eprintid: 1426205 rev_number: 65 eprint_status: archive userid: 608 dir: disk0/01/42/62/05 datestamp: 2014-10-10 07:30:10 lastmod: 2022-01-12 00:01:54 status_changed: 2014-10-10 07:30:10 type: thesis metadata_visibility: show item_issues_count: 0 creators_name: Richardson, S title: A Viable Isolated Tissue System: A Tool for Detailed MR Measurements and Controlled Perturbations in Physiologically Stable Tissue ispublished: unpub divisions: UCL divisions: B02 divisions: C07 divisions: D07 divisions: F83 divisions: C10 divisions: D17 divisions: G94 divisions: B04 divisions: C05 divisions: F48 keywords: MRI, Diffusion MRI, Viable Isolated Tissue, Additive Layer Manufacturing, Chemical Fixation, Functional Diffusion MRI, Modelling abstract: The research presented in this thesis revolves around developing, testing and applications of a tool for the development and assessment of diffusion weighted MRI and methods. The tool is a viable isolated tissue (VIT) maintenance chamber. The chamber was designed to maintain a section of rat optic nerve white matter in a stable state, as close to in vivo conditions as possible, while removing all of the confounding problems of imaging such tissue in a live animal. The chamber was designed to fit into a small volume coil in a high field horizontal bore MRI scanner and to enable extended periods of in depth, detailed experimentation. Additive layer manufacturing was used to construct the chamber. A series of validation experiments were conducted to demonstrate the performance of the chamber and the stability of optic nerves maintained within it. Fixed samples have been used extensively in diffusion MRI (dMRI) studies. However, fixation causes significant structural changes in tissue. The chamber was used to evaluate fixed white matter as a surrogate for viable white matter during development and validation of dMRI methods. Diffusion tensors and multi-compartment white matter signal models were fit to the data. The data demonstrated that fixed tissue, while maintaining the broad water environment of viable tissue, differs significantly in diffusion parameters. The chamber was further developed to enable in MRI electrophysiological stimulation and recording from the rat optic nerve. This EP-MRI chamber was designed to enable investigation of the existence of a dMRI measurable structural change in the tissue upon electrical activation. The functional diffusion MRI (dfMRI) signal could be more specific to in vivo functional activation that the gold-standard fMRI method which measures blood oxygenation levels to produce contrast. Preliminary data suggests that a purely structural dfMRI effect, though marginal, may be present in this simplified system. date: 2014-05-28 vfaculties: VGHCSCI vfaculties: VENG vfaculties: VENG oa_status: green full_text_type: other thesis_class: doctoral_open language: eng thesis_view: UCL_Thesis dart: DART-Europe primo: open primo_central: open_green verified: verified_manual elements_source: Manually entered elements_id: 940359 language_elements: EN lyricists_name: Alexander, Daniel lyricists_name: Lythgoe, Mark lyricists_name: Richardson, Simon lyricists_name: Siow, Bernard lyricists_id: DALEX06 lyricists_id: MFLYT72 lyricists_id: SRICH17 lyricists_id: BSIOW77 full_text_status: public pagerange: 1 - 162 pages: 162 institution: UCL (University College London) department: Medical Physics and Bioengineering thesis_type: Doctoral editors_name: Alexander, DC editors_name: Lythgoe, editors_name: Siow, citation: Richardson, S; (2014) A Viable Isolated Tissue System: A Tool for Detailed MR Measurements and Controlled Perturbations in Physiologically Stable Tissue. Doctoral thesis , UCL (University College London). Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/1426205/1/Richardson_Simon__Thesis_Final_SR.pdf