Intra‐session and inter‐subject variability of 3D‐FID‐MRSI using single‐echo volumetric EPI navigators at 3T

• Published in: Magnetic resonance in medicine Vol. 83; no. 6; pp. 1920 - 1929
• Main Authors: Moser, Philipp, Eckstein, Korbinian, Hingerl, Lukas, Weber, Michael, Motyka, Stanislav, Strasser, Bernhard, Kouwe, Andre, Robinson, Simon, Trattnig, Siegfried, Bogner, Wolfgang
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.06.2020; John Wiley and Sons Inc
• Subjects: Brain - diagnostic imaging; Coefficient of variation; concentric rings; Cortex (motor); dynamic functional magnetic resonance spectroscopic imaging; Frequency drift; Glutamine; Head; Head movement; Humans; intra‐subject reproducibility; Metabolites; Navigators; Neuroimaging; Note—Spectroscopic Methodology; Phantoms, Imaging; real time motion correction; reliability; Reproducibility; Reproducibility of Results; Stability analysis; Stability augmentation; Temporal lobe; Three dimensional motion; Tracking; Variability; intra-subject reproducibility; real time motion correction; concentric rings; dynamic functional magnetic resonance spectroscopic imaging; reliability
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.28076

Purpose In this study, we demonstrate the first combination of 3D FID proton MRSI and spatial encoding via concentric‐ring trajectories (CRTs) at 3T. FID‐MRSI has many benefits including high detection sensitivity, in particular for J‐coupled metabolites (e.g., glutamate/glutamine). This makes it highly attractive, not only for clinical, but also for, potentially, functional MRSI. However, this requires excellent reliability and temporal stability. We have, therefore, augmented this 3D‐FID‐MRSI sequence with single‐echo, imaging‐based volumetric navigators (se‐vNavs) for real‐time motion/shim‐correction (SHMOCO), which is 2× quicker than the original double‐echo navigators (de‐vNavs), hence allowing more efficient integration also in short‐TR sequences. Methods The tracking accuracy (position and B0‐field) of our proposed se‐vNavs was compared to the original de‐vNavs in phantoms (rest and translation) and in vivo (voluntary head rotation). Finally, the intra‐session stability of a 5:40 min 3D‐FID‐MRSI scan was evaluated with SHMOCO and no correction (NOCO) in 5 resting subjects. Intra/inter‐subject coefficients of variation (CV) and intra‐class correlations (ICC) over the whole 3D volume and in selected regions of interest ROI were assessed. Results Phantom and in vivo scans showed highly consistent tracking performance for se‐vNavs compared to the original de‐vNavs, but lower frequency drift. Up to ~30% better intra‐subject CVs were obtained for SHMOCO (P < 0.05), with values of 9.3/6.9/6.5/7.8% over the full VOI for Glx/tNAA/tCho/m‐Ins ratios to tCr. ICCs were good‐to‐high (91% for Glx/tCr in motor cortex), whereas the inter‐subject variability was ~11–19%. Conclusion Real‐time motion/shim corrected 3D‐FID‐MRSI with time‐efficient CRT‐sampling at 3T allows reliable, high‐resolution metabolic imaging that is fast enough for clinical use and even, potentially, for functional MRSI.