用流匹配提升CT图像重建,速度更快质量更高。
Physics-Guided Flow Matching for CT Image Reconstruction

- 采用高分辨率流匹配模型,结合分阶段训练策略增强图像结构保真度。
- 在多种低剂量CT重建任务中,PSNR、SSIM和视觉质量均优于扩散模型。
- 只需更少采样步骤即可生成高质量图像,适合临床高效重建场景。
深度生成模型近年来成为解决CT中不适定逆问题的强大先验,基于扩散的方法已达到最先进性能。然而,扩散模型通常依赖随机采样过程、长推理轨迹和精细调校的噪声调度,限制了计算效率与数值稳定性,尤其在高空间分辨率下。本文探索流匹配作为CT重建的替代生成先验。我们在256x256胸腔图像上训练了一个高分辨率修正流匹配模型,数据来自梅奥诊所低剂量CT数据集。为缓解过拟合与解剖变异不足的问题,采用两阶段训练策略:第一阶段使用强解剖引导的数据增强,第二阶段减少或去除增强以精炼结构保真度。所获模型能生成高质量且解剖一致的类CT图像,构成强大学习先验。随后评估多种专为流匹配设计的重建方法,包括Plug-and-Play Flow、FlowDPS、Flower和Flow-Priors (ICTM),并与最先进的扩散模型方法(如DDRM、DPS、DiffPIR)对比。实验结果表明,在多个CT逆问题设置中,基于流匹配的方法在PSNR、SSIM和感知质量上持续优于扩散方法,且采样步数更少。最后,我们公开发布训练好的流匹配模型及配套代码,以促进可复现性与未来研究。总体而言,本工作证明流匹配是高分辨率CT图像重建中稳定、高效且有效的扩散模型替代方案。
原文摘要 · Abstract (English)
Deep generative models have recently emerged as powerful priors for solving ill-posed inverse problems in CT, with diffusion-based approaches achieving state-of-the-art reconstruction performance. However, diffusion models typically rely on stochastic sampling procedures, long inference trajectories, and carefully tuned noise schedules, which can limit computational efficiency and numerical stability, especially at high spatial resolutions. In this work, we investigate Flow Matching as an alternative generative prior for CT reconstruction. We train a high-resolution Rectified Flow Matching model on 256x256 chest images from the Mayo Clinic Low-Dose CT dataset. To mitigate overfitting and limited anatomical variability, we employ a two-stage training strategy consisting of an initial phase with strong, anatomically informed data augmentation, followed by a fine-tuning phase with reduced or no augmentation to refine structural fidelity. The resulting model is capable of generating high-quality and anatomically coherent CT-like images, serving as a strong learned prior. We then evaluate multiple reconstruction methods specifically designed for Flow Matching models, including Plug-and-Play Flow, FlowDPS, Flower, and Flow-Priors (ICTM), and compare them against state-of-the-art diffusion-based reconstruction algorithms such as DDRM, DPS, and DiffPIR. Experimental results across several CT inverse problem settings show that Flow Matching-based approaches consistently outperform diffusion-based methods in terms of PSNR, SSIM, and perceptual quality, while requiring fewer sampling steps. Finally, we publicly release the trained Flow Matching model and accompanying code to facilitate reproducibility and future research. Overall, this work demonstrates that Flow Matching provides a stable, efficient, and effective alternative to diffusion models for high-resolution CT image reconstruction.
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