Algorithm performance was assessed on one simulated and 67 in vivo pediatric GABA-/GSH-edited HERMES datasets and compared with the performance of a multistep correction method previously developed for aligning HERMES data. The performance of the novel approach was quantitatively assessed by comparing the estimated frequency/phase offsets against the known values for the simulated dataset or by examining the presence of subtraction artifacts in the in vivo data. Spectral quality was improved following robust alignment, especially in cases of significant spectral distortion. rSR reduced more subtraction artifacts than the multistep method in 64% of the GABA difference spectra and 75% of the GSH difference spectra. rSR overcomes the major challenges of frequency and phase correction.

DOI10.1002/nbm.4368
Alternate JournalNMR Biomed
PubMed ID32656879
Grant ListP41 EB015909 / EB / NIBIB NIH HHS / United States
R01 EB016089 / EB / NIBIB NIH HHS / United States
R01 EB023963 / EB / NIBIB NIH HHS / United States
R01 MH106564 / MH / NIMH NIH HHS / United States
R01 NS096207 / NS / NINDS NIH HHS / United States
P41 EB015909 / EB / NIBIB NIH HHS / United States
R01 EB016089 / EB / NIBIB NIH HHS / United States
R01 EB023963 / EB / NIBIB NIH HHS / United States
R01 MH106564 / MH / NIMH NIH HHS / United States
R01 NS096207 / NS / NINDS NIH HHS / United States