2026-09-21T06:11:07Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/504962021-07-05T14:03:20Zcom_1721.1_7582com_1721.1_7581col_1721.1_131022
David G. Cory.
Zhang, Guowang John, 1956-
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
2010-01-07T20:45:56Z
2010-01-07T20:45:56Z
1998
1998
http://hdl.handle.net/1721.1/50496
42255969
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1998.
Includes bibliographical references (leaves 160-164).
In this thesis, we explore the use of RF gradients in NMR imaging. RF gradients have advantages over gradients of the static magnetic field in that they are non-secular and offer more experimental freedom (for example they permit amplitude, phase and frequency variations). In the case of pure NQR imaging, RF gradients preserve an undistorted line-shape. RF gradients also present significant new challenges in both the probe design and the spin dynamics. All of these issues are addressed in this thesis. Potential applications of RF gradients include NMR imaging and RF gradient spectroscopy (where the RF gradients are used to average internal Hamiltonians and to select a unique coherence pathway). Pure NQR imaging is also a potentially exciting application due to the large spectral changes that are observed with physical modifications, such as radiation dose, pressure and temperature. Additional complications arise in pure NQR as compared to high field NMR since the principle axis system is defined by the crystal orientation rather than an external field. The RF field breaks this symmetry and introduces another level of complexity to the spin dynamics.
by Guowang John Zhang.
Ph.D.
176 leaves
eng
Massachusetts Institute of Technology
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http://dspace.mit.edu/handle/1721.1/7582
Nuclear Engineering
Magnetic resonance imaging via radio frequency gradient with examples from NMR and pure NQR
Magnetic resonance imaging via radio frequency gradient with examples from nuclear magnetic resonance phenomenon and pure nuclear quadrupole resonance
Thesis
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<Abstract>In this thesis, we explore the use of RF gradients in NMR imaging. RF gradients have advantages over gradients of the static magnetic field in that they are non-secular and offer more experimental freedom (for example they permit amplitude, phase and frequency variations). In the case of pure NQR imaging, RF gradients preserve an undistorted line-shape. RF gradients also present significant new challenges in both the probe design and the spin dynamics. All of these issues are addressed in this thesis. Potential applications of RF gradients include NMR imaging and RF gradient spectroscopy (where the RF gradients are used to average internal Hamiltonians and to select a unique coherence pathway). Pure NQR imaging is also a potentially exciting application due to the large spectral changes that are observed with physical modifications, such as radiation dose, pressure and temperature. Additional complications arise in pure NQR as compared to high field NMR since the principle axis system is defined by the crystal orientation rather than an external field. The RF field breaks this symmetry and introduces another level of complexity to the spin dynamics.</Abstract>
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