3D‐EPI blip‐up/down acquisition (BUDA) with CAIPI and joint Hankel structured low‐rank reconstruction for rapid distortion‐free high‐resolution T2* mapping

Abstract

This work aims to develop a novel distortion-free 3D-EPI acquisition and image reconstruction technique for fast and robust, high-resolution, whole-brain imaging as well as quantitative T * 2 mapping. Methods: 3D Blip-up and -down acquisition (3D-BUDA) sequence is designed for both single-and multi-echo 3D gradient recalled echo (GRE)-EPI imaging using multiple shots with blip-up and -down readouts to encode B 0 field map information. Complementary k-space coverage is achieved using controlled aliasing in parallel imaging (CAIPI) sampling across the shots. For image reconstruction, an iterative hard-thresholding algorithm is employed to minimize the cost function that combines field map information informed parallel imaging with the structured low-rank constraint for multi-shot 3D-BUDA data.

Three‐dimensional echo‐shifted EPI with simultaneous blip‐up and blip‐down acquisitions for correcting geometric distortion

“…We have demonstrated a technique -esEPI-BUDA in which two interleaved k-space datasets with reversed k-space trajectories can be acquired in a single shot. Compared to traditional BUDA techniques for image distortion correction, [15][16][17][18][19]31 esEPI-BUDA offers a major advantage by improving the acquisition efficiency. With concurrent blip-up and blip-down acquisitions in a single shot, esEPI-BUDA can also be more resilient to motion and allow B 0 -field maps to be estimated dynamically throughout a time series.…”

“…As an attractive technique for distortion correction in EPI, BUDA has been successfully applied to susceptibility-weighted imaging, diffusion-weighted imaging, and T 2 mapping. [15][16][17][18][19]31 Extension to fMRI has been challenging as the acquisitions of blip-up and blip-down data in two separated TRs lead to a substantially…”

“…This allows the two k-space datasets be effectively used in the Hankel structured low-rank image reconstruction. [15][16][17][18][19] In principle, the esEPI-BUDA pulse sequence described above can be used for 2D or 3D imaging. In the former case, the slab-selection gradient along the G z -axis is reduced to a slice-selection gradient, while in the latter case, a conventional stepping phase-encoding gradient is applied along the G z -axis, providing spatial localization for both echo trains as shown in Figure 1A.…”

“…13,14 This issue has been elegantly addressed using a technique known as BUDA (blip-up/down acquisition). [15][16][17][18][19] BUDA is based on a forward model that links the distortion-free image to the corrupted raw k-space data. This allows distortion-corrected images to be reconstructed from the k-space data acquired with blip-up and blip-down phase-encoding gradients by solving the corresponding inverse problem with Hankel structured low-rank constraint.…”

“…This allows distortion-corrected images to be reconstructed from the k-space data acquired with blip-up and blip-down phase-encoding gradients by solving the corresponding inverse problem with Hankel structured low-rank constraint. In previous studies, [15][16][17][18][19] BUDA has been successfully applied to susceptibility-, diffusion-, and relaxation-weighted imaging and demonstrated its robustness in geometric distortion correction for 2D and 3D EPI.…”