Test–Retest Reliability of the Brain Metabolites GABA and Glx With JPRESS, PRESS, and MEGA‐PRESS MRS Sequences in vivo at 3T

Abstract

Background The optimization of magnetic resonance spectroscopy (MRS) sequences allows improved diagnosis and prognosis of neurological and psychological disorders. Thus, to assess the test–retest and intersequence reliability of such MRS sequences in quantifying metabolite concentrations is of clinical relevance. Purpose To evaluate the test–retest and intersequence reliability of three MRS sequences to estimate GABA and Glx = Glutamine+Glutamate concentrations in the human brain. Study Type Prospective. Subjects Eighteen healthy participants were scanned twice (range: 1 day to 1 week between the two sessions) with identical protocols. Field Strength/Sequence 3T using a 32‐channel SENSE head coil in the PCC region; PRESS, JPRESS, and MEGA‐PRESS sequences. Assessment Metabolite concentrations were estimated using LCModel (for PRESS and MEGA‐PRESS) and ProFit2 (for JPRESS). Statistical Tests The test–retest reliability was evaluated by Wilcoxon signed‐rank tests, Pearson's r correlation coefficients, intraclass‐correlation coefficients (ICC), coefficients of variation (CV), and by Bland–Altman (BA) plots. The intersequence reliability was assessed with Wilcoxon signed‐rank tests, Pearson's r correlation coefficients, and BA plots. Results For GABA, only the MEGA‐PRESS sequence showed a moderate test–retest correlation (r = 0.54, ICC = 0.5, CV = 8.8%) and the BA plots indicated good agreement (P > 0.05) for all sequences. JPRESS provided less precise results and PRESS was insensitive to GABA. For Glx, the r and ICC values for PRESS (r = 0.87, ICC = 0.9, CV = 2.9%) and MEGA‐PRESS (r = 0.70, ICC = 0.7, CV = 5.3%) reflect higher correlations, compared with JPRESS (r = 0.39, ICC = 0.4, CV = 20.1%). Data Conclusion MEGA‐PRESS and JPRESS are suitable for the reliable detection of GABA, the first being more precise. The three sequences included in the study can measure Glx concentrations. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:1181–1191.

Repeatability and reliability of GABA measurements with magnetic resonance spectroscopy in healthy young adults

“…Measurement agreement in the dlPFC was also strong. Thresholds for interpreting CVs are rarely discussed in the MRS literature, but the current averaged CVs were far below those previously used (eg, 20% used by Baeshen et al 8 ). Additionally, BA plots revealed few outliers with no systematic trends in measurement error, further indicating strong agreement.…”

“…Averaged CVs showed moderate agreement, and BA plots revealed few outliers and no bias in measurement error. Meanwhile, rACC ICCs were in the low‐moderate range 8,55,56 …”

“…where x i is the value of the ith scan for each participant and SD is the sample SD for each participant. CVs are the most commonly reported metric in the MRS test-retest literature, 8,48 and provide an assessment of within-subject measurement agreement that is independent of the range of values in the sample.…”

“…GABA+ concentrations with MEGA-PRESS in the present study and others are likely overestimated because of macromolecular contamination, and current techniques for suppression of this contamination pose challenges. 7,8 Macromolecules may also vary with factors such as age or brain region, potentially increasing the difficulty of interpreting GABA findings. [58][59][60] Thus, improving techniques for macromolecular suppression remains a critical area for future work.…”

“…As summarized in Table 1, past research has shown moderate‐to‐strong test‐retest repeatability and reliability of GABA MRS in the cingulate cortex and OCC 8‐21 . Several additional studies have examined other areas, including motor regions, 21‐24 Broca’s area, 9 and the dlPFC, 22,25,26 among others 27‐29 …”