Department of Biomedical Engineering, ND2, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA,
MAGMA. 2013 Oct;26(5):443-50. doi: 10.1007/s10334-012-0364-1. Epub 2013 Jan 26.
Dual-echo fast spin-echo (FSE) sequences are used in T2 relaxometry studies of neurological disorders because of shorter clinical scanning times and protocol simplicity. However, FSE sequences have possible spatial frequency-dependent effects, and derived T2 values may include errors that depend on the spatial frequency characteristics of the brain region of interest.
Dual-echo FSE and multi-echo spin-echo (MESE) sequences were acquired in nine subjects. The T2 decay curves for FSE and MESE sequences were estimated and percent error maps were generated. T2 error values were obtained along each patient's corticospinal tract (CST). Whole-brain white matter (WM) and gray matter (GM) T2 error values were also obtained. The paired t test was performed to evaluate differences in T2 values in the CST between FSE and MESE sequences.
Histograms of error values in CST and in whole-brain WM and GM structures revealed systematic errors in FSE sequences. Significant differences (P < 0.001) in CST T2 values were also observed between FSE and MESE sequences.
Our findings indicate that T2 values derived from FSE sequences are prone to large errors, even in low spatial frequency regions such as the CST, when compared to MESE sequences. Future studies should be aware of this limitation of FSE sequences.
双回波快速自旋回波（FSE）序列由于临床扫描时间较短且协议简单，因此在神经病变的 T2 弛豫研究中被广泛应用。然而，FSE 序列可能存在空间频率依赖性影响，并且衍生的 T2 值可能包含取决于感兴趣脑区的空间频率特征的误差。
在 9 名受试者中采集了双回波 FSE 和多回波自旋回波（MESE）序列。分别对 FSE 和 MESE 序列的 T2 衰减曲线进行了估计，并生成了百分误差图。沿每位患者的皮质脊髓束（CST）获取 T2 误差值。还获得了整个大脑白质（WM）和灰质（GM）的 T2 误差值。采用配对 t 检验评估 FSE 和 MESE 序列之间 CST 中 T2 值的差异。
CST 以及整个大脑 WM 和 GM 结构的误差值直方图显示 FSE 序列存在系统误差。还观察到 FSE 和 MESE 序列之间 CST 的 T2 值存在显著差异（P < 0.001）。
我们的研究结果表明，与 MESE 序列相比，即使在 CST 等低空间频率区域，FSE 序列得出的 T2 值也容易出现较大误差。未来的研究应注意 FSE 序列的这一局限性。
