Simultaneous multislice accelerated interleaved EPI DWI using generalized blipped-CAIPI acquisition and 3D K-space reconstruction

Purpose: Simultaneous multislice (SMS) has been proved to be powerful for accelerating single-shot echo-planar imaging (ssh-EPI) based diffusion-weighted imaging (DWI), but there are some obstacles for applying SMS to interleaved echo-planar imaging (iEPI) DWI. The primary challenge is to effectively combine slice unfolding for SMS and intershot phase correction for multishot DWI. In this study, a novel acquisition and reconstruction method for SMS-accelerated high-resolution iEPI DWI is proposed.

Theory and methods: The traditional blipped-controlled aliasing in parallel imaging (blipped-CAIPI) for ssh-EPI is generalized for iEPI acquisitions. An SMS three-dimensional (3D) navigator acquisition is designed to record the intershot phase variations. Then, slice unfolding and intershot phase correction are performed simultaneously in an SMS 3D k-space. The performance of the proposed method is demonstrated in both four-shot and eight-shot iEPI DWI and compared with ssh-EPI and unaccelerated iEPI DWI.

Results: The proposed method successfully unfolded the simultaneously excited slices and effectively suppressed artifacts from intershot phase variations. The SMS-accelerated iEPI improved the imaging efficiency, while preserving comparable image quality as unaccelerated iEPI DWI.

Conclusions: The proposed acquisition and reconstruction is an effective method for accelerating multishot high-resolution DWI, which may be valuable for both neuroscience research and clinical diagnosis. Magn Reson Med 77:1593-1605, 2017. © 2016 International Society for Magnetic Resonance in Medicine.