Assessing the variability of ²³Na MRI in skeletal muscle tissue: Reproducibility and repeatability of tissue sodium concentration measurements in the lower leg at 3 T

Abstract

The goal of this study was to evaluate the reproducibility and repeatability of tissue sodium concentration (TSC) measurements using 23 Na MRI in skeletal muscle tissue. 23 Na MRI was performed at 3 T on the right lower leg of eight healthy volunteers (aged 28 ± 4 years). The examinations were repeated at the same site after2 2 weeks to assess the variability over a medium-term period. Additionally, they were scanned at a second site shortly before or shortly after the first visit (within 3 weeks) to evaluate the inter-site reproducibility. Moreover, we analysed the effect of B 0 correction on the variability. Coefficients of variations (CVs) from mean TSC values as well as Bland-Altman plots were used to assess intra-site repeatability and inter-site reproducibility. In phantom measurements, the B 0 correction improved the quantitative accuracy. We observed differences of up to 4.9 mmol/L between the first and second visit and a difference of up to 3.7 mmol/L between the two different sites. The CV for the medium-term repeatability was 15% and the reproducibility CV was 9%. The Bland-Altman plots indicated high agreement between the visits in all muscle regions. The systematic bias of −0.68 mmol/L between site X and Y (P = 0.03) was slightly reduced to −0.64 mmol/L after B 0 correction (P = 0.04). This work shows that TSC measurements in healthy skeletal muscle tissue can be performed with good repeatability and reproducibility, which is of importance for future longitudinal or multicentre studies.

Combined imaging of potassium and sodium in human skeletal muscle tissue at 7 T

“…Recent studies examined the reliability and repeatability of quantitative 23 Na MRI in healthy calf muscle tissue at 3T. 34,42 Both found a high degree of agreement between scan and re-scan, with a lower coefficient of repeatability (also referred to as smallest real difference) for measurements performed on the same day than for measurements performed within 1 to several weeks. Because measured Na + concentrations in muscle tissue are highly sensitive to exercise and postural changes, a higher variation is expected when performing quantification measurements at different time points, and therefore under different physiological conditions.…”

“…Offresonances can cause signal blurring and therefore may induce quantification errors. This is of special importance if external references are used because the large susceptibility differences at the transition between reference tubes and muscle tissue might lead to strong B 0 inhomogeneities 34 . To correct for these inhomogeneities, offresonance maps were calculated using 2 echoes of both 23 Na and 39 K MR acquisitions according towith the phase unwrapped phase images ϕ 1,unwrapped and ϕ 2,unwrapped , the TEs of the double echo acquisition (TE 1 and TE 2 ), and the gyromagnetic ratios of 23 Na and 39 K, respectively (γ Na = 11.27 MHz/T, γ K = 1.99 MHz/T).…”

Fast in vivo23Na imaging and T2*mapping using accelerated 2D-FID magnetic resonance spectroscopic imaging at 3 T: Proof of concept and reliability study

“…A recent study with a similar 3D sequence, but with double echo to measure B 0 and correct for its inhomogeneity at 3T, showed a small enhancement in the results. 26 In this work, we provided an accelerated technique to conduct voxel-wise T 2 * measurements within an acceptable scan time (15 minutes) while maintaining the spatial quality. It is worth mentioning that recently a number of studies have shown the feasibility of voxel-wise T 2 * mapping in the brain using UTE 3D acquisition techniques.…”

Quantitative Imaging in Muscle Diseases with Focus on Non-proton MRI and Other Advanced MRI Techniques

“…13,35 It was shown that quantitative 23 Na MRI measurements can be performed with good repeatability and reproducibility, which is important for longitudinal studies and future multicenter trials. 36…”

“…Physical properties and expected relative in vivo SNR of selected non-proton nuclei33,56 Derived from measured water content (71%) of brain white matter. 57 c Measured23 Na concentration of healthy calf muscle tissue36 and healthy articular cartilage58 (highest23 Na content among all tissues). Measured35 Cl concentration of healthy brain white matter.…”