Application of synthesis arrays to MRI flow measurement using the RF phase gradient technique /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1993.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Radio Frequency (RF) phase gradients in the receiver coil field pattern can encode flow velocity information in magnetic resonance (MR) images in the form of phase variations. These phase variations are not readily observed in MR images because they are relatively small compared to phase variations caused by magnetic field inhomogeneities, susceptibility variations, and other sources. However, the phase contributions from these other sources are independent of the receiver coil. Therefore, the RF phase gradient encoded flow information can be recovered by subtracting images obtained simultaneously using arrays of independent receiver coils and a multiple channel receiver. This flow velocity information can be extracted retrospectively from standard imaging sequences, including flow-compensated sequences. No additional time is required for the flow study as the flow measurements are made using sequences chosen for optimal imaging, and the images from each coil are obtained simultaneously. Results indicate that sufficient sensitivity is obtained to make flow measurements in the range of velocities commonly found in the carotid arteries and other major vessels. In principle, the method works with as few as two receiver coils. However, additional elements provide additional phase measurements that can be used to increase accuracy, remove ambiguities in flow direction or velocity calculations, and increase the region over which velocity measurements can be accurately made. This study lays the theoretical background for the method of flow measurement using the RF phase gradients, describes and documents its capabilities via experimentations, develops a statistical technique to estimate its accuracy, discusses methods of increasing the accuracy by creating a more rapid phase change, and finally provides several examples to prove its applicability. |
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| Item Description: | Vita. "Major subject: Electrical Engineering." |
| Physical Description: | xv, 226 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |