Figure 2.

The schematic at the top left shows the RF pulse train and gradients used in the current implementation of PSF-Choice. The bottom left shows locations in excitation k-space sampled by the α₁₁, α₁₂, α₂₁ and α₂₂ hard pulses over the course of all shots (encodes) as represented by black circles, white diamonds, white circles, and black diamonds respectively. The exact location excited by each hard pulse is governed by the setting of the phase-encoding gradients, Ph_x and Ph_y. The schematic at the top right shows a simple 2D phase-encoding sequence with the same phase-encoding gradients as used for PSF-Choice. The sampled k-space locations are shown at the bottom-right. Note that the 2D phase-encoding k-space sampling increments, Δ^k_x and Δ^k_y, are equal to the sampling increments in excitation k-space, Δ^r_x and Δ^r_y, for the PSF-Choice implementation. The number of encoding steps is also the same for both sequences (= 8x8). However, the area of excitation k-space covered in the PSF-Choice encoding sequence is four times that of k-space covered with the standard phase-encoding sequence.