Evaluation of 2D multiband EPI imaging for high-resolution, whole-brain, task-based fMRI studies at 3T: Sensitivity and slice leakage artifacts.
Evaluation of 2D multiband EPI imaging for high-resolution, whole-brain, task-based fMRI studies at 3T: Sensitivity and slice leakage artifacts.
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DOI：
10.1016/j.neuroimage.2015.08.056
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发表时间：
2016-01-01
期刊：
影响因子：
5.7
通讯作者：
Weiskopf N
中科院分区：
文献类型：
--
作者：
Todd N;Moeller S;Auerbach EJ;Yacoub E;Flandin G;Weiskopf N
需要高分辨率全脑覆盖的功能磁共振成像 (fMRI) 研究需要较长的扫描时间，这主要是由采集的大量薄片驱动的。二维多频带回波平面成像（EPI）序列加速了沿切片方向的数据采集，因此通过提高时间分辨率而不牺牲空间分辨率，代表了此类研究的一种有吸引力的方法。在这项工作中，对 2D 多波段 EPI 序列进行了优化，以在 3 T 下对 10 名健康志愿者进行成像，同时执行视觉和运动任务，以实现 1.5 mm 各向同性全脑采集。序列的性能根据多带 (MB) 因子 1、2、4 和 6 时的 BOLD 灵敏度和假阳性激活，结合 2 × (GRAPPA 2) 的面内 GRAPPA 加速度，以及 Slice-GRAPPA 和 Split Slice-GRAPPA 两种重建方法进行评估。灵敏度结果表明，与 MB 1 相比，MB 2、4 和 6 的时间信噪比 (tSNR) 和 t 分数统计显着增加。最佳灵敏度的 MB 因子根据解剖位置和重建方法而变化。当使用 Slice-GRAPPA 重建时，在 10 名志愿者的 MB 2 × GRAPPA 2、MB 4 × GRAPPA 2 和 MB 6 × GRAPPA 2 各自的加速中，在 1 个实例、35 个实例和 70 个实例中看到了由于同时激发的切片之间的信号泄漏而导致假阳性激活的证据。使用 Split Slice-GRAPPA 重建显着抑制了假阳性的发生率，达到 1 个实例、5 个实例实例，以及相同各自加速因子的 5 个实例。使用 MB 2 × GRAPPA 2 加速因子的成像协议可以自信地用于高分辨率全脑成像，以提高 BOLD 灵敏度，并且由于切片泄漏而导致假阳性激活的可能性非常低。使用更高加速因子（MB 3 或 MB 4 × GRAPPA 2）的成像协议可能会提供更大的灵敏度增益，但应仔细优化，以尽量减少错误激活的可能性。对 MB 因子 1、2、4 和 6 以及两次重建的 fMRI 性能进行了评估。 MB 加速度 2、4 和 6 比 MB 1 改进了 BOLD 灵敏度指标。在高加速度下会出现由于信号泄漏导致的误报激活。使用 Split Slice-GRAPPA 重建可显着减少误报。
Functional magnetic resonance imaging (fMRI) studies that require high-resolution whole-brain coverage have long scan times that are primarily driven by the large number of thin slices acquired. Two-dimensional multiband echo-planar imaging (EPI) sequences accelerate the data acquisition along the slice direction and therefore represent an attractive approach to such studies by improving the temporal resolution without sacrificing spatial resolution. In this work, a 2D multiband EPI sequence was optimized for 1.5 mm isotropic whole-brain acquisitions at 3 T with 10 healthy volunteers imaged while performing simultaneous visual and motor tasks. The performance of the sequence was evaluated in terms of BOLD sensitivity and false-positive activation at multiband (MB) factors of 1, 2, 4, and 6, combined with in-plane GRAPPA acceleration of 2 × (GRAPPA 2), and the two reconstruction approaches of Slice-GRAPPA and Split Slice-GRAPPA. Sensitivity results demonstrate significant gains in temporal signal-to-noise ratio (tSNR) and t-score statistics for MB 2, 4, and 6 compared to MB 1. The MB factor for optimal sensitivity varied depending on anatomical location and reconstruction method. When using Slice-GRAPPA reconstruction, evidence of false-positive activation due to signal leakage between simultaneously excited slices was seen in one instance, 35 instances, and 70 instances over the ten volunteers for the respective accelerations of MB 2 × GRAPPA 2, MB 4 × GRAPPA 2, and MB 6 × GRAPPA 2. The use of Split Slice-GRAPPA reconstruction suppressed the prevalence of false positives significantly, to 1 instance, 5 instances, and 5 instances for the same respective acceleration factors. Imaging protocols using an acceleration factor of MB 2 × GRAPPA 2 can be confidently used for high-resolution whole-brain imaging to improve BOLD sensitivity with very low probability for false-positive activation due to slice leakage. Imaging protocols using higher acceleration factors (MB 3 or MB 4 × GRAPPA 2) can likely provide even greater gains in sensitivity but should be carefully optimized to minimize the possibility of false activations. MB factors 1, 2, 4, and 6 and two reconstructions were evaluated for fMRI performance. MB accelerations 2, 4, and 6 improved BOLD sensitivity metrics over MB 1. False-positive activation due to signal leakage was seen at high accelerations. Use of Split Slice-GRAPPA reconstruction significantly reduces false positives.