PURPOSE: Spectral editing is the most common MRS approach for noninvasive in vivo measurement of low-concentration, strongly overlapped metabolites in the brain, such as γ-aminobutyric acid (GABA) and glutathione (GSH). Multi-metabolite editing methods, such as HERMES and HERCULES, enable the editing of multiple J-coupled metabolites in a single acquisition without increasing the total scan time. Yet little is known regarding the reliability of these methods. This study assessed the test-retest reliability of HERMES and HERCULES, where volume localization was achieved using both PRESS and sLASER.

METHODS: Sixteen healthy adult volunteers were scanned twice in two separate sessions. Single-voxel edited MRS data were acquired in the medial parietal lobe using the following sequences: (1) HERMES-PRESS; (2) HERMES-sLASER; (3) HERCULES-PRESS; (4) HERCULES-sLASER. Spectra were processed and metabolites were quantified relative to tCr. Data quality metrics and reliability statistics were estimated for all four acquisitions.

RESULTS: HERMES-sLASER produced lower within-subject coefficients of variation (CVws) for GABA + co-edited macromolecules (GABA+), GSH, glutamine (Gln), myo-inositol (mI), NAA, and total Cho (tCho), suggesting improved reliability compared to HERMES-PRESS. HERCULES-sLASER produced better reliability than HERCULES-PRESS for GABA+, GSH, aspartate, Gln, lactate, mI, NAA, and tCho with lower CVws. N-acetylaspartylglutamate (NAAG) showed higher CVws for HERCULES-sLASER, and Glu showed higher CVws for HERMES-sLASER and HERCULES-sLASER. Overall, these findings suggest that sLASER yields lower within-subject variability than PRESS for several metabolites for both HERMES and HERCULES, supporting improved measurement reliability.

CONCLUSION: sLASER yielded better test-retest reliability than PRESS for most metabolites than for multi-metabolite edited MRS.