Evaluation of highly accelerated simultaneous multi-slice EPI for fMRI.
Evaluation of highly accelerated simultaneous multi-slice EPI for fMRI.
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DOI：
10.1016/j.neuroimage.2014.10.027
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发表时间：
2015-01-01
期刊：
影响因子：
5.7
通讯作者：
Feinberg DA
中科院分区：
文献类型：
--
作者：
Chen L;T Vu A;Xu J;Moeller S;Ugurbil K;Yacoub E;Feinberg DA
回波平面成像（EPI）是最广泛用于血氧水平依赖（BOLD）功能性MRI（fMRI）的MRI技术。EPI速度的最新进展已经通过同时多切片（SMS）方法实现，该方法将来自多频带（MB）射频脉冲的加速因子M和来自同时图像重聚焦（SIR）的S相结合，以在一个回波序列中采集总共N=S × M个图像，从而在总采集时间上比传统EPI加快N倍。我们使用S和M的不同组合评估了高达N=48的加速度，这允许使用32通道头部线圈在3 T下在短至100 ms的时间内进行全脑成像。通过tSNR以及BOLD对比噪声比（CNR）和来自fMRI实验中的棋盘格和电影片段的信息内容来评估加速度参数的各种组合。我们发现，在低加速因子（N ≤ 6）下，设置S=1并单独改变M在所有评估指标中产生最佳结果，而在加速N=8时，使用S=1和S=2序列的结果混合。在更高的加速因子（N > 8）下，使用S=2产生了最大的BOLD CNR和通过电影剪辑帧的分类测量的信息内容。重要的是，我们发现，与2 s的TR相比，使用300 ms - 600 ms范围内的相对快速TR的BOLD信息内容显着更大，这表明在基于任务的fMRI中，更快的TR在单位时间内捕获更多的信息。
Echo planar imaging (EPI) is the MRI technique that is most widely used for blood oxygen level-dependent (BOLD) functional MRI (fMRI). Recent advances in EPI speed have been made possible with simultaneous multi-slice (SMS) methods which combine acceleration factors M from multiband (MB) radiofrequency pulses and S from simultaneous image refocusing (SIR) to acquire a total of N=S × M images in one echo train, providing up to N times speed-up in total acquisition time over conventional EPI. We evaluated accelerations as high as N=48 using different combinations of S and M which allow for whole brain imaging in as little as 100 ms at 3T with a 32 channel head coil. The various combination of acceleration parameters were evaluated by tSNR as well as BOLD contrast-to-noise ratio (CNR) and information content from checkerboard and movie clips in fMRI experiments. We found that at low acceleration factors (N ≤ 6), setting S=1 and varying M alone yielded the best results in all evaluation metrics, while at acceleration N=8 the results were mixed using both S=1 and S=2 sequences. At higher acceleration factors (N > 8), using S=2 yielded maximal BOLD CNR and information content as measured by classification of movie clip frames. Importantly, we found significantly greater BOLD information content using relatively fast TRs in the range 300 ms - 600 ms compared to a TR of 2 s, suggesting that faster TRs capture more information per unit time in task based fMRI.
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