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Title: Hyperpolarised 129Xe magnetic resonance imaging techniques for assessment of human lung function
Author: Stewart, Neil James
ISNI:       0000 0004 5991 6945
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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Purpose: To contribute to advances in acquisition strategies for hyperpolarised 129Xe MRI of pulmonary function via: i) optimisation of 3D steady-state pulse sequences for imaging lung ventilation with 129Xe; ii) validation of 129Xe MR metrics of lung ventilation and microstructure against 3He equivalents; iii) experimental verification of the 129Xe chemical shift saturation recovery (CSSR) technique for evaluation of pulmonary gas exchange; iv) assessment of the reproducibility and experimental limitations of the CSSR technique; v) development of geometrical models of the alveoli for numerical analysis of 129Xe exchange dynamics in human lungs and substantiation of CSSR data. Methods: i) A numerical optimisation procedure for 3D balanced steady-state imaging of 129Xe gas was developed and utilised to acquire lung ventilation images with naturally-abundant xenon; ii) MR-derived 129Xe and 3He ventilation volume percentage (VV%) and apparent diffusion coefficient (ADC) measurements were compared in healthy volunteers, and patients with lung cancer and chronic obstructive pulmonary disease (COPD); iii) 129Xe CSSR was performed in healthy volunteers, and patients with systemic sclerosis (SSc), idiopathic pulmonary fibrosis (IPF); iv) CSSR reproducibility studies were performed in patients with COPD and age-matched volunteers; v) Histology and micro-CT images were employed to derive representative models of lung microstructure for finite element analysis of 129Xe gas exchange. Results: i) High quality images of pulmonary ventilation were obtained with optimised steady-state acquisitions of both 129-enriched and naturally-abundant xenon; ii) 3He and 129Xe MR-derived VV% and ADC metrics were comparable in all subjects, and reproducible in COPD patients; iii) 129Xe CSSR-derived septal thickness measurements were capable of distinguishing patients with IPF and COPD from healthy volunteers; iv) 129Xe CSSR septal thickness values were reproducible in COPD patients and age-matched volunteers; v) 2D/3D image-based models (accounting for heterogeneity of lung microstructure) resulted in qualitatively similar 129Xe exchange dynamics as compared with CSSR data, exhibiting subtle differences with 1D models. Conclusion: Hyperpolarised 129Xe shows promise for replacing 3He as a powerful MR contrast agent for assessment of pulmonary function, and providing unprecedented sensitivity to gas exchange limitation.
Supervisor: Wild, Jim M. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available