Quantitative magnetization transfer imaging using balanced SSFP
Quantitative magnetization transfer imaging using balanced SSFP
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DOI：
10.1002/mrm.21705
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发表时间：
2008-09-01
影响因子：
3.3
通讯作者：
Bieri, O.
中科院分区：
文献类型：
--
作者：
Gloor, M.;Scheffler, K.;Bieri, O.
一般认为，平衡稳态自由进动(BSSFP)中的信号形成只是弛豫时间和翻转角的简单函数。对于流体，这一点可以得到证实，但对于更复杂的物质，磁化转移(MT)可能会导致相当大的稳态信号损失。因此，特别是在组织中，对bSSFP的分析描述需要进行修订，以充分考虑到观察到的影响。在这项工作的第一部分，我们在二元自旋浴模型的基础上导出了一个扩展的bSSFP信号方程。基于这种新的bSSFP信号形成模型，可以探索定量的MT参数，如分数池大小、相应的磁化交换率和驰豫时间。在这项工作的第二部分，推导了正常人脑的模型参数。讨论了可能影响模型质量的因素，如B、场不均匀或非共振。总体而言，从双池bSSFP得到的参数与常见的定量MT模型之间有很好的一致性。短的重复时间和高信噪比使bSSFP成为在临床可行的采集时间内获取高分辨率各向同性定量MT图的理想候选者，就像对人脑一样。
It is generally accepted that signal formation in balanced steady-state free precession (bSSFP) is a simple function of relaxation times and flip angle only. This can be confirmed for fluids, but for more complex substances, magnetization transfer (MT) can lead to a considerable loss of steady-state signal. Thus, especially in tissues, the analytical description of bSSFP requires a revision to fully take observed effects into account. In the first part of this work, an extended bSSFP signal equation is derived based on a binary spin-bath model. Based on this new model of bSSFP signal formation, quantitative MT parameters such as the fractional pool size, corresponding magnetization exchange rates, and relaxation times can be explored. In the second part of this work, model parameters are derived in normal appearing human brain. Factors that may influence the quality of the model, such as B, field inhomogeneities or off-resonances, are discussed. Overall, good correspondence between parameters derived from two-pool bSSFP and common quantitative MT models is observed. Short repetition times in combination with high signal-to-noise ratios make bSSFP an ideal candidate for the acquisition of high resolution isotropic quantitative MT maps, as for the human brain, within clinically feasible acquisition times.