Long-term reproducibility of GABA magnetic resonance spectroscopy

Near, Jamie; Ho, Yi-Ching Lynn; Sandberg, Kristian; Kumaragamage, Chathura; Blicher, Jakob Udby

doi:10.1016/j.neuroimage.2014.05.059

Cited by 65 publications

(88 citation statements)

References 29 publications

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“…Repeatability studies that measure GABA over time44, 45, 46, 47 report lower fluctuations in GABA per participant with a CV of 4‐12% (mean CV, for GABA plus macromolecules referenced to either water or creatine at 3 T). However, these studies use a MEGA‐PRESS sequence, without macromolecular suppression.…”

Section: Discussionmentioning

confidence: 99%

Maximizing sensitivity for fast GABA edited spectroscopy in the visual cortex at 7 T

et al. 2018

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The combination of functional MRI (fMRI) and MRS is a promising approach to relate BOLD imaging to neuronal metabolism, especially at high field strength. However, typical scan times for GABA edited spectroscopy are of the order of 6‐30 min, which is long compared with functional changes observed with fMRI.The aim of this study is to reduce scan time and increase GABA sensitivity for edited spectroscopy in the human visual cortex, by enlarging the volume of activated tissue in the primary visual cortex. A dedicated setup at 7 T for combined fMRI and GABA MRS is developed. This setup consists of a half volume multi‐transmit coil with a large screen for visual cortex activation, two high density receive arrays and an optimized single‐voxel MEGA‐sLASER sequence with macromolecular suppression for signal acquisition.The coil setup performance as well as the GABA measurement speed, SNR, and stability were evaluated. A 2.2‐fold gain of the average SNR for GABA detection was obtained, as compared with a conventional 7 T setup. This was achieved by increasing the viewing angle of the participant with respect to the visual stimulus, thereby activating almost the entire primary visual cortex, allowing larger spectroscopy measurement volumes and resulting in an improved GABA SNR. Fewer than 16 signal averages, lasting 1 min 23 s in total, were needed for the GABA fit method to become stable, as demonstrated in three participants. The stability of the measurement setup was sufficient to detect GABA with an accuracy of 5%, as determined with a GABA phantom. In vivo, larger variations in GABA concentration are found: 14‐25%. Overall, the results bring functional GABA detections at a temporal resolution closer to the physiological time scale of BOLD cortex activation.

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Section: Discussionmentioning

confidence: 99%

Maximizing sensitivity for fast GABA edited spectroscopy in the visual cortex at 7 T

et al. 2018

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“…Difference editing techniques in particular use frequency-selective inversion pulses to achieve this (for methodological reviews, see Harris et al, 2017; Puts and Edden, 2012). The popularity of MEGA-PRESS is attributed to a number of factors, including the wide availability of the basic PRESS sequence across scanner platforms, its relatively straightforward implementation (Mullins et al, 2014), its reproducibility (Bogner et al, 2010; Brix et al, 2017; Geramita et al, 2011; Mikkelsen et al, 2016a; Near et al, 2014; O’Gorman et al, 2011; Shungu et al, 2016) and continued development of acquisition methodology and data processing tools (Chan et al, 2016; Edden et al, 2014). …”

Section: Introductionmentioning

confidence: 99%

Big GABA: Edited MR spectroscopy at 24 research sites

et al. 2017

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Magnetic resonance spectroscopy (MRS) is the only biomedical imaging method that can noninvasively detect endogenous signals from the neurotransmitter γ-aminobutyric acid (GABA) in the human brain. Its increasing popularity has been aided by improvements in scanner hardware and acquisition methodology, as well as by broader access to pulse sequences that can selectively detect GABA, in particular J-difference spectral editing sequences. Nevertheless, implementations of GABA-edited MRS remain diverse across research sites, making comparisons between studies challenging. This large-scale multi-vendor, multi-site study seeks to better understand the factors that impact measurement outcomes of GABA-edited MRS. An international consortium of 24 research sites was formed. Data from 272 healthy adults were acquired on scanners from the three major MRI vendors and analyzed using the Gannet processing pipeline. MRS data were acquired in the medial parietal lobe with standard GABA+ and macromolecule- (MM-) suppressed GABA editing. The coefficient of variation across the entire cohort was 12% for GABA+ measurements and 28% for MM-suppressed GABA measurements. A multilevel analysis revealed that most of the variance (72%) in the GABA+ data was accounted for by differences between participants within-site, while site-level differences accounted for comparatively more variance (20%) than vendor-level differences (8%). For MM-suppressed GABA data, the variance was distributed equally between site- (50%) and participant-level (50%) differences. The findings show that GABA+ measurements exhibit strong agreement when implemented with a standard protocol. There is, however, increased variability for MM-suppressed GABA measurements that is attributed in part to differences in site-to-site data acquisition. This study’s protocol establishes a framework for future methodological standardization of GABA-edited MRS, while the results provide valuable benchmarks for the MRS community.

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“…Temporal variations may have modified the correlations. Of note, coefficients of variance for the studied compounds at rest have been found to be low in healthy individuals within extended periods, suggesting limited intra-subject variability (Kirov et al, 2012;Near et al, 2014b). Reproducibility of IGT results has still to be shown.…”

Section: Discussionmentioning

confidence: 91%