Meara Simon J P, Barker Gareth J
Centre for Neuroimaging Sciences, Department of Neurology, Institute of Psychiatry, London, United Kingdom.
Magn Reson Med. 2005 Jul;54(1):241-5. doi: 10.1002/mrm.20541.
The fast spin-echo (FSE) sequence is frequently used as a fast data-readout technique in conjunction with other pulse sequence elements, such as in fluid-attenuated inversion-recovery (FLAIR) and double inversion-recovery (DIR) sequences. In order to implement those pulse sequences, an understanding is required of how the longitudinal magnetization evolves during the FSE part of the sequence. This evolution has been addressed to a certain extent by previous publications, but the DIR literature in particular appears to be replete with approximations to the exact expression for the longitudinal magnetization, and several papers contain errors. Equations are therefore presented here for the evolution of the longitudinal magnetization for a FSE readout. These are then applied to calculate the magnetization available immediately prior to the 90 degrees imaging pulse for the FLAIR-FSE and DIR-FSE pulse sequences.
快速自旋回波（FSE）序列经常作为一种快速数据读出技术，与其他脉冲序列元件结合使用，例如在液体衰减反转恢复（FLAIR）和双反转恢复（DIR）序列中。为了实现这些脉冲序列，需要了解纵向磁化强度在序列的FSE部分期间是如何演变的。以前的出版物已经在一定程度上讨论了这种演变，但特别是DIR文献中似乎充斥着对纵向磁化强度精确表达式的近似，并且几篇论文存在错误。因此，这里给出了FSE读出时纵向磁化强度演变的方程。然后将这些方程应用于计算FLAIR-FSE和DIR-FSE脉冲序列在90度成像脉冲之前立即可用的磁化强度。
