An assessment of motion artefacts in multi band EPI for high spatial and temporal resolution resting state fMRI

Purpose: Multiband (MB) echo planar imaging (EPI) is a recent MRI technique capable of acquiring multi-slice, whole brain FMRI data with subsecond temporal resolution. The technique employs MB pulses to simultaneously excite n non-contiguous slices which are then separated by utilizing spatial information in multi-channel receive arrays with parallel imaging reconstruction1-4. MB-EPI thereby acquires n images in each EPI echo train as opposed to the single image acquired by conventional “single-band” EPI, and therefore offers increased temporal and/or spatial resolution. Further, by increasing the temporal degrees-of-freedom, MB-EPI increases the temporal SNR, improving multivariate analyses such as independent component analysis (ICA). However, it is reasonable to expect MB-EPI to exhibit increased motion sensitivity due to the combination of short TR (spin history) and parallel imaging. In this study, the performance of MB-EPI with different acceleration factors was compared to that of standard EPI with respect to sensitivity to subject motion.Methods: 6 healthy volunteers (both MRI naïve and MRI trained) were scanned on a 3T Siemens Verio scanner equipped with a 32-channel receive-only head coil array. Each volunteer was scanned on 4 occasions in order to compare 2mm MB with acceleration factors of 4 and 8 (MB4-2mm and MB8-2mm) with un-accelerated data at 2mm (MB1-2mm) and the “more conventional” 3mm resolution (MB1-3mm, with GRAPPA R= 2)(Table 1). The complete protocol included resting and task conditions, but here we focus on resting-state data. All sequences used partial Fourier= 7/8 and flip angle …