BOLD fMRI using a modified HASTE sequence.
BOLD fMRI using a modified HASTE sequence.
复制标题
使用修改后的 HASTE 序列的 BOLD fMRI
DOI：
10.1016/j.neuroimage.2009.07.044
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发表时间：
2010-01-01
期刊：
影响因子：
5.7
通讯作者：
Zhou XJ
中科院分区：
文献类型：
--
作者：
Ye Y;Zhuo Y;Xue R;Zhou XJ
十多年来，涡轮自旋回波（TSE）脉冲序列被认为是fMRI研究中回波平面成像（EPI）序列的替代方案。并行成像的最新发展重新燃起了开发更强大的TSE序列用于fMRI的兴趣。在本研究中，开发了一种改进的半傅立叶采集单次TSE （mHASTE）序列，该序列具有三倍的GRAPPA，以提高时间分辨率，并增加准备时间以提高BOLD灵敏度。采用经典的闪烁棋盘格块设计，系统分析了该方法的BOLD信号特征作为多个序列参数的函数，并与梯度回波和自旋回波EPI序列进行了比较。对5名志愿者视觉皮层的实验研究提供了证据，表明mHASTE对微血管网络周围的血管外BOLD效应更敏感，从而导致更准确的功能定位。研究还表明，mHASTE的激活簇大小随着射频翻转角度和TE的增加而增加，而随着采样k空间中心的回波数（ncenter）的增加而减小。与自旋回波EPI相比，mHASTE的激活簇大小减少了约50%，BOLD对比度减少了约20%。然而，当扫描时间保持不变时，与EPI序列相比，在mHASTE中观察到更高的信噪比和空间上更均匀的时间稳定性。随着进一步的改进和优化，在传统EPI序列有限或禁止的情况下，mHASTE可以成为fMRI的可行替代方案。
For more than a decade, turbo spin echo (TSE) pulse sequences have been suggested as an alternative to echo planar imaging (EPI) sequences for fMRI studies. Recent development in parallel imaging has renewed the interest in developing more robust TSE sequences for fMRI. In this study, a modified half Fourier acquisition single-shot TSE (mHASTE) sequence has been developed with a three-fold GRAPPA to improve temporal resolution as well as a preparation time to enhance BOLD sensitivity. Using a classical flashing checkerboard block design, the BOLD signal characteristics of this novel method have been systematically analyzed as a function of several sequence parameters and compared to those of gradient-echo and spin-echo EPI sequences. Experimental studies on visual cortex of five volunteers have provided evidence suggesting that mHASTE can be more sensitive to extra-vascular BOLD effects around microvascular networks, which leads to more accurate function localization. The studies also show that the activation cluster size in mHASTE increases with the refocusing RF flip angle and TE while decreasing with the echo number (ncenter) used to sample the k-space center. Compared to spin-echo EPI, mHASTE incurs a ~50% reduction in activation cluster size and a ~20% decrease in BOLD contrast. However a higher signal-to-noise ratio and a spatially more uniform temporal stability have been observed in mHASTE as compared to the EPI sequences when the scan times are held constant. With further refinement and optimization, mHASTE can become a viable alternative for fMRI in situations where the conventional EPI sequences are limited or prohibitive.