Advantages of short repetition time resting-state functional MRI enabled by simultaneous multi-slice imaging

Abstract

BACKGROUND\nRecent advancements in simultaneous multi-slice (SMS) imaging techniques have enabled whole-brain resting-state fMRI (rs-fMRI) scanning at sub-second temporal resolution, providing spectral ranges much wider than the typically used range of 0.01-0.1\u2009Hz. However, the advantages of this accelerated acquisition for rs-fMRI have not been evaluated.\n\n\nNEW METHOD\nIn this study, we used SMS Echo Planar Imaging (EPI) to probe whole-brain functional connectivity with a short repetition time (TR\u2009=\u2009350\u2009ms) and compared it with standard EPI with a longer TR of 2000\u2009ms. We determined the effect of scan length and investigated the temporal filtration strategies that optimize results based on metrics of signal-noise separation and test-retest reliability using both seed-based and independent component analysis (ICA).\n\n\nRESULTS\nWe found that use of either the entire frequency range of 0.01-1.4\u2009Hz or the entire frequency range with the exclusion of typical cardiac and respiratory frequency values tended to provide the best functional connectivity maps.\n\n\nCOMPARISON WITH EXISTING METHODS\nWe found that the SMS-acquired rs-fMRI scans had improved the signal-noise separation, while preserving the same level of test-retest reliability compared to conventional EPI, and enabled the detection of reliable functional connectivity networks with scan times as short as 3\u2009min.\n\n\nCONCLUSIONS\nOur findings suggest that whole-brain rs-fMRI studies may benefit from the increased temporal resolution enabled by the SMS-EPI acquisition, leading to drastic scan time reductions, which in turn should enable the more widespread use of rs-fMRI in clinical research protocols.