Authors
Nour Zeitouni, Laurent Ruck, Lena V Gast, Michael Uder, Arnd Dörfler, Armin M Nagel, Teresa Gerhalter
Published in
Magma (New York, N.Y.). Aug 21, 2026. Epub Aug 21, 2026.
Abstract
While most sodium (23Na) MRI studies focus on apparent tissue sodium concentration (aTSC), longitudinal (T₁) and transverse (T₂*) relaxation times may provide additional microstructural and physiological information. This study aimed to establish reference values for 23Na T₁ and bi-exponential T₂* in human lower-leg muscle at 3 T and 7 T, evaluate methodological factors influencing T₂* quantification, and assess the reproducibility of aTSC.
Twenty healthy volunteers underwent 23Na MRI of the lower leg at 3 T and 7 T using 3D stack-of-stars UTE acquisitions. T₂* was quantified from multi-echo data using bi-exponential fitting with both fixed and free short-component fractions. T₁ was measured with a saturation-recovery approach. aTSC was calculated using calibration phantoms.
T₁ increased with field strength (3 T 26.5 ± 2.0 ms; 7 T 28.1 ± 1.7 ms), while long T₂* decreased (3 T T₂l* 20.5 ± 2.9 ms; 7 T T₂l* 18.4 ± 2.5 ms). T₂* estimation depended on echo sampling and fitting assumptions. Mean aTSC was 17.5 ± 1.7 mM at 3 T and 18.5 ± 1.7 mM at 7 T, with a reproducibility coefficient of variation of 4.1%. Moderate positive correlations between field strengths were observed for short T₂*, its fraction, T₁, and aTSC.
This study provides reference values for sodium T₁ and bi-exponential T₂* relaxation in human skeletal muscle at 3 T and 7 T and demonstrates high reproducibility of aTSC across field strengths.
PMID:
42627565
Bibliographic data and abstract were imported from PubMed on 22 Aug 2026.
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