Chang Wei-Tang, Setsompop Kawin, Ahveninen Jyrki, Belliveau John W, Witzel Thomas, Lin Fa-Hsuan
Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital/Harvard Medical School, Charlestown, MA, USA; Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan.
Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital/Harvard Medical School, Charlestown, MA, USA.
Neuroimage. 2014 May 1;91:401-11. doi: 10.1016/j.neuroimage.2013.12.037. Epub 2013 Dec 27.
Using simultaneous acquisition from multiple channels of a radio-frequency (RF) coil array, magnetic resonance inverse imaging (InI) achieves functional MRI acquisitions at a rate of 100ms per whole-brain volume. InI accelerates the scan by leaving out partition encoding steps and reconstructs images by solving under-determined inverse problems using RF coil sensitivity information. Hence, the correlated spatial information available in the coil array causes spatial blurring in the InI reconstruction. Here, we propose a method that employs gradient blips in the partition encoding direction during the acquisition to provide extra spatial encoding in order to better differentiate signals from different partitions. According to our simulations, this blipped-InI (bInI) method can increase the average spatial resolution by 15.1% (1.3mm) across the whole brain and from 32.6% (4.2mm) in subcortical regions, as compared to the InI method. In a visual fMRI experiment, we demonstrate that, compared to InI, the spatial distribution of bInI BOLD response is more consistent with that of a conventional echo-planar imaging (EPI) at the level of individual subjects. With the improved spatial resolution, especially in subcortical regions, bInI can be a useful fMRI tool for obtaining high spatiotemporal information for clinical and cognitive neuroscience studies.
磁共振逆成像（InI）通过同时采集来自射频（RF）线圈阵列多个通道的数据，以每全脑体积100毫秒的速率实现功能磁共振成像采集。InI通过省略分区编码步骤来加速扫描，并利用RF线圈灵敏度信息求解欠定逆问题来重建图像。因此，线圈阵列中可用的相关空间信息会导致InI重建中的空间模糊。在此，我们提出一种方法，在采集过程中在分区编码方向上采用梯度尖峰，以提供额外的空间编码，以便更好地区分来自不同分区的信号。根据我们的模拟，与InI方法相比，这种带尖峰的InI（bInI）方法可使全脑平均空间分辨率提高15.1%（1.3毫米），在皮质下区域提高32.6%（4.2毫米）。在一项视觉功能磁共振成像实验中，我们证明，与InI相比，在个体受试者层面，bInI血氧水平依赖（BOLD）反应的空间分布与传统回波平面成像（EPI）的更一致。随着空间分辨率的提高，尤其是在皮质下区域，bInI可以成为一种有用的功能磁共振成像工具，用于为临床和认知神经科学研究获取高时空信息。
