Title:
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Quantitative MRI for measuring myelin content in human spinal cord
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The aim of this thesis is to progress the state-of-the art of quantitative Magnetic Resonance Imaging (MRI) in the human spinal cord, with particular focus on methods sensitive to myelin content. Myelin is a fundamental structure of the central nervous system, ensuring the correct transmission of action potentials along neuronal axons, affected in a number of neurological disorders, first and foremost Multiple Sclerosis (MS). MRI methods to assess myelin in the spinal cord have found limited development, despite the primary involvement of the spinal cord in demyelinating diseases, such as MS where the characterization of spinal cord pathology is key for a better diagnosis, understanding of pathological processes, and evaluation of neuroprotective and reparative treatments. In this thesis, we develop novel methods for the spinal cord to measure parameters that are known to correlate with myelin content, namely the longitudinal relaxation time (T1) and quantitative Magnetization Transfer (qMT) parameters, and we compare them with a large set of myelin sensitive MRI indices in the post mortem MS spinal cord. The thesis is structured as follows: chapter 1 states the problem this thesis attempts to address and provides background information regarding the involvement of the spinal cord in MS; chapter 2 reviews the basic principles of MRI and introduces the theory behind the measurement of surrogate indices of myelin content with MRI; chapter 3 reviews an existing imaging sequence for the spinal cord, extends its use for measuring myelin sensitive parameters and discusses potential improvements for in vivo applications; chapter 4 and chapter 5 propose novel efficient methods to measure T1 and qMT parameters in vivo in the spinal cord; and chapter 6 evaluates the performance of the methods developed in the previous chapter, together with other prospective myelin mapping methods, in the healthy and MS post mortem human spinal cord.
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