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Title: A study of field cycling on a low field magnetic resonance imager
Author: Baras, Panagiotis
ISNI:       0000 0001 3443 7583
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1997
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Field Cycled Magnetic Resonance Imaging offers potential for significant Signal to Noise Ratio and T1 contrast improvements of Magnetic Resonance images. In this work the hardware and software components of a home made, low field NMR imager were modified, in order to investigate Field Cycling. Theoretical models were developed to simulate NMR signal response to different magnetic field pulse shapes and it was seen that trapezoidal magnetic field pulse waveforms, with rise/fall times considerably smaller than the T1 relaxation times of the examined samples, give comparable results to those of an ideal, rectangular pulse. The steady state signal expressions of Field Cycled Gradient Echo and Spin Echo sequences were derived and tested experimentally. Differences between theoretical and experimental results can be attributed to the increased levels of noise and the effect of time dependent magnetic fields due to limited efficiency of the induced current cancelling scheme. The ability of the imager to measure T1 relaxation times at different magnetic field strengths, employing Field Cycled imaging sequences, was also assessed. Results were again burdened by the above mentioned problems, as well as, by the considerable temperature changes the samples suffered during the long imaging times required for complete study.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Medical imaging Pattern recognition systems Pattern perception Image processing Biophysics