CEST IMAGING OF GLYCOGEN CONTENT COMPARED TO IN VIVO GLYCOGENOLYSIS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。最近，我们提出了一种通过糖原的氢氧根质子与水质子相互作用的磁共振成像糖原的方法，而水质子可以通过磁化转移来测量。简单地说，糖原分子中的交换质子（OH）可以用正确的质子核磁共振频率选择性地照射。由于与水质子的快速化学交换，这种自旋标签可以通过水线检测到，因此可以通过传统的MRI实验检测到。与其他磁化转移实验一样，关键是比较糖原OH质子辐照下的体积水信号与相反频率下的体积水信号的水共振。糖原中氢氧根质子的交换可以通过这两个频率辐照得到的归一化水信号强度之间的显著差异来检测。更复杂的方法也是可行的。例如，可以得到一个完整的z谱，而不是使用两个频率中的最小值。z谱的不对称性可归因于可交换OH基团。我们在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，我们希望整合该RR中可用的2H NMR方法，以便我们可以在巴尔的摩的磁体中测量患者的糖原溶解，将样品运送到达拉斯，并通过CEST比较人类肝糖原溶解率和氘的肝糖原溶解率。

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.