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E-Thesis 451 views 194 downloads

New techniques for quantification of biomarkers and metabolites by magnetic resonance imaging and spectroscopy / Christopher W. Jenkins

DOI (Published version): 10.23889/Suthesis.50804

Abstract

Since its early beginnings, almost five decades ago, MRI has revolutionised medical imaging, sustaining an active field of research into new applications, and improved understanding of the underlying mechanisms. Its complexity and flexibility, as a non-invasive imaging modality is simultaneously, an as...

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Published: 2019
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
URI: https://cronfa.swan.ac.uk/Record/cronfa50804
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first_indexed 2019-06-12T21:06:54Z
last_indexed 2019-10-21T16:56:39Z
id cronfa50804
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spelling 2019-06-13T12:12:35.6532444 v2 50804 2019-06-12 New techniques for quantification of biomarkers and metabolites by magnetic resonance imaging and spectroscopy 2019-06-12 Since its early beginnings, almost five decades ago, MRI has revolutionised medical imaging, sustaining an active field of research into new applications, and improved understanding of the underlying mechanisms. Its complexity and flexibility, as a non-invasive imaging modality is simultaneously, an asset and a challenge. Quantitative imaging provides a particular challenge due to an increased sensitivity to experimental variations. The development of accurate and robust methods for quantitative magnetic resonance requires protocols to be carefully calibrated to produce consistent results. This necessitates the use of test objects with known, stable, configurable characteristics. This thesis is aimed at the development of these test objects, and their use within quantitative imaging, spectroscopy, and the development of new techniques.First, a set of magnetic resonance test objects were created, and their relaxation properties assessed. T1 and T2 are calculated using spin, and multi-spin echo sequences respectively. Several contrast and gelling agents were assessed, and the relaxivity estimated in each case. The protocol dependence of T1 estimation methods is examined using a phantom and in-vivo study. Saturation and inversion recovery estimations are compared to variable flip angle methods, and the statistical distributions of T1 maps quantified. A series of calibrated phantom studies are conducted, assessing the analysis methods used for in-vivo magnetic resonance spectroscopy. The concentration of brain metabolites is varied within liquid and gel phantoms, and the ratio of GABA to NAA is calculated using a number of analysis tools, and in-house software.Finally, a magnetic resonance spectroscopy Hamiltonian simulator is implemented in Matlab. The simulator is utilised by collaborators in developing a quantum control framework. Optimal control is used to generate chemically selective RF pulses, and initial experimental implementations explored.The quantitative methods were found to exhibit both acquisition and analysis method dependencies. However, results were largely consistent within methodology, highlighting the need for consistency across sites to ensure valid comparison. The the-oretical development of novel RF pulses has been successful, but much work remains to approach experimental implementation. E-Thesis Magnetic resonance, MRI, MRS, spectroscopy, Quantum control, RF-pulse 31 12 2019 2019-12-31 10.23889/Suthesis.50804 COLLEGE NANME COLLEGE CODE Swansea University Doctoral Ph.D Swansea University College of science & NHS Wales 2019-06-13T12:12:35.6532444 2019-06-12T14:48:27.4275825 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Physics Christopher W. Jenkins 1 0050804-12062019145940.pdf Jenkins_Christopher_PhD_Thesis_Final.pdf 2019-06-12T14:59:40.1400000 Output 73301188 application/pdf E-Thesis – open access true 2019-06-11T00:00:00.0000000 true
title New techniques for quantification of biomarkers and metabolites by magnetic resonance imaging and spectroscopy
spellingShingle New techniques for quantification of biomarkers and metabolites by magnetic resonance imaging and spectroscopy
,
title_short New techniques for quantification of biomarkers and metabolites by magnetic resonance imaging and spectroscopy
title_full New techniques for quantification of biomarkers and metabolites by magnetic resonance imaging and spectroscopy
title_fullStr New techniques for quantification of biomarkers and metabolites by magnetic resonance imaging and spectroscopy
title_full_unstemmed New techniques for quantification of biomarkers and metabolites by magnetic resonance imaging and spectroscopy
title_sort New techniques for quantification of biomarkers and metabolites by magnetic resonance imaging and spectroscopy
author ,
author2 Christopher W. Jenkins
format E-Thesis
publishDate 2019
institution Swansea University
doi_str_mv 10.23889/Suthesis.50804
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Physics{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Physics
document_store_str 1
active_str 0
description Since its early beginnings, almost five decades ago, MRI has revolutionised medical imaging, sustaining an active field of research into new applications, and improved understanding of the underlying mechanisms. Its complexity and flexibility, as a non-invasive imaging modality is simultaneously, an asset and a challenge. Quantitative imaging provides a particular challenge due to an increased sensitivity to experimental variations. The development of accurate and robust methods for quantitative magnetic resonance requires protocols to be carefully calibrated to produce consistent results. This necessitates the use of test objects with known, stable, configurable characteristics. This thesis is aimed at the development of these test objects, and their use within quantitative imaging, spectroscopy, and the development of new techniques.First, a set of magnetic resonance test objects were created, and their relaxation properties assessed. T1 and T2 are calculated using spin, and multi-spin echo sequences respectively. Several contrast and gelling agents were assessed, and the relaxivity estimated in each case. The protocol dependence of T1 estimation methods is examined using a phantom and in-vivo study. Saturation and inversion recovery estimations are compared to variable flip angle methods, and the statistical distributions of T1 maps quantified. A series of calibrated phantom studies are conducted, assessing the analysis methods used for in-vivo magnetic resonance spectroscopy. The concentration of brain metabolites is varied within liquid and gel phantoms, and the ratio of GABA to NAA is calculated using a number of analysis tools, and in-house software.Finally, a magnetic resonance spectroscopy Hamiltonian simulator is implemented in Matlab. The simulator is utilised by collaborators in developing a quantum control framework. Optimal control is used to generate chemically selective RF pulses, and initial experimental implementations explored.The quantitative methods were found to exhibit both acquisition and analysis method dependencies. However, results were largely consistent within methodology, highlighting the need for consistency across sites to ensure valid comparison. The the-oretical development of novel RF pulses has been successful, but much work remains to approach experimental implementation.
published_date 2019-12-31T04:02:26Z
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score 11.012656

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