This thesis is focussed on extending the use of phased array radiofrequency (RF) coils for use in magnetic resonance imaging (MRI). Phased arrays are very useful as receiver coils and have been used over the last 15 years or so to improve receiver coil coverage and to speed up image acquisition. These arrays have almost invariably been constructed and used at mid- to highfrequency (<128 MHz), thus there is clearly an opportunity to increase the operating frequency of the phased array and also use these systems in transceive mode. Using phased array coils in transceive mode has the advantage of gaining better spatial specificity of excited regions. Also as the operating wavelength in high field strength is shortened by the dielectric properties of the patient and approaches the size of conventional transmitter coils, there are distinct advantages in using the smaller coils in the phased array system for transmission. In addition, with the ability to independently control the magnitudes and phases of the transmission power on each element of a transceiver phased array system, RF focussing or shimming can be performed during RF transmission. The research work presented in this thesis is therefore, primarily focussed on designing and analysing high frequency phased array coils for MRI applications with transceive and RF focussing capability and investigating the possibility of using focussing transceive phased array coils to ameliorate image distortions that appear in high field MR images. The second major area of work concerns evaluation of the performance of partial parallel imaging when used at high field strength and the compatibility with transceive phased array systems. Common to both areas are investigation into other approaches for the design of high field RF coils, exploring the possibility of new mutual decoupling techniques and the consideration of other numerical computational methods that can assist in designing future high frequency phased array coils and help evaluate the complex field-tissue interactions at high field strength.
| Identifer | oai:union.ndltd.org:ADTP/290318 |
| Creators | Li, Bing Keong Joe |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
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