Item – Theses Canada

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OCLC number
46509901
Author
Peters, Robert D.(Robert Donald),1970-
Title
An implementation of wavelet-transform encoding in magnetic resonance imaging.
Degree
M. Sc. -- University of Toronto, 1995
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, 1996.
Description
2 microfiches.
Notes
Includes bibliographical references.
Abstract
This thesis explores an alternative to standard Fourier magnetic resonance imaging (MR) called wavelet-transform encoding. The first documented implementation of wavelet-encoding on a clinical 1.5 T MRI system is described, in which spatially-selective radiofrequency pulse are used to excite slice profiles in the shape of the wavelet-basis functions of a discrete wavelet transform. Wavelet encoding is used to resolve one spatial dimension, with conventional frequency encoding and slice selection in orthogonal directions, to generate 2-D single-slice MR images. In this work, we describe controlled experiments to monitor the excitation, scaling, and translation of slice profiles in the shape of Lemarie-Battle wavelet-basis functions. Practical issues, such as corrections of the wavelet-encoded data are discussed. The wavelet transform is described as a method for multiresolution analysis and we show how a high-resolution MR image can be constructed from lower-resolution images which represent the approximation and detail structures of the object. Multilevel wavelet-encoded images of a gel phantom are presented which show no degradation in image quality compared to Fourier-encoded images of similar signal-to-noise ratio. A chemical-shift artifact is identified as a consequence of the method for scaling the wavelet-shaped slice profiles. We conclude that this static implementation of wavelet encoding lacks practicality because of poor SNR performance. However, prospective future work is described in which wavelet encoding is used in the dynamic acquisition of MR images.
ISBN
061207577X
9780612075771