Fig. 1.

Single-shot EPI images may greatly suffer from geometric distortions, as shown in (a), a problem that can be very much alleviated using k-space segmentation, as shown in (b). The acquisition in (b) was made over 4 TR intervals as opposed to a single TR interval in (a), and these 4-shot data were reconstructed as described in Ref. (1). The main goal of the present work was to accelerate multi-shot imaging, to make it essentially as fast as single-shot imaging while preserving the geometric-fidelity advantages seen here. (The single-shot image in (a) was acquired using 80 echoes, 62.5% partial-Fourier, echo spacing = 668 μs, matrix size = 128×128, FOV = 25.6 cm, TR = 3 s, 4 mm slice, b ≈ 0 s/mm². The four-shot image in (b) involved the same parameters as above, except for 32 echoes per echo train, no partial-Fourier and echo spacing = 664 μs).