Murdoch, Russell Boyd;
(2022)
Developing MRI Quantitative Susceptibility Mapping to Investigate the Effect of Sickle Cell Anaemia on Brain Magnetic Susceptibility.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Sickle Cell Anaemia (SCA) is a global health burden, characterised by complex pathology, including neurocognitive disability. This research developed MRI quantitative susceptibility mapping (QSM) methods for application in the study of SCA. QSM calculates the spatial distribution of magnetic susceptibility (χ) and is used to investigate changes in brain tissue composition and venous oxygen saturation (Yv). Whole-brain χ changes in SCA relative to healthy controls (HC) were investigated in participants recruited from UK clinical studies by registering χ maps to a study specific template. Permutation statistics identified extensive regions around the brain stem where χ was significantly elevated in SCA, suggesting increased iron accumulation with age. Phase images were retained from standard gradient echo (GRE) and multi-parametric mapping (MPM) acquisitions, an MRI technique comprising three GRE sequences. We developed a QSM pipeline to calculate χ maps from the MPM acquisitions and showed that the MPM average provided high-quality χ maps, increasing the clinical value of MPM. A comparison of QSM and T2-relaxation-under-spin-tagging (TRUST) measures of Yv in SCA, found poor correlations and significant biases, showing validation of MRI-based Yv measures in SCA is required. QSM is a promising method and found Yv was significantly diminished in SCA relative to HC, and further decreased in SCA subjects with silent cerebral infarcts (SCI) relative to those without. Significant χ differences were found between segmented SCI lesions in the frontal and occipital lobes and between lesions with different SCI definitions. This suggests that χ differences exist between lesions and QSM can be used to characterise SCI composition. QSM pipelines were developed for two GRE sequences used to image Tanzanian SCA children. We investigated regional χ changes in grey matter and found the increased χ identified in UK SCA adults was not observed in Tanzanian children, suggesting the iron accumulation occurs in older SCA subjects.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Developing MRI Quantitative Susceptibility Mapping to Investigate the Effect of Sickle Cell Anaemia on Brain Magnetic Susceptibility |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. 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 > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10150283 |
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