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Title: Motion estimation using radiofrequency scattering of a parallel transmit coil for cardiac magnetic resonance imaging at 7T
Author: Jaeschke, Sven
ISNI:       0000 0004 8507 0912
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2019
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Magnetic resonance imaging (MRI) at ultra-high magnetic field strengths offers an increased signal-to-noise ratio (SNR) and has the potential to boost the MR image resolution. Cardiovascular applications remain challenging, as high-resolution image acquisitions are still too slow to capture a fast moving organ like the heart. Synchronisation of the acquisition to the heart motion is necessary to acquire an image over several consecutive heartbeats. The current gold-standard method for cardiac synchronisation is the electrocardiogram (ECG), which measures the electrical activity of the heart. Magnetohydrodynamic effects of the blood flow interfere with the ECG measurement and can affect reliable gating, which is particularly significant at higher magnetic field strengths. The work of this thesis presents new motion estimation methods that are based on radiofrequency (RF) scattering of a parallel-transmit coil and directly assess the heart motion, independent of the electrical activity of the heart. A cardiac motion signal is derived with a high SNR and with a number of potential gating features, which have a high accuracy when compared to ECG gating. No additional motion-monitoring hardware is needed other than the commercially available pTx system. Different RF pulse designs are proposed to integrate the scattering measurements into the normal MR image acquisition to estimate cardiac and respiratory motion in real-time on the MRI scanner. The integrated cardiac-respiratory motion framework is combined with a new MR imaging acquisition strategy to acquire high-resolution, 3D images of the heart during free breathing.
Supervisor: Hess, Aaron ; Robson, Matthew Sponsor: Medical Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Magnetic resonance imaging ; Cardiology