  Objective: Multi-shot interleaved echo planer imaging can obtain
diffusion-weighted images (DWI) with high spatial resolution and low
distortion, but suffers from ghost artifacts introduced by phase variations
between shots. In this work, we aim at solving the challenging reconstructions
under inter-shot motions between shots and a low signal-to-noise ratio.
Methods: An explicit phase model with paired phase and magnitude priors is
proposed to regularize the reconstruction (PAIR). The former prior is derived
from the smoothness of the shot phase and enforced with low-rankness in the
k-space domain. The latter explores similar edges among multi-b-value and
multi-direction DWI with weighted total variation in the image domain. Results:
Extensive simulation and in vivo results show that PAIR can remove ghost
artifacts very well under a high number of shots (8 shots) and significantly
suppress the noise under the ultra-high b-value (4000 s/mm2). Conclusion: The
explicit phase model PAIR with complementary priors has a good performance on
challenging reconstructions under inter-shot motions between shots and a low
signal-to-noise ratio. Significance: PAIR has great potential in advanced
clinical DWI applications and brain function research.
