Lineshape And Rotating-frame Longitudinal Relaxation Of Intermolecular Multiple-Quantum Coherences, And Its MRI Applications

Intermolecular multiple-quantum coherence (iMQC) phenomenon is a hot topic in the NMR field and has ever arose great controversy in the theoretical formalism of iMQCs. The results in this thesis can be regarded as an extension and supplement of iMQC theory and its applications, which are summarized as follows:1. A full theoretical formalism about the lineshape of iMQC spectra was proposed for the first time. The theory can be used to well explain the characteristics of iMQC spectra, such as lineshape, peak height, linewidth, and phase. Since there are many similar features between iMQC signals and radiation-damping ones, both of which commonly exist in the high-polarized NMR spin systems, a detailed comparison was performed between them in different aspects. Form the viewpoint of lineshape, the results showed that they are two grossly different physical mechanisms.2. The spin-locking technique was incorporated into the evolution period of CRAZED pulse sequence. A novel concept of"rotating-frame intermolecular double-quantum longitudinal relaxation"was defined and quantitatively characterized by the classical dipolar-field theory. The spectroscopic measurement of the relaxation provided the MRI researchers a good guide in its MRI applications of relaxation weighting.3. A series of MR images, which are formed by standard spin-echo imaging method and weighted by rotating-frame intermolecular double-quantum longitudinal relaxation T1ρ,DQ, were obtained when using on-resonance spin-locking pulse. The merits and shortcomings of this imaging method were presented in detail. The results...