Designing GABA-edited magnetic resonance spectroscopy studies: Considerations of scan duration, signal-to-noise ratio and sample size

TitleDesigning GABA-edited magnetic resonance spectroscopy studies: Considerations of scan duration, signal-to-noise ratio and sample size
Publication TypeJournal Article
Year of Publication2018
AuthorsMikkelsen M, Loo RS, Puts NAJ, Edden RAE, Harris AD
JournalJ Neurosci Methods
Volume303
Pagination86-94
Date Published2018 Jun 01
ISSN1872-678X
KeywordsAdult, Cerebral Cortex, Computer Simulation, Female, gamma-Aminobutyric Acid, Humans, Magnetic Resonance Spectroscopy, Male, Neuroimaging, Research Design, Sample Size, Signal-To-Noise Ratio, Young Adult
Abstract

BACKGROUND: The relationships between scan duration, signal-to-noise ratio (SNR) and sample size must be considered and understood to design optimal GABA-edited magnetic resonance spectroscopy (MRS) studies.

NEW METHOD: Simulations investigated the effects of signal averaging on SNR, measurement error and group-level variance against a known ground truth. Relative root mean square errors (measurement error) and coefficients of variation (group-level variance) were calculated. GABA-edited data from 18 participants acquired from five voxels were used to examine the relationships between scan duration, SNR and quantitative outcomes in vivo. These relationships were then used to determine the sample sizes required to observe different effect sizes.

RESULTS: In both simulated and in vivo data, SNR increased with the square root of the number of averages. Both measurement error and group-level variance were shown to follow an inverse-square-root function, indicating no significant impact of cumulative artifacts. Comparisons between the first two-thirds of the data and the full dataset showed no statistical difference in group-level variance. There was, however, some variability across the five voxels depending on SNR, which impacted the sample sizes needed to detect group differences in specific brain regions.

COMPARISON WITH EXISTING METHODS: Typical scan durations can be reduced if taking into account a statistically acceptable amount of variance and the magnitudes of predicted effects.

CONCLUSIONS: While scan duration in GABA-edited MRS has typically been considered in terms of SNR, it is more appropriate to think in terms of the amount of measurement error and group-level variance that provides sufficient statistical power.

DOI10.1016/j.jneumeth.2018.02.012
Alternate JournalJ Neurosci Methods
PubMed ID29476871
PubMed Central IDPMC5940501
Grant ListU54 HD079123 / HD / NICHD NIH HHS / United States
R21 NS077300 / NS / NINDS NIH HHS / United States
K99 MH107719 / MH / NIMH NIH HHS / United States
R00 MH107719 / MH / NIMH NIH HHS / United States
R01 EB016089 / EB / NIBIB NIH HHS / United States
K08 NS063956 / NS / NINDS NIH HHS / United States
P41 EB015909 / EB / NIBIB NIH HHS / United States