Subtraction artifacts and frequency (Mis‐)alignment in J‐difference GABA editing. Issue 4 (27th November 2012)

• Record Type: Journal Article
• Authors: Evans, C. John; Puts, Nicolaas A.J.; Robson, Siân E.; Boy, Frederic; McGonigle, David J.; Sumner, Petroc; Singh, Krish D.; Edden, Richard A.E.
• Is Part Of: Journal of magnetic resonance imaging. Volume 38:Issue 4(2013)
• Page Start: 970
• Page End: 975
• Publication Date: 2012-11-27
• Subjects: Magnetic resonance imaging -- Periodicals; 616
• DOI: 10.1002/jmri.23923
• Languages: English
• ISSNs: 1053-1807

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="jmri23923-sec-0001" sec-type="section"> <title>Purpose</title> <p>To compare the repeatability of γ‐aminobutyric acid (GABA) measurements using <italic>J</italic>‐difference editing, before and after spectral realignment—a technique which has previously been demonstrated to improve the quality of <italic>J</italic>‐difference GABA spectra.</p> </sec> <sec id="jmri23923-sec-0002" sec-type="section"> <title>Materials and Methods</title> <p>We performed in vivo measurements in three brain regions (occipital, sensorimotor, and dorsolateral prefrontal cortex [DLPFC]), and analyzed these using alternative alignment approaches to evaluate the impact of alignment on repeatability: "Independent alignment" (aligning each subspectrum independently) and "Pairwise alignment" (aligning each <italic>on</italic> and <italic>off</italic> subspectrum as a pair) were compared.</p> </sec> <sec id="jmri23923-sec-0003" sec-type="section"> <title>Results</title> <p>Pairwise alignment improved the group mean coefficient of variation in all regions; 0.4% in occipital, 1.1% in sensorimotor, and 1.1% in DLPFC. Independent alignment resulted in subtraction artifacts in the majority of cases, and increased the coefficient of variation in the DLPFC by 9.4%. Simulations demonstrate that the GABA quantification error in datasets with high <italic>B</italic><sub><italic>0</italic></sub> drift, is 4.5% without alignment, but <1% with optimal alignment.</p> </sec> <sec id="jmri23923-sec-0004" sec-type="section"> <title>Conclusion</title> <p>Pairwise alignment improves the repeatability of GABA spectroscopy data. However, independently aligning all <italic>on</italic> and <italic>off</italic> subspectra can lead to artifacts and worse repeatability when compared with nonaligned data. J. Magn. Reson. Imaging 2013;38:970–975. © 2012 Wiley Periodicals, Inc.</p> </sec> </abstract>