Reproducibility of brain MRS in older healthy adults at 7T

Abstract

To date, the majority of MRS reproducibility studies have been conducted in healthy younger adults, with only a few conducted in older adults at 3 T. With the growing interest in applying MRS methods to study the longitudinal course and effects of treatments in neurodegenerative disease, it is important to establish reproducibility in age‐matched controls, especially in older individuals. In this study, spectroscopic data were acquired using a stimulated echo acquisition mode (STEAM) localization technique in two regions (anterior and posterior cingulate cortices—ACC, PCC, respectively) in 10 healthy, cognitively normal older adults (64 ± 8.1 years). Reproducibility was assessed via mean coefficients of variation (CVs) and relative differences (RDs) calculated across two visits performed 2–3 months apart. Metabolites with high signal‐to‐noise ratio (SNR) such as NAA, tCho, and Glu had mean CVs of 10% or less and mean RDs of 15% or less across both regions. Metabolites with lower SNR such as GABA and Gln had slightly higher mean CVs of 22% or less and mean RDs of 27% or less across both regions. These results demonstrate the feasibility of acquiring MRS data at 7 T in older subjects, and establish that the spectroscopic data are reproducible in both the ACC and PCC in older, healthy subjects to the same extent as in previous studies in young subjects.

Reproducibility of Glutamate, Glutathione, and GABA Measurements in vivo by Single-Voxel STEAM Magnetic Resonance Spectroscopy at 7-Tesla in Healthy Individuals

“…Compared to Wijtenburg et al (2019b)'s 7T STEAM study, our metabolite concentrations were also lower for the most part. Glutamate was 0.10 units lower on the first day and 0.01 units higher on the second day, respectively (8.4 and 0.4%, respectively).…”

“…It may be the shorter TE of our STEAM sequence compared to Wijtenburg et al's (2019b) 7T study (6 ms compared to 14 ms) that explains our superior reproducibility, reducing signal loss due to T 2 relaxation. Notably, we used outer volume suppression to enable shorter echo times (Chen et al, 1997).…”

“…Terpstra et al (2016) did not report exact CoV figures for their 7T PCC study, but judging by their bar charts, our CoV values seem to be superior. Wijtenburg et al (2013;2019a;2019b) studied the reproducibility of brain MRS in a series of publications at 3T and at 7T in groups of volunteers who were scanned twice using several different sequences. Metabolites acquired via STEAM from the PCC at 7T were from an older cohort scanned twice 2-3 months apart using a voxel of 1.6 × 2.0 × 2.8 cm and were reported as ratios relative to total creatine (creatine + phosphocreatine) without exact quantification in water-scaled values (Wijtenburg et al, 2019b).…”

“…Reproducibility measures. Comparison to other creatine-scaled MRS studies of the PCC(Lally et al, 2016;Wijtenburg et al, 2019b).…”

Effects of different macromolecular models on reproducibility of FID‐MRSI at 7T

“…The reproducibility of brain spectroscopic methods have been investigated extensively among different field strengths and acquisition techniques. 10,[33][34][35][36][37][38][39][40][41][42][43][44] Previous short TE 7T single-voxel MRS reproducibility studies have differed in their approaches to handle the MM contributions by using either the automatic MM calculation of LCModel, 35 the group-averaged measured MM spectrum (here, full MM) as part of the basis set, 36 the inversion-based suppression of the MM signal, 10 or no MM correction at all. 34 These studies were conducted with STEAM or semi-LASER using a 3 to 27 cm 3 voxel volume and TEs ranging from 14 to 72 ms positioned in the anterior cingulate, posterior cingulate, prefrontal, or occipital cortex.…”