Compressed sensing is a powerful tool in applications such as magnetic
resonance imaging (MRI). It enables accurate recovery of images from highly
undersampled measurements by exploiting the sparsity of the images or image
patches in a transform domain or dictionary. In this work, we focus on blind
compressed sensing (BCS), where the underlying sparse signal model is a priori
unknown, and propose a framework to simultaneously reconstruct the underlying
image as well as the unknown model from highly undersampled measurements.
Specifically, our model is that the patches of the underlying image(s) are
approximately sparse in a transform domain. We also extend this model to a
union of transforms model that better captures the diversity of features in
natural images. The proposed block coordinate descent type algorithms for blind
compressed sensing are highly efficient, and are guaranteed to converge to at
least the partial global and partial local minimizers of the highly non-convex
BCS problems. Our numerical experiments show that the proposed framework
usually leads to better quality of image reconstructions in MRI compared to
several recent image reconstruction methods. Importantly, the learning of a
union of sparsifying transforms leads to better image reconstructions than a
single adaptive transform.

本研究提出了一种同时重建基础图像和未知模型的盲压缩感知框架，用于利用稀疏变换或字典中图像 / 图像补丁的稀疏性从高度欠采样的测量中精确恢复图像。我们将这个模型扩展到了一个转换融合模型，以更好地捕捉自然图像中的特征。与其他最近的图像重建方法相比，我们的数值实验表明，提出的框架通常会导致 MRI 图像重建的质量更好。