Keywords
21• Magnetic resonance spectroscopy 22 Highlights 25 • Means and CVs for tNAA and tCho are highly consistent across vendors and algorithms. 26• Means and CVs for mI and Glx are less consistent across vendors and algorithms. 27• Agreement between metabolite estimates from different algorithms is moderate at best. 28• Baseline estimation contributes significantly to measurement variance. 29Abstract 30 Short-TE proton magnetic resonance spectroscopy is commonly used to study metabolism in the 31 human brain. Spectral modelling is a crucial analysis step, yielding quantitative estimates of me-32 tabolite levels. Commonly used quantification methods model the data as a linear combination of 33 metabolite basis spectra, maximizing the use of prior knowledge to constrain the model solution. 34 Various linear-combination modelling (LCM) algorithms have been integrated into widely used 35 commercial and open-source analysis programs. 36This large-scale, in-vivo, multi-vendor study compares the levels of four major metabolite com-37 plexes estimated by three LCM algorithms (Osprey, LCModel, and Tarquin). 277 short-TE spec-38 tra from a recent multi-site study were pre-processed with the Osprey software. The resulting 39 spectra were modelled with Osprey, Tarquin and LCModel, using the same vendor-specific basis 40 sets. Levels of total N-acetylaspartate (tNAA), total choline (tCho), myo-inositol (mI), and gluta-41 mate+glutamine (Glx) were quantified with respect to total creatine (tCr). 42Mean spectra and models showed high agreement between all vendors and LCM algorithms. In 43 contrast, the algorithms differed notably in their baseline estimates and mI models. Group means 44 and CVs of the metabolite estimates agreed well for tNAA and tCho across vendors and algo-45 rithms. For mI and Glx, group means metabolite estimates and CVs agreed less well between 46 algorithms, with mI systematically estimated lower by Tarquin. Across all datasets, the metabo-47 lite-mean CV was 10.4% for Osprey, 12.6% for LCModel, and 14.0% for Tarquin. The grand 48 mean correlation coefficient for all pairs of LCM algorithms across all datasets and metabolites 49 was R 2 = 0.39, indicating generally moderate agreement of individual metabolite estimates be-50 tween algorithms. Stronger correlations were found for tNAA and tCho than for Glx and mI. 51 Correlations between pairs of algorithms were comparably moderate (Tarquin-vs-LCModel: R 2 52 = 0.43; Osprey-vs-LCModel: R 2 = 0.38; Osprey-vs-Tarquin: R 2 = 0.37). There was a signifi-53 cant association between local baseline power and metabolite estimates (grand mean R 2 = 0.10; 54 up to 0.62 for LCModel analysis of Glx in Siemens datasets). Metabolite estimates with stronger 55 associations to the local baseline power (mI and Glx) showed higher variance, suggesting that 56 baseline estimation has a stronger influence on those metabolites than on tNAA and tCho. 57While estimates of major metabolite complexes broadly agree between linear-combination mod-58 elling algorithms at group ...