Fig. 1.

3DEPI sequence diagram with integrated reversed-PE scans. The acquisition is comprised of dummy scans, followed by the acquisition of a fully sampled reference volume (used for estimating coil sensitivities), a single reversed-PE volume, and finally the fMRI acquisition which has the blip gradient polarity restored and matching that of the reference data (a). A single TR from each of these blocks is depicted in (b). These are repeated for each location in the second (slab-selective) phase-encoded direction (denoted “partition” in the Fig.). The fully sampled reference data are acquired with 8 in-plane segments to match the distortions of the fMRI times series, which have 4-fold acceleration and 2-fold segmentation. The colour indicates the temporal order, which is shifted in time so that the k-space centre would always be traversed at the same point in the T2* decay curve. Similar time shifting is applied for the 2-fold segmented under-sampled data. Note that the MT-3DEPI acquisition is achieved by inserting a module consisting of an off-resonance pre-pulse and spoiler gradient to impart MT weighting, using a 1-1 binomial excitation and increasing the coverage in the slab-selective direction (see Table 1 for full details).