Zhang Shu, Liu Zheng, Grant Aaron, Keupp Jochen, Lenkinski Robert E, Vinogradov Elena
Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
Division of MR Research, Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
J Magn Reson. 2017 Feb;275:55-67. doi: 10.1016/j.jmr.2016.12.002. Epub 2016 Dec 8.
Chemical exchange saturation transfer (CEST) is a novel contrast mechanism and it is gaining increasing popularity as many promising applications have been proposed and investigated. Fast and quantitative CEST imaging techniques are further needed in order to increase the applicability of CEST for clinical use as well as to derive quantitative physiological and biological information. Steady-state methods for fast CEST imaging have been reported recently. Here, we observe that an extreme case of these methods is a balanced steady-state free precession (bSSFP) sequence. The bSSFP in itself is sensitive to the exchange processes; hence, no additional saturation or preparation is needed for CEST-like data acquisition. The bSSFP experiment can be regarded as observation during saturation, without separate saturation and acquisition modules as used in standard CEST and similar experiments. One of the differences from standard CEST methods is that the bSSFP spectrum is an XY-spectrum not a Z-spectrum. As the first proof-of-principle step, we have implemented the steady-state bSSFP sequence for chemical exchange detection (bSSFPX) and verified its feasibility in phantom studies. These studies have shown that bSSFPX can achieve exchange-mediated contrast comparable to the standard CEST experiment. Therefore, the bSSFPX method has a potential for fast and quantitative CEST data acquisition.
化学交换饱和转移（CEST）是一种新型的对比机制，随着许多有前景的应用被提出和研究，它越来越受到关注。为了提高CEST在临床应用中的适用性以及获取定量的生理和生物学信息，进一步需要快速且定量的CEST成像技术。最近已经报道了用于快速CEST成像的稳态方法。在此，我们观察到这些方法的一个极端情况是平衡稳态自由进动（bSSFP）序列。bSSFP本身对交换过程敏感；因此，在获取类似CEST的数据时无需额外的饱和或准备过程。bSSFP实验可被视为在饱和期间的观察，无需像标准CEST及类似实验那样使用单独的饱和和采集模块。与标准CEST方法的一个区别在于，bSSFP谱是XY谱而非Z谱。作为原理验证的第一步，我们已实现用于化学交换检测的稳态bSSFP序列（bSSFPX），并在体模研究中验证了其可行性。这些研究表明，bSSFPX能够实现与标准CEST实验相当的交换介导对比。因此，bSSFPX方法具有快速且定量获取CEST数据的潜力。
