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3D radial projection technique with ultrashort echo times for sodium MRI: clinical applications in human brain and skeletal muscle.

S. Nielles-Vallespin, M. Weber, M. Bock, A. Bongers, P. Speier, S. Combs, J. Wöhrle, F. Lehmann-Horn, M. Essig and L. Schad

Magn Reson Med, 57 (1), pp.74-81

(23)Na MRI has the potential to noninvasively detect sodium (Na) content changes in vivo. The goal of this study was to implement (23)Na MRI in a clinical setting for neurooncological and muscular imaging. Due to the biexponential T(2) decay of the tissue Na signal with a short component, which ranges between 0.5-8 ms, the measurement of total Na content requires imaging techniques with echo times (TEs) below 0.5 ms. A 3D radial pulse sequence with a TE of 0.2 ms at a spatial resolution of 4 x 4 x 4 mm(3) was developed that allows the acquisition and presentation of Na images on the scanner. This sequence was evaluated in patients with low- and high-grade gliomas, and higher (23)Na MR signals corresponding to an increased Na content were found in the tumor regions. The contrast-to-noise ratio (CNR) between tumor and white matter increased from 0.8 +/- 0.2 to 1.3 +/- 0.3 with tumor grade. In patients with an identified muscular (23)Na channelopathy (Paramyotonia congenita (PC)), induced muscle weakness led to a signal increase of approximately 18\% in the (23)Na MR images, which was attributed to intracellular Na(+) accumulation in this region.