Low Field MRI and the Development of Polarized Nuclear Imaging (PNI)-A New Imaging Modality

Zheng, Yuan, Physics - Graduate School of Arts and Sciences, University of Virginia
Cates, Gordon, Department of Physics, University of Virginia
Miller, Grady, Department of Radiology, University of Virginia

In this thesis, we used the technique of Spin-Exchange Optical Pumping (SEOP) to produce hyperpolarized noble gases. We studied the pressure and temperature dependence of Xe-129 polarization by making a series of cells with different gas compositions and measuring the Xe polarization over a large temperature range.
We constructed a low field MRI scanner for hyperpolarized noble gases. Our scanner was built with off-the-shelf electronics and co-axial circular coils. We imaged both He-3 and Xe-129 samples. Using a fully phase encoded pulse sequence and with some auxiliary measurements, we acquired a high quality image with Xe-129 at low field (2 mT).
We developed genuinely new techniques of Polarized Nuclear Imaging (PNI) and Polarized Nuclear Detection (PND), which make use of the asymmetric radioactive emissions of certain polarized radioactive nuclei. In these techniques, the nuclear spins are manipulated using conventional Nuclear Magnetic Resonance (NMR) methods. However, instead of detecting radio-frequency electromagnetic waves, single photons (or other types of radioactive emissions) are detected. As a result, the signal detection sensitivity is greatly enhanced. We also developed the novel Cates-Miller-Zheng (CMZ) pulse sequence class that is specially suited for PNI, and successfully acquired a preliminary image of a Xe-131m sample.

PHD (Doctor of Philosophy)
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