Double Asymmetric Spin Echo EPI ( dASE ‐ EPI ) Enables fMRI of the Entire Rat Brain at 9.4 T

Purpose Development and evaluation of a double asymmetric spin echo planar imaging ( dASE ‐ EPI ) sequence to balance sensitivity to blood oxygenation level‐dependent ( BOLD ) contrast with mitigation of susceptibility‐induced intravoxel spin dephasing in ultra high‐field rodent brain imaging. Methods A dASE ‐ EPI pulse sequence was implemented and resting‐state BOLD fMRI was acquired in the rat brain. Data acquired with dASE ‐ EPI were compared to conventional gradient‐recalled EPI . Functional connectivity analyses were performed to assess detection of established networks and to evaluate signal recovery in regions affected by susceptibility (e.g., amygdala, hypothalamic nuclei). Results dASE ‐ EPI was found to provide BOLD sensitivity that was non‐inferior to conventional GRE ‐ EPI while substantially reducing susceptibility‐related signal loss. Established functional networks including the bilateral insular, bilateral sensory, and default mode network were reliably detected with dASE ‐ EPI . Functional connectivity of the amygdala, which was obscured in GRE ‐ EPI , was recoverable with the proposed sequence. Conclusion The proposed dASE ‐ EPI pulse sequence is a viable solution when studying brain regions which suffer from severe susceptibility artifacts.