Magnetic Resonance Spectroscopy of the Normal Cerebellum: What Degree of Variability Can Be Expected?

Abstract

The objectives of this paper are (a) to establish the reliability of relative metabolite concentrations determined with (1)H-MR spectroscopy of the cerebellum using a method appropriate to the constraints of clinical radiology and (b) to record normal values for metabolites within the cerebellum and to look for differences in metabolite concentrations between the cerebellar hemispheric white matter and the superior vermis. 3-T (1)H-MR spectra were obtained from voxels positioned in the right cerebellar hemispheric white matter and the superior vermis in 55 healthy adults (mean age 41 years, range 20 to 77) using a single voxel PRESS sequence (TR/TE = 2,000/144 ms). One volunteer (male, age 34 years) was examined in six separate sessions over a period of 3 weeks. Reliability of intra- and inter-subject metabolite fitted area ratios was determined by evaluating coefficients of variance (%). Inter- and intra-subject coefficients of variance (%) in metabolite ratios were consistently lower in the vermis (4 to 11.6) compared to those of the hemisphere (7.2 to 14.3). Cho/Cr was significantly higher in the vermis (0.83 ± 0.10) compared to the hemisphere (0.76 ± 0.11) and NAA/Cho was significantly lower in the vermis (1.19 ± 0.12) compared to the hemisphere (1.35 ± 0.16). Low inter- and intra-subject variability can be achieved when using a (1)H-MR spectroscopy technique that is appropriate to the time constraints of clinical radiology. The regional variations of Cho/Cr and NAA/Cho within the hemisphere and vermis should be considered when performing studies of diseases, which may preferentially target a particular cerebellar location.

Reproducibility and effect of tissue composition on cerebellar γ-aminobutyric acid (GABA) MRS in an elderly population

“…In addition, mean raw NAA/Cr can be derived as 1.08 in the cerebellum of elderly subjects from Zahr et al (54), whereas our mean raw NAA/Cr was 1.00 ± 0.11 in a similar VOI in the dentate nucleus. The currently reported intra-and inter-individual CVs of cerebellar NAA and Cr are also in close agreement with previous reports (58,59). It is worth noting here that different investigators, and hence different studies, may use different acquisition parameters, voxel sizes/placements and spectral quantification tools.…”

Two-site reproducibility of cerebellar and brainstem neurochemical profiles with short-echo, single-voxel MRS at 3T

“…These reproducibility issues might be related to various factors such as the quality of the raw spectral data, number of subjects studied, reference used for quantification, or the stability of the MR scanner. On the other hand, multisite studies that have used metabolite ratios (e.g., tNAA/tCr or tNAA/tCho) have reported lower within‐site CV of less than 10% . Although quantifying ratios does not require corrections for T 2 and water content and therefore is easier, it does not provide a clear understanding on how individual metabolites change under different pathological conditions.…”

Regional Striatal Cholinergic Involvement in Human Behavioral Flexibility

“…The cerebellum voxel was placed as high in the superior cerebellar vermis as possible while ensuring only cerebellar tissue was contained in the voxel. The superior cerebellar vermis was chosen as it has been shown to have the lowest variability in both intersubject and intrasubject metabolite ratios as measured with MRS at rest (Currie et al, 2013). All voxels were visually inspected to ensure minimal CSF was included in the voxels.…”