CEST IMAGING OF GLYCOGEN CONTENT COMPARED TO IN VIVO GLYCOGENOLYSIS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 最近，我们提出了一种通过糖原的OH质子与水质子相互作用来进行核磁共振成像的方法，这种相互作用可以通过磁化转移来测量。简而言之，糖原分子中的可交换质子(OH)可以用正确的质子核磁共振频率选择性地辐射。由于与水质子的快速化学交换，这种自旋标记可以通过水线检测，因此可以通过常规的磁共振实验进行检测。与其他磁化传递实验一样，关键是比较在糖原的OH质子照射下的体水信号和相对于水共振的相反频率的体水信号。在这两个频率照射得到的归一化水信号强度之间的显著差异可以检测到糖原中的OH质子的交换。更复杂的方法也是可行的。例如，可以获得完整的Z谱，而不是使用两个频率中的最小值。Z谱的不对称性可以归因于可交换的OH基团。我们约翰霍普金斯大学的团队有能力在我们的3T系统中独立进行这些研究。然而，我们想要整合这项RR中可用的2H核磁共振方法，这样我们就可以在巴尔的摩的磁铁中测量我们患者的糖原分解，将样本运往达拉斯，并比较CEST测定的人类肝糖原分解率与重离子测定的肝糖原分解率。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Recently we proposed a method for imaging glycogen by MRI through the interaction of the OH protons of glycogen with the water protons which can be measured using magnetization transfer. Briefly, the exchangeable protons (OH) in the glycogen molecule can be selectively irradiated with the correct proton NMR frequency. Because of the fast chemical exchange with water protons, this spin label can be detected through the water line, and hence through the conventional MRI experiment. Like other magnetization transfer experiments, the key is to compare the bulk water signal in the presence of irradiation of the OH protons of glycogen with the bulk water signal at the opposite frequency with respect to the water resonance. The exchange of the OH protons in glycogen can be detected as a significant difference between the normalized water signal intensities obtained by irradiating at these two frequencies. More sophisticated approaches are also feasible. For example, instead of using the minimum of two frequencies, a full Z-spectrum can be obtained. The asymmetry in the z spectrum can be attributed to exchangeable OH groups. Our group at Johns Hopkins has the capability of performing these studies independently in our 3T system. However, we would like to integrate the 2H NMR methods available in this RR so we can measure glycogenolysis in our patients in our magnet in Baltimore, ship the samples to Dallas, and compare liver glycogenolytic rates in humans by CEST to liver glycogenolytic rates by deuterium.