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Title: Two-dimensional spectroscopy of γ-aminobutyric acid on a clinical MRI scanner
Author: Lymer, Katherine
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2005
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This work evaluates three implementations of 2D MRS for both in-vitro and in-vivo GABA measurement on a clinical MRI scanner. Existing spectroscopy sequences were used to develop a protocol for performing 2D J-resolved MRS without a dedicated sequence. GABA was measured in-vitro at concentrations approaching normal physiological levels and volunteer results allowed assignment of the 3.01ppm GABA resonance at its J-coupling frequency (7.4Hz). However, the prolonged scan time of over two hours prevented practical application of this approach. A far more efficient method of acquiring 2D J-resolved spectra is achieved with a dedicated 2D J-resolved sequence. An optimised set of acquisition parameters was produced to allow GABA measurement with maximum SNR, and without macromolecule contamination, in 35 minutes. Since the reproducibility of the sequence must be sufficient to detect physiological changes, a formal reproducibility study was performed acquiring three measures of reproducibility at six concentrations of GABA, using a standard volume head coil, 3”- and 5”- surface coils. To our knowledge, this is the first such reproducibility study dedicated to 2D J-resolved GABA measurement, and as such, could have significant implications on the interpretation of in-vivo results. In-vivo 2D J-resolved spectra were acquired and compared well to the published results, allowing assignment of the 3.01ppm GABA (plus macromolecule) peak (J = 7.4Hz). In the first reported 2D J-resolved spectra specifically designed to reduce the macromolecular contribution by optimising the echo time range, assignment of the in-vivo 3.01ppm GABA peak was less convincing.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available