The Structural Dependence of CRAZED Imaging

描述（由申请人提供）：

DESCRIPTION (provided by applicant): The overall aims of this proposal are to further develop and understand the information obtainable from a novel MR imaging technique based on the creation of intermolecular multiple quantum coherences (IMQC) in water in tissues, and to evaluate the potential of this new imaging technique and contrast mechanism for characterizing tissue structure. IMQC imaging was first demonstrated only six years ago, and it provides information on material properties that are conceptually different and potentially more valuable compared to conventional MR imaging methods. However, despite the widespread interest in using this new approach as a contrast mechanism in imaging, little work has been performed to demonstrate how IMQC signals depend on tissue properties of biological interest. We therefore aim to elucidate the signal dependence in IMQC-MRI on tissue structure, relaxation times, diffusion, chemical shift heterogeneity, and pulse sequence timings. Specifically, we will investigate the dependence of the CRAZED (COSY revamped with asymmetric z gradient echo detection) imaging sequence on sample structure, and how this dependence is influenced by the sample characteristics and pulse sequence parameters. Previous work has demonstrated that the CRAZED signal can be tuned to be sensitive only to those spins that are separated by a specific dimension that is determined by the nature of a field gradient imposed by the experiment. Such a dependence offers a unique user-controllable contrast mechanism. However, recent results have called into question the existence of this structural sensitivity at in vivo relaxation times and the dependence on any such effect on the pulse sequence timings. We aim to clarify the factors that affect this dependence.