Comprehensive Account of Sodium Imaging and Spectroscopy for Brain Research

Abstract

Sodium ( 23 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. 23 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 23 Na MRI and MRS for brain research including the following aspects: (a) theoretical background for understanding 23 Na MRI and MRS fundamentals; (b) technological advancements of 23 Na MRI with respect to pulse sequences, RF coils, and sodium compartmentalization; (c) applications of 23 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 dataprocessing tools utilized in the quantitation of sodium in the respective anatomical regions.

Advances in Stimuli‐Responsive Chitosan Hydrogels for Drug Delivery Systems

“…Ion strength‐responsive property is essential in the anti‐cancer drug delivery systems because changes in the concentration of sodium ions in vivo may be ascribed to the presence of cancer cells. [ 75 ] Typically, hydrogels with ionic networks are known to be affected by alterations in the ion strength of the aqueous solution, resulting in protonation or deprotonation. By varying the ionic strength, the reversibility of the hydrogel can be exploited to tune the release of the encapsulated drug.…”

Sodium Dynamics in the Cellular Environment

“…23 Na nuclear magnetic resonance (NMR) is a noninvasive yet highly specific analytical technique that can probe the physiochemical state and map the concentration of sodium. 23 Na MR imaging (MRI) has been adapted in various clinical studies in the brain, musculoskeletal tissues, cancers, and so on. − Most of the studies are based on the measurement of total sodium concentration to diagnose the pathological state of target tissues. − As a stage further, the distinction of intra- and extracellular sodium ions and the knowledge about their dynamics and binding states could offer more details of the physiological functions or pathological characters. The fine characterization of biological sodium can be anchored on the NMR properties including chemical shifts, diffusivity, and relaxation.…”