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Title: Optimising MRI magnetic susceptibility mapping for applications in challenging regions of the body
Author: Karsa, Anita
ISNI:       0000 0004 7659 9590
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2018
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Quantitative Susceptibility Mapping (QSM) is a recently developed Magnetic Resonance Imaging (MRI) technique that calculates the tissue magnetic susceptibility from MR phase images. While QSM is mostly used in brain images, it has great potential in other areas such as the head and neck where it has not yet been applied. Poorly oxygenated regions in head-and-neck tumours are expected to have a higher susceptibility due to the high concentration of paramagnetic deoxyhaemoglobin in the microvessels. Therefore, QSM could provide a non-invasive method for identifying hypoxic sites which are more resistant to radiation therapy. Therefore, the main goal of this work was to develop and optimise a QSM pipeline for the head-and-neck region. Applying the complicated processing procedure of QSM to this region is particularly challenging due to: ♦ unavoidable subject motion (e.g. swallowing), ♦ air-tissue interfaces inducing large background fields to be removed, ♦ and fatty tissue introducing an additional, chemical shift-induced phase component to the MRI signal. Moreover, as I have shown in the thesis, acquisition parameters such as image resolution and coverage of the region of interest have a substantial effect on measured susceptibilities. Therefore, tailoring the MRI acquisition is also crucial for accurate QSM in the head-and-neck region. I conducted a comprehensive optimisation of both the MRI acquisition and the QSM pipeline for head-and-neck images and addressed all the aforementioned problems. I developed and optimised a 6-minute acquisition protocol and a QSM processing pipeline. I also created a highly efficient phase unwrapping algorithm for challenging regions. Then, I showed that QSM, using the optimised protocol and pipeline, has high repeatability in the head and neck. Further, I applied this experience with a challenging region to clinical, pelvic MR images of the sacroiliac joint. I showed that bone marrow fat metaplasia has signi cantly higher susceptibility than normal bone marrow mainly due to its fat content.
Supervisor: Shmueli, K. ; Punwani, S. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available