Development of abdominal MRI at 7 Tesla

Doran, Emma (2020) Development of abdominal MRI at 7 Tesla. PhD thesis, University of Nottingham.

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This thesis covers the development of abdominal magnetic resonance imaging (MRI) at the ultra-high field (UHF) of 7 Tesla (7 T). The advantages and challenges of MR imaging at 7 T are introduced alongside an overview of a parallel transmit system and its associated applications. Methods for mapping the B1+ field are outlined with a focus on the further adaptations required to obtain accurate measurements at UHF.

Radio frequency (RF) safety is a major limiting factor for body imaging at 7 T as the higher frequency can result in increased RF power deposition and potentially dangerous temperature increases in biological tissue during imaging. This heating effect is quantified by the specific absorption rate (SAR) and is particularly problematic for body MRI as traditional methods to mitigate risk result in longer scan times or the sacrifice of spatial resolution. It is important to have accurate SAR estimates to ensure subject safety and optimise imaging performance without being over-conservative. This thesis aimed to address this by developing a pipeline for performing subject-specific local SAR simulations. Both intra- and inter-subject variability in peak local SAR was investigated to assess the safety factors in place for current average power limits and to inform future MR safety decisions for body imaging at 7 T.

Development work and initial body imaging studies are presented. This includes results from high-resolution MR angiography of the kidneys, liver and abdominal wall. T2*-weighted images were also used to obtain T2* measurements in the kidneys, liver, adipose and muscle tissues together with fat-water images. Clinical applications of the developed imaging protocols and the techniques used to overcome the challenges encountered at 7 T are discussed throughout.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Gowland, P. A
Francis, S. T.
Keywords: Mangnetic resonance imaging, 7 Tesla, body imaging.
Subjects: Q Science > QC Physics > QC501 Electricity and magnetism
Faculties/Schools: UK Campuses > Faculty of Science > School of Physics and Astronomy
Item ID: 60537
Depositing User: Doran, Emma
Date Deposited: 24 Jul 2020 04:40
Last Modified: 24 Jul 2020 04:40

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