Comprehensive Account of Sodium Imaging and Spectroscopy for Brain Research.

Sodium (Na) is a vital component of neuronal cells and plays a key role in various signal transmission processes. Hence, information on sodium distribution in the brain using magnetic resonance imaging (MRI) provides useful information on neuronal health. Na MRI and MR spectroscopy (MRS) improve the diagnosis, prognosis, and clinical monitoring of neurological diseases but confront some inherent limitations that lead to low signal-to-noise ratio, longer scan time, and diminished partial volume effects. Recent advancements in multinuclear MR technology have helped in further exploration in this domain. We aim to provide a comprehensive description of Na MRI and MRS for brain research including the following aspects: (a) theoretical background for understanding Na MRI and MRS fundamentals; (b) technological advancements of Na MRI with respect to pulse sequences, RF coils, and sodium compartmentalization; (c) applications of Na MRI in the early diagnosis and prognosis of various neurological disorders; (d) structural-chronological evolution of sodium spectroscopy in terms of its numerous applications in human studies; (e) the data-processing tools utilized in the quantitation of sodium in the respective anatomical regions.