High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
Molecular Imaging Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy.
NMR Biomed. 2019 Sep;32(9):e4113. doi: 10.1002/nbm.4113. Epub 2019 Jul 17.
To determine individual glucose hydroxyl exchange rates at physiological conditions and use this information for numerical optimization of glucoCEST/CESL preparation. To give guidelines for in vivo glucoCEST/CESL measurement parameters at clinical and ultra-high field strengths.
Five glucose solution samples at different pH values were measured at 14.1 T at various B power levels. Multi-B -Z-spectra Bloch-McConnell fits at physiological pH were further improved by the fitting of Z-spectra of five pH values simultaneously. The obtained exchange rates were used in a six-pool Bloch-McConnell simulation including a tissue-like water pool and semi-solid MT pool with different CEST and CESL presaturation pulse trains. In vivo glucose injection experiments were performed in a tumor mouse model at 7 T.
Glucose Z-spectra could be fitted with four exchanging pools at 0.66, 1.28, 2.08 and 2.88 ppm. Corresponding hydroxyl exchange rates could be determined at pH = 7.2, T = 37°C and 1X PBS. Simulation of saturation transfer for this glucose system in a gray matter-like and a tumor-like system revealed optimal pulses at different field strengths of 9.4, 7 and 3 T. Different existing sequences and approaches are simulated and discussed. The optima found could be experimentally verified in an animal model at 7 T.
For the determined fast exchange regime, presaturation pulses in the spin-lock regime (long recover time, short yet strong saturation) were found to be optimal. This study gives an estimation for optimization of the glucoCEST signal in vivo on the basis of glucose exchange rate at physiological conditions.
在生理条件下确定单个葡萄糖羟基交换率，并将此信息用于 glucoCEST/CESL 制备的数值优化。为临床和超高场强下的体内 glucoCEST/CESL 测量参数提供指导。
在 14.1 T 下，在不同的 B 功率水平下测量了五个不同 pH 值的葡萄糖溶液样品。在生理 pH 下，通过同时拟合五个 pH 值的 Z 谱，进一步改进了多 B -Z 谱 Bloch-McConnell 拟合。所得交换率用于包括组织样水池和半固体 MT 池的六个池 Bloch-McConnell 模拟，其中包含不同的 CEST 和 CESL 预饱和脉冲序列。在 7 T 的肿瘤小鼠模型中进行了体内葡萄糖注射实验。
葡萄糖 Z 谱可以用四个交换池在 0.66、1.28、2.08 和 2.88 ppm 处拟合。在 pH = 7.2、T = 37°C 和 1X PBS 下，可以确定相应的羟基交换率。在灰质样和肿瘤样系统中对该葡萄糖系统的饱和传递进行模拟表明，在 9.4、7 和 3 T 的不同场强下有最佳脉冲。模拟并讨论了不同现有的序列和方法。在 7 T 的动物模型中可以验证所发现的最佳条件。
对于确定的快速交换体系，在自旋锁定体系（长恢复时间，短而强的饱和）中的预饱和脉冲被发现是最佳的。本研究基于生理条件下的葡萄糖交换率，对体内 glucoCEST 信号的优化提供了估计。
