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Retrospective correction of frequency drift in spectral editing: The GABA editing example
Author(s) -
Veen Jan Willem,
Marenco Stefano,
Berman Karen F.,
Shen Jun
Publication year - 2017
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3725
Subject(s) - robustness (evolution) , computer science , voxel , offset (computer science) , low frequency , algorithm , chemistry , artificial intelligence , telecommunications , biochemistry , gene , programming language
GABA levels can be measured using proton MRS with a two‐step editing sequence. However due to the low concentration of GABA, long acquisition time is usually needed to achieve sufficient SNR to detect small differences in many psychiatric disorders. During this long scan time the frequency offset of the measured voxel can change because of magnetic field drift and patient movement. This drift will change the frequency of the editing pulse relative to that of metabolites, leading to errors in quantification. In this article we describe a retrospective method to correct for frequency drift in spectral editing. A series of reference signals for each metabolite was generated for a range of frequency offsets and then averaged together based on the history of frequency changes over the scan. These customized basis sets were used to fit the in vivo data. Our results demonstrate the effectiveness of the correction method and the remarkable robustness of a GABA editing technique with a top hat editing profile in the presence of frequency drift.

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