Abstract

To introduce a novel deep learning-based approach for fast and high-quality dynamic multicoil MR reconstruction by learning a complementary time-frequency domain network that exploits spatiotemporal correlations simultaneously from complementary domains. Dynamic parallel MR image reconstruction is formulated as a multivariable minimization problem, where the data are regularized in combined temporal Fourier and spatial (x-f) domain as well as in spatiotemporal image (x-t) domain. An iterative algorithm based on variable splitting technique is derived, which alternates among signal de-aliasing steps in x-f and x-t spaces, a closed-form point-wise data consistency step and a weighted coupling step. The iterative model is embedded into a deep recurrent neural network which learns to recover the image via exploiting spatiotemporal redundancies in complementary domains. Experiments were performed on two datasets of highly undersampled multicoil short-axis cardiac cine MRI scans. Results demonstrate that our proposed method outperforms the current state-of-the-art approaches both quantitatively and qualitatively. The proposed model can also generalize well to data acquired from a different scanner and data with pathologies that were not seen in the training set. The work shows the benefit of reconstructing dynamic parallel MRI in complementary time-frequency domains with deep neural networks. The method can effectively and robustly reconstruct high-quality images from highly undersampled dynamic multicoil data ( and yielding 15 s and 10 s scan times respectively) with fast reconstruction speed (2.8 seconds). This could potentially facilitate achieving fast single-breath-hold clinical 2D cardiac cine imaging.

Highlights

  • Magnetic Resonance Imaging (MRI) is a widely used diagnostic modality which generates images with high spatial and temporal resolution as well as excellent soft tissue contrast

  • Different from our previous work in [41], we propose to model the iterative reconstruction process in x -f domain with the recurrent neural network (CRNN-i [29]) where recurrence is evolving over iterations via hidden-to-hidden connections and the trainable network parameters are shared across sequential iteration steps

  • We have proposed a novel deep learning (DL)-based approach, termed complementary time-frequency domain network (CTFNet), for highly undersampled dynamic parallel MR image reconstruction

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Summary

Introduction

Magnetic Resonance Imaging (MRI) is a widely used diagnostic modality which generates images with high spatial and temporal resolution as well as excellent soft tissue contrast. Parallel imaging (PI) techniques [1,2,3] have been widely used to accelerate MR imaging They speed up the scan time by sampling only a limited number of phase-encoding steps, and exploiting the correlations to restore the missing information in the reconstruction phase. CS-based methods exploit signal sparsity in some specific transform domain, and recover the original image from undersampled k-space data using nonlinear reconstructions. One effective mean to exploit spatio-temporal redundancies for signal recovery in dynamic MRI is to enforce the sparsity in combined spatial and temporal Fourier (x -f ) domain against consistency with the acquired undersampled k-space data, and this can be represented by methods such as k -t FOCUSS [4, 5] and k -t SPARSE-SENSE [6]. The reconstruction speed of these methods is often slow due to the iterative nature of the optimisation used, and in the context of dynamic imaging, the additional time domain further increases the computational demand

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