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Faculté des Sciences appliquées
Faculté des Sciences appliquées
MASTER THESIS
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MRI contrast in the locus cœruleus: Optimisation with multi-compartment spoiled gradient echo imaging

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Beckers, Elise ULiège
Promotor(s) : Phillips, Christophe ULiège
Date of defense : 25-Jun-2020/26-Jun-2020 • Permalink : http://hdl.handle.net/2268.2/8842
Details
Title : MRI contrast in the locus cœruleus: Optimisation with multi-compartment spoiled gradient echo imaging
Translated title : [fr] Contraste IRM au sein du locus cœruleus: Optimisation à l'aide d'imagerie par écho de gradient avec spoiler multi-compartiment
Author : Beckers, Elise ULiège
Date of defense  : 25-Jun-2020/26-Jun-2020
Advisor(s) : Phillips, Christophe ULiège
Committee's member(s) : Callaghan, Martina 
Sacré, Pierre ULiège
Vandewalle, Gilles ULiège
Language : English
Number of pages : 76
Keywords : [en] MRI
[en] Locus cœruleus
[en] Magnetisation transfer
[en] SPGR
[en] Contrast
Discipline(s) : Engineering, computing & technology > Multidisciplinary, general & others
Research unit : Wellcome Centre for Human Neuroimaging, University College of London
Target public : Researchers
Professionals of domain
Student
General public
Other
Institution(s) : Université de Liège, Liège, Belgique
University College London, London, United Kingdom
Degree: Master en ingénieur civil biomédical, à finalité spécialisée
Faculty: Master thesis of the Faculté des Sciences appliquées

Abstract

[en] The locus cœruleus (LC) is a small noradrenergic nucleus of high interest in neuroscience. As the main source of noradrenaline in the brain, it is involved in numerous cognitive functions such as arousal, attention and memory. In addition, previous studies have emphasised its relationship with the progression of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. The visualisation of the LC in magnetic resonance imaging (MRI) is realised through so-called neuromelanin-imaging in which magnetisation transfer (MT) effects are thought to be the main source of contrast. However, current researches insufficiently characterise the underlying contrast generation mechanisms given the poor understanding in the LC tissue properties. Efficiently visualising the locus c\oe ruleus is therefore a challenging process that requires further investigation.

The aim of this thesis is to provide an efficient tool for better understanding the underlying contrast mechanisms in the LC and thereby optimising its visualisation through multi-compartment spoiled gradient echo (SPGR) imaging. Firstly, the simulation of such a sequence through the extended phase graph with exchange (EPG-X) framework is performed in order to determine optimal sequence parameter values. After an experimentation phase, the outcomes are validated against the developed model. Simulation suggests that an optimal contrast can be achieved by maximising the power of the excitation pulse. It is expected that the use of optimal sequences compared to the one currently played out at the Wellcome Centre for Human Neuroimaging (WCHN) would improve the LC visualisation. Nonetheless, the lack of robust validation prevent the generalisation of these observations. Secondly, the SPGR model is extended by including a saturation pre-pulse for amplifying the MT effects. The contrast optimisation is realised through simulation according to the same formalism as previously while accounting for the MT pre-pulse. Optimal parameter values suggest that an improvement is achievable regarding the MT-weighted sequence currently played out through the maximisation of the power and the off-resonance frequency of the MT pulse as well as the time delay between the saturation and excitation pulses. Unfortunately, no validation was achievable for this configuration which should be investigated in future researches.

Because of the lack of knowledge about the contrast mechanisms in the LC, the optimisation of an MRI sequence effectively targeting the LC is complex. Therefore, due to the numerous parameters involved and the poor confidence regarding their impact, future studies should focus on a better characterisation of this structure and the inherent contrast mechanisms.


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Author

  • Beckers, Elise ULiège Université de Liège > Master ing. civ. biomed., à fin.

Promotor(s)

Committee's member(s)

  • Callaghan, Martina
  • Sacré, Pierre ULiège Université de Liège - ULiège > Dép. d'électric., électron. et informat. (Inst.Montefiore) > Robotique intelligente
    ORBi View his publications on ORBi
  • Vandewalle, Gilles ULiège Université de Liège - ULiège > Département de chimie (sciences) > Département de chimie (sciences)
    ORBi View his publications on ORBi
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  • Total number of downloads 484










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