Improving the spatial resolution of magnetic resonance inverse imaging via the blipped-CAIPI acquisition scheme

摘要

Using simultaneous acquisition from multiple channels of a radio-frequency (RF) coil array, magnetic resonance inverse imaging (Inl) achieves functional MRI acquisitions at a rate of 100 ms per whole-brain volume. Inl 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 Inl 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-Inl (blnl) method can increase the average spatial resolution by 15.1% (1.3 mm) across the whole brain and from 32.6% (4.2 mm) in subcortical regions, as compared to the Inl method. In a visual fMRI experiment, we demonstrate that, compared to Inl, the spatial distribution of blnl 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, blnl can be a useful fMRI tool for obtaining high spatiotemporal information for clinical and cognitive neuroscience studies.