Rot, Samuel Sándor;
(2024)
Novel Methods for Quantitative Sodium MRI AT 3T and 7T.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Sodium magnetic resonance imaging (²³Na MRI) captures the nuclear magnetic resonance signal of sodium ions in vivo, providing unique insights into their essential physiological and metabolic processes. Despite low signal-to-noise ratio (SNR) and rapid signal decay, developments in the last decades have enabled acquisitions of good quality sodium images, on 3T MR systems, in under 20 minutes. ²³Na MRI usually quantifies the total sodium concentration (TSC) metric, encompassing both intra- and extracellular compartments. Although TSC is sensitive to many pathologies, the metric has limitations. Firstly, there is great variability in reported TSC of healthy brains, with the underlying sources unclear. Further, due to cellular volume fractions, interpretation of TSC alterations can be ambiguous. Lastly, conventional TSC quantification is not suitable for probing the crucial role of sodium ions in neuronal excitation and function. This thesis aimed to advance quantitative ²³Na MRI by addressing the aforementioned limitations. The first part laid the groundwork by developing two advanced acquisition schemes for ²³Na MRI at 3T. Secondly, a novel, synthetic phantom for in vivo TSC quantification was developed and tested at 3T, contributing towards methods harmonisation of TSC measurement. Thirdly, methods for whole-brain mapping of biexponential ²³Na T₂* were implemented using a 7T system equipped with a multichannel coil, which posed a challenge for image reconstruction and T₂* fitting. Complementary measurement of T₂∗ may aid meaningful interpretation of TSC, as tested in a pilot study of paediatric non-structural epilepsy. Finally, at 3T, a protocol for rapid acquisitions was applied to explore ²³Na MRI in studying healthy brain function, with inconclusive results. The above findings, and this thesis, form an important contribution towards the present understanding and methods of quantitative ²³Na MRI, shaping future studies and applications at both 3 T and ultrahigh fields.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Novel Methods for Quantitative Sodium MRI AT 3T and 7T |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10200227 |
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