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Sodium Imaging

Sodium is one of the most important ions for the physiology of the cell and it has an essential role in a variety of cellular functions. In healthy tissue, sodium is present in the intracellular and in the extracellular compartments at highly regulated concentrations of about 10 mmol/l and 150 mmol/l, respectively.

Deviations in the sodium concentration from these levels are indicative of diseases that involve metabolic changes and/or alter the normal function of the sodium-potassium pump. Sodium is the second most abundant MR-active nucleus in tissues and past work has shown that the average tissue sodium concentration (TSC) measured by sodium MRI correlates with a variety of diseases making it an ideal means to monitor pathologies in vivo. Accordingly, there is a strong motivation for the pursuit of 23Na MRI.

Difficulties such as the fast, biexponential transverse relaxation of the sodium MR signal and the low MR sensitivity of the 23Na nucleus, preclude the use of most standard MRI techniques.

The sodium imaging team is developing novel approaches for the study of the distribution and the relaxation times of the sodium ion in the brain.

Projects

Comparison of methods for in vivo sodium imaging at 9.4 Tesla

Comparison of methods for in vivo sodium imaging at 9.4 Tesla

The sodium nucleus exhibits a fast biexponential signal decay. Thus sequences with ultra short echo times are required to improve sensitivity.

Multiple-Quantum Coherence Methods

Multiple-Quantum Coherence Methods

Changes in intracellular sodium levels are closely linked to cell viability. Triple-quantum filtering offers a contrast that is especially sensitive to intracellular sodium concentration.

SPRITE Imaging

SPRITE Imaging

A novel approach for in vivo sodium imaging is the use of the SPRITE imaging sequence: a pure phase-encoding MRI technique typically used to image solid state samples.

Measurement of Relaxation Times

Relaxation Measurements

In contrast to the proton nucleus (spin 1/2), the sodium nucleus has a spin of 3/2. It can have three transitions, each with a different relaxation rate. In solution the relaxation behaviour is mono exponential, but in the presence of macro molecules relaxation becomes, due to the quadrupolar interaction, biexponential


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