The technique of functional magnetic resonance imaging is rapidly moving from one of technical interest to wide clinical application. However, there are a number of questions regarding the method that need resolution. Some of these are investigated in this thesis.
High resolution fMRI is demonstrated at 3.0 T, using an interleaved echo planar imaging technique to keep image distortion low. The optimum echo time to use in fMRI experiments is investigated using a multiple gradient echo sequence to obtain six images, each with a different echo time, from a single free induction decay. The same data are used to construct T2* maps during functional stimulation. Various techniques for correcting the N/2 ghost are tested for use in fMRI experiments, and a method for removing the image artefact caused by external r.f. interference in a non-linearly sampled matrix is presented.
The steps in the analysis of fMRI data are detailed, and two new non-directed analysis techniques, particularly for data from single events, as opposed to epoch based paradigms, are proposed. The theory behind software that has been written for fMRI data analysis is also given.
Finally, some of the results from an fMRI study into the initiation of movement are presented, illustrating the power of single event experiments in the separation of cognitive processes.
I would like to thank my supervisors, Prof. Peter Morris and Dr. Richard Bowtell, for the support and advice they have provided throughout the duration of my Ph.D. I am also indebted to Dr. Jon Hykin for teaching me the art of functional MRI and to Dr. Miles Humberstone for providing the impetus for much of my work. I would also like to thank all the people with whom I have worked over the past three years without whom none of this work could have been done, and particularly those who have patiently laid in the scanner for my experiments. Finally I would like to thank the University of Nottingham for their funding.
I would also like to thank Peter Hobden (FMRIB, University of Oxford) for generating new graphics for some of the figures in this thesis, particularly in Chapter 3.