【作者】 郑炳文；

【导师】 陈忠；

【作者基本信息】 厦门大学 ， 凝聚态物理， 2005， 博士

【摘要】 分子间多量子相干(Intermolecular Multiple Quantum Coherence,iMQC)是核磁共振领域的前沿热点话题之一,对其的理论解释曾引起广泛争议。本文的工作是对iMQC理论的扩展和补充,主要成果如下:一、首次建立了iMQC信号的线形理论。该理论很好地阐述了iMQC谱在线形、峰强、线宽、相位等方面的特点。由于iMQC和辐射阻尼均存在于高极化核自旋体系中,因此它们在信号特征上有很多相似之处。本文从线形角度对二者进行了详细比较,说明了它们是由不同的物理机理引起的。二、首次将自旋锁定技术引入到CRAZED实验的演化期,提出了“旋转坐标系分子间双量子纵向弛豫”的概念。利用偶极场理论对该弛豫进行了表述,并对该弛豫进行了谱学定量测量,为其在弛豫成像的应用奠定了理论和实验基础。三、提出了在共振自旋锁定条件下得到的旋转坐标系分子间双量子纵向弛豫T1ρ,DQ作为对比度加权参数,采用标准自旋回波成像序列得到一系列磁共振图像,并详细阐述了该方法的优缺点,表明了该弛豫加权成像的独特性和可行性。四、采用偏共振自旋锁定场和快速自旋回波成像得到T1eρf f,DQ弛豫加权成像。此方法提供了两个有效参数可以调节弛豫时间,从而有效控制图像对比度。结果分析表明,该对比度与传统分子间双量子横向弛豫加权完全不同,也区别于共振条件下的T1ρ,DQ加权成像。偏共振方法合成一个有效自旋锁定场,降低了射频场强度,有助于减少临床应用中人体组织对电磁波的吸收。更多还原

【Abstract】 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更多还原