With the successful application of deep learning in magnetic resonance imaging, parallel imaging techniques based on neural networks have attracted wide attentions. However, without high-quality fully sampled datasets for training, the performance of these methods tends to be limited. To address this issue, this paper proposes a physics based unsupervised contrastive representation learning (PARCEL) method to speed up parallel MR imaging. Specifically, PARCEL has three key ingredients to achieve direct deep learning from the undersampled k-space data. Namely, a parallel framework has been developed by learning two branches of model-based networks unrolled with the conjugate gradient algorithm; Augmented undersampled k-space data randomly drawn from the obtained k-space data are used to help the parallel network to capture the detailed information. A specially designed co-training loss is designed to guide the two networks to capture the inherent features and representations of the-to-be-reconstructed MR image. The proposed method has been evaluated on in vivo datasets and compared to five state-of-the-art methods, whose results show PARCEL is able to learn useful representations for more accurate MR reconstructions without the reliance on the fully-sampled datasets.

为了解决神经网络模型解释性不足、训练数据有限的问题，本文提出了一种基于物理学的无监督对比表示学习方法(PARCEL)，通过两个网络的对比学习实现MRI图像的高精度重建。结果表明，PARCEL方法能够实现准确的MRI重建而不依赖于全采样数据集。

PARCEL: 多线圈MR成像的基于物理的无监督对比度表示学习