PET Image Denoising via Text-Guided Diffusion: Integrating Anatomical Priors through Text Prompts

Low-dose Positron Emission Tomography (PET) imaging presents a significant challenge due to increased noise and reduced image quality, which can compromise its diagnostic accuracy and clinical utility. Denoising diffusion probabilistic models (DDPMs) have demonstrated promising performance for PET image denoising. However, existing DDPM-based methods typically overlook valuable metadata such as patient demographics, anatomical information, and scanning parameters, which should further enhance the denoising performance if considered. Recent advances in vision-language models (VLMs), particularly the pre-trained Contrastive Language-Image Pre-training (CLIP) model, have highlighted the potential of incorporating text-based information into visual tasks to improve downstream performance. In this preliminary study, we proposed a novel text-guided DDPM for PET image denoising that integrated anatomical priors through text prompts. Anatomical text descriptions were encoded using a pre-trained CLIP text encoder to extract semantic guidance, which was then incorporated into the diffusion process via the cross-attention mechanism. Evaluations based on paired 1/20 low-dose and normal-dose 18F-FDG PET datasets demonstrated that the proposed method achieved better quantitative performance than conventional UNet and standard DDPM methods at both the whole-body and organ levels. These results underscored the potential of leveraging VLMs to integrate rich metadata into the diffusion framework to enhance the image quality of low-dose PET scans.