Diffusion models face significant challenges when employed for large-scale medical image reconstruction in real practice such as 3D Computed Tomography (CT). Due to the demanding memory, time, and data requirements, it is difficult to train a diffusion model directly on the entire volume of high-dimensional data to obtain an efficient 3D diffusion prior. Existing works utilizing diffusion priors on single 2D image slice with hand-crafted cross-slice regularization would sacrifice the z-axis consistency, which results in severe artifacts along the z-axis. In this work, we propose a novel framework that enables learning the 3D image prior through position-aware 3D-patch diffusion score blending for reconstructing large-scale 3D medical images. To the best of our knowledge, we are the first to utilize a 3D-patch diffusion prior for 3D medical image reconstruction. Extensive experiments on sparse view and limited angle CT reconstruction show that our DiffusionBlend method significantly outperforms previous methods and achieves state-of-the-art performance on real-world CT reconstruction problems with high-dimensional 3D image (i.e., $256 \times 256 \times 500$). Our algorithm also comes with better or comparable computational efficiency than previous state-of-the-art methods.

通过位置感知的三维图像块扩散评分融合，本文提出了一种新的框架，能够学习三维图像的先验进行大规模三维医学图像重建，实验表明我们的方法在稀疏视图和有限角度的CT重建上显著优于先前的方法，并且在高维三维图像（$256 	imes 256 	imes 500$）的实际CT重建问题上获得了最先进的性能，同时算法具有更好或相当的计算效率。

DiffusionBlend: 通过位置感知扩散分数混合学习三维图像先验，用于三维计算机断层扫描重建