Department of Engineering Science, Institute of Biomedical Engineering, University of Oxford, UK; Department of Engineering Science, Institute of Biomedical Engineering, Centre for Doctoral Training in Healthcare Innovation, University of Oxford, UK.
Magn Reson Med. 2013 Nov;70(5):1251-62. doi: 10.1002/mrm.24567. Epub 2013 Jan 11.
The sampling schedule for chemical exchange saturation transfer imaging is normally uniformly distributed across the saturation frequency offsets. When this kind of evenly distributed sampling schedule is used to quantify the chemical exchange saturation transfer effect using model-based analysis, some of the collected data are minimally informative to the parameters of interest. For example, changes in labile proton exchange rate and concentration mainly affect the magnetization near the resonance frequency of the labile pool. In this study, an optimal sampling schedule was designed for a more accurate quantification of amine proton exchange rate and concentration, and water center frequency shift based on an algorithm previously applied to magnetization transfer and arterial spin labeling. The resulting optimal sampling schedule samples repeatedly around the resonance frequency of the amine pool and also near to the water resonance to maximize the information present within the data for quantitative model-based analysis. Simulation and experimental results on tissue-like phantoms showed that greater accuracy and precision (>30% and >46%, respectively, for some cases) were achieved in the parameters of interest when using optimal sampling schedule compared with evenly distributed sampling schedule. Hence, the proposed optimal sampling schedule could replace evenly distributed sampling schedule in chemical exchange saturation transfer imaging to improve the quantification of the chemical exchange saturation transfer effect and parameter estimation.
化学交换饱和传递成像的采样方案通常在饱和频率偏移上均匀分布。当使用基于模型的分析方法使用这种均匀分布的采样方案来量化化学交换饱和传递效应时，一些采集的数据对于感兴趣的参数的信息量最小。例如，易变质子交换率和浓度的变化主要影响易变池的共振频率附近的磁化。在这项研究中，设计了一种最优的采样方案，以便更准确地量化基于以前应用于磁化转移和动脉自旋标记的算法的胺质子交换率和浓度以及水中心频率偏移。所得到的最优采样方案在胺池的共振频率周围以及在水共振附近重复采样，以最大化数据中用于定量基于模型的分析的信息。在类似组织的体模上的模拟和实验结果表明，与均匀分布的采样方案相比，使用最优采样方案可以在感兴趣的参数中实现更高的精度和精度（某些情况下分别大于 30%和 46%）。因此，所提出的最优采样方案可以替代化学交换饱和传递成像中的均匀分布采样方案，以提高化学交换饱和传递效应的量化和参数估计。
