Distant dipolar field (DDF)-based nuclear magnetic resonance is an active research area with many fundamental properties still not well understood. Already several intriguing applications have developed, like HOMOGENIZED and IDEAL spectroscopy, that allow high resolution spectra to be obtained in inhomogeneous fields, such as in-vivo. The theoretical and experimental research in this thesis concentrates on the fundamental signal properties of DDF-based sequences in the presence of relaxation (T1 and T2) and diffusion. A general introduction to magnetic resonance phenomenon is followed by a more in depth introduction to the DDF and its effects. A novel analytical signal equation has been developed to describe the effects of T2 relaxation and diffusing spatially modulated longitudinal spins during the signal build period of an HOMOGENIZED cross peak. Diffusion of the longitudinal spins results in a lengthening of the effective dipolar demagnetization time, delaying the re-phasing of coupled anti-phase states in the quantum picture. In the classical picture the unwinding rate of spatially twisted magnetization is no longer constant, but decays exponentially with time. The expression is experimentally verified for the HOMOGENIZED spectrum of 100mM TSP in H2O at 4.7T. Equations have also been developed for the case of multiple repetition steady state 1d and 2d spectroscopic sequences with incomplete magnetization recovery, leading to spatially varying longitudinal magnetization. Experimental verification has been accomplished by imaging the profile. The equations should be found generally applicable for those interested in DDF-based spectroscopy and imaging.

<p>This dissertation focuses on a very special topic in the field of Nuclear Magnetic Resonance (NMR) in solution: Intermolecular Multiple Quantum Coherences, or iMQCs, which can only be created by intermolecular dipolar couplings. Since the very beginnings of NMR, it has been known that dipolar couplings dominate the solid-state linewidth for spin-1/2 nuclei, but the effects are still not fully understood. The angular dependency (1-3cos2&#952;ij) and distant dependency (rij-3) of dipolar coupling led to an oversimplified conclusion that it can be ignored in an isotropic liquid. Thus, it was surprising when COSY Revamped by Asymmetric Z-gradient Echo Detection (CRAZED) was first introduced in the early `90s and showed strong iMQC signals. Since then, CRAZED has inspired a wide range of applications for iMQCs and led to two different but equivalent mathematical frameworks to describes these effects, which we call the conventional DDF theory.</p><p>However, several disagreements between the conventional DDF theory and experiments have grasped our attention recently. This dissertation will: first, demonstrate how conventional picture fails by two examples, Multi-axis CRAZED (MAXCRAZED) and Gradient-embedded COSY Experiment (GRACE); second, provide a corrected DDF theory; and, third, discuss what impact this correction will bring.</p><p>Intermolecular double quantum coherences (iDQCs) are very sensitive to the local anisotropy (10&#956;m - 1mm) and can be used to create positive contrast highlighting superparamagnetic iron oxide nanoparticles (SPIONs). This dissertation will show the design and optimization of iDQC anisotropy by a series of phantom experiments. A set of numerical simulations will then be provided for a sub-voxel level explanation. We will also demonstrate how the newly corrected DDF theory can be quickly adapted to improve the iDQC anisotropy.</p><p>Finally, as a side product of this research, the mechanism of diacetyl hydration/dehydration as solved by NMR will be provided.</p> / Dissertation