Fig. 3.

The M-EPI pulse sequence compared with conventional EPI. Top left: EPI pulse sequence generates a single slice image during each readout train, which is repeated for each slice to scan the whole brain. The multiband technique replaces the single slice excitation pulse with multiband (MB) pulses to excite several slices simultaneously, which are then unaliased using array coil sensitivity profiles. As such, far fewer repeats are required to scan the whole brain. Bottom left: Multiplexed-EPI (M-EPI) pulse sequence combines the SIR approach with the MB technique: SIR consecutively excites s slices (s = 3 is shown in the pulse sequence diagram with pulses in red, blue and green) and reads them out in a single echo train, separated in time. Using MB pulses to simultaneously excite m slices instead of exciting each single slice in the SIR approach produces the M-EPI sequence, with a “slice acceleration” of (s × m) leading to (s × m) number of slices collected in a single echo train. Right: Each column shows four (of 60) slices from a whole brain (2 mm isotropic resolution) 3T data set obtained with the M-EPI technique, shown with the (s × m) acceleration factors ranging from 4 to 12.

Adapted with permission from Feinberg et al. (2010).