Kiersnowski, Oliver C;
(2023)
Optimising MRI Quantitative Susceptibility Mapping Techniques for Clinical Translation and Accelerated Structural and Functional Research Applications.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Quantitative susceptibility mapping (QSM) is a magnetic resonance imaging (MRI) technique that utilises the phase of the complex MRI signal and a physics-based reconstruction pipeline to estimate the underlying tissue susceptibility distribution. QSM provides information on tissue composition such as iron content affected in several neurodegenerative diseases. The gold-standard sequence for acquiring data for QSM is a 3D gradient echo (GRE) sequence, with a whole-brain acquisition time of approximately 5 minutes. Echo planar imaging (EPI) sequences can acquire whole-brain volumes in a few seconds, allowing both structural and functional neuroimaging. I present work on translating QSM into clinical practice through investigating the effects of oblique slice acquisition, developing a robust method to correct for tilted slices or volumes. I also developed and optimised a robust QSM acquisition protocol and QSM reconstruction pipeline for neuroradiological imaging of patients with movement disorders; neuroradiologist scores based on image quality demonstrated their preference for iterative Tikhonov and Auto non-linear dipole inversion (NDI) susceptibility calculation methods over total variation-based regularised methods. I optimised a QSM reconstruction pipeline for investigations into tissue composition changes in patients with temporal lobe epilepsy (TLE), to find susceptibility and R2* differences in TLE patients compared to healthy controls, affecting the hippocampus, amygdala, thalamus and basal ganglia. A major portion of my research was to optimise the QSM acquisition and reconstruction pipeline for a multi-echo 2D EPI sequence for rapid (< 4 s repetition time) structural and functional QSM. This included: investigating the use of simultaneous multi-slice (SMS) acceleration which was found to provide accurate and rapid EPI-QSM; comparing single-echo and multi-echo EPI acquisitions for QSM; developing methods to reduce geometric distortion inherent to EPI sequences; and reducing artefacts in reconstructed susceptibility maps through optimising the QSM pipeline for multi-echo 2D-EPI. I applied the results of these investigations to present optimised structural QSM, preliminary functional QSM and functional MRI (fMRI) results from a 1.3 mm isotropic resolution multi-echo EPI sequence with 3-fold SMS and 4-fold GRAPPA acceleration.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Optimising MRI Quantitative Susceptibility Mapping Techniques for Clinical Translation and Accelerated Structural and Functional Research Applications |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. 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. |
| Keywords: | Quantitative susceptibility mapping, QSM, Echo planar imaging, EPI, Clinical translation |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS 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 |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10183385 |
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