Normalizing data from GABA-edited MEGA-PRESS implementations at 3 Tesla

• Published in: Magnetic resonance imaging 2017-10, Vol.42, p.8-15
• Main Authors: Harris, Ashley D., Puts, Nicolaas A.J., Wijtenburg, S. Andrea, Rowland, Laura M., Mikkelsen, Mark, Barker, Peter B., Evans, C. John, Edden, Richard A.E.
• Format: Article
• Language: English
• Subjects: Adult; Cross-platform; Editing efficiency; Female; GABA; gamma-Aminobutyric Acid - metabolism; Humans; Macromolecular co-editing; Macromolecular Substances - metabolism; Magnetic Resonance Spectroscopy - methods; Male; MEGA-PRESS; Multi-site; Phantoms, Imaging
• ISSN: 0730-725X; 1873-5894
• DOI: 10.1016/j.mri.2017.04.013

Standardization of results is an important milestone in the maturation of any truly quantitative methodology. For instance, a lack of measurement agreement across imaging platforms limits multisite studies, between-study comparisons based on the literature, and inferences based on and the generalizability of results. In GABA-edited MEGA-PRESS, two key sources of differences between implementations are: differences in editing efficiency of GABA and the degree of co-editing of macromolecules (MM). In this work, GABA editing efficiency κ and MM-co-editing μ constants are determined for three widely used MEGA-PRESS implementations (on the most common MRI platforms; GE, Philips, and Siemens) by phantom experiments. Implementation-specific κ,μ-corrections were then applied to two in vivo datasets, one consisted of 8 subject scanned on the three platforms and the other one subject scanned eight times on each platform. Manufacturer-specific κ and μ values were determined as: κGE=0.436, κSiemens=0.366 and κPhilips=0.394 and μGE=0.83, μSiemens=0.625 and μPhilips=0.75. Applying the κ,μ-correction on the Cr-referenced data decreased the coefficient of variation (CV) of the data for both in vivo data sets (multisubjects: uncorrected CV=13%, κ,μ-corrected CV=5%, single subject: uncorrected CV=23%, κ,μ-corrected CV=13%) but had no significant effect on mean GABA levels. For the water-referenced results, CV increased in the multisubject data (uncorrected CV=6.7%, κ,μ-corrected CV=14%) while it decreased in the single subject data (uncorrected CV=24%, κ,μ-corrected CV=21%) and manufacturer was a significant source of variance in the κ,μ-corrected data. Applying a correction for editing efficiency and macromolecule contamination decreases the variance between different manufacturers for creatine-referenced data, but other sources of variance remain.