Mesoscale fMRI at ultra-high spatiotemporal resolutions using 3D Echo Planar TIme- and DYnamic-resolved Imaging (TIDY)

Motivation: Mesoscale fMRI enables investigation of brain's function at cortical layers/columns. Goal(s): To address the major challenges in achieving mesoscale fMRI at <0.5-mm-iso (<0.1-μL): i) high spatial-encoding burden, limiting coverage and spatiotemporal resolutions; ii) severe distortion and T2/T2*-blurring; iii) low SNR. Approach: We introduce a novel acquisition/reconstruction technique, named 3D echo-planar Time- and Dynamic-resolved imaging (TIDY), which leverages multi-dimensional encoding design with time- and dynamic-resolved reconstruction to achieve distortion-free fMRI at ultra-high spatiotemporal resolutions. Results: We achieved distortion-free whole-brain fMRI at 500-um-iso with an 885-ms volume-TR, resulting in robust activation within 4.5-min, and demonstrated fMRI at 340-um-iso with robust visual-pattern activation across cortical layers. Impact: We introduce a novel acquisition/reconstruction technique, named 3D echo planar TIme- and Dynamic-resolved imaging (TIDY), to achieve distortion-free mesoscale fMRI at ultra-high spatiotemporal resolutions (e.g., whole-brain 500-um-iso at 885-ms volume-TR; partial-brain 340-um-iso at 1.2-s volume-TR).