CEST IMAGING OF GLYCOGEN

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 最近，我们提出了一种通过MRI成像糖原的方法，通过糖原的OH质子与水质子的相互作用，可以使用磁化转移测量。简而言之，糖原分子中的可交换质子（OH）可以用正确的质子NMR频率选择性地照射。 由于与水质子的快速化学交换，这种自旋标记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，关键是将糖原的OH质子照射存在下的本体水信号与相对于水共振的相反频率下的本体水信号进行比较。糖原中OH质子的交换可以被检测为通过在这两个频率下照射获得的归一化水信号强度之间的显著差异。更复杂的方法也是可行的。 例如，代替使用两个频率中的最小值，可以获得全Z频谱。 z光谱中的不对称性可归因于可交换的OH基团。 糖原的非侵入性测量是分析体内代谢状态的组成部分。虽然许多研究报告了糖原的检测，但关注其定量的报告有限。此外，7T全身扫描仪的扩展使用需要优化该特定领域的糖原采集协议。我们将研究三种不同的方法，糖原检测和定量在7T：直接13 C MRS，glycocest和直接质子MRS。一个半圆柱体的发射接收表面线圈半径为13厘米，用于所有的研究。线圈在1H和13C的正交运行。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. 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. Noninvasive measurement of glycogen is an integral part of profiling the metabolic state in vivo. While many studies have reported detection of glycogen, there are limited reports that have focused on its quantification. Furthermore, the expanded use of 7T whole body scanners requires optimization of the glycogen acquisition protocols for this particular field. We will investigate three different approaches for glycogen detection and quantification at 7T: direct 13C MRS, glycocest and direct proton MRS. A half-cylinder transmit-receive surface coil with radius of 13-cm was used for all studies. The coil runs in quadrature for both 1H and 13C.