Diffusion Bridge Networks Simulate Clinical-grade PET from MRI for Dementia Diagnostics

Yitong Li; Ralph Buchert; Benita Schmitz-Koep; Timo Grimmer; Björn Ommer; Dennis M. Hedderich; Igor Yakushev; Christian Wachinger

arXiv · 2510.15556

Diffusion Bridge Networks Simulate Clinical-grade PET from MRI for Dementia Diagnostics

Yitong Li·Ralph Buchert·Benita Schmitz-Koep·Timo Grimmer·Björn Ommer·Dennis M. Hedderich·Igor Yakushev·Christian Wachinger

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Abstract

Positron emission tomography (PET) with 18F-Fluorodeoxyglucose (FDG) is an established tool in the diagnostic workup of patients with suspected dementing disorders. However, compared to the routinely available magnetic resonance imaging (MRI), FDG-PET remains significantly less accessible and substantially more expensive. Here, we present SiM2P, a 3D diffusion bridge-based framework that learns a probabilistic mapping from MRI and auxiliary patient information to simulate FDG-PET images of diagnostic quality. In a blinded clinical reader study, two neuroradiologists and two nuclear medicine physicians rated the original MRI and SiM2P-simulated PET images of patients with Alzheimer's disease, behavioral-variant frontotemporal dementia, and cognitively healthy controls. SiM2P significantly improved the overall diagnostic accuracy of differentiating between three groups from 75.0% to 84.7% (p<0.05). Notably, the simulated PET images received higher diagnostic certainty ratings and achieved superior interrater agreement compared to the MRI images. Finally, we developed a practical workflow for local deployment of the SiM2P framework. It requires as few as 20 site-specific cases and only basic demographic information. This approach makes the established diagnostic benefits of FDG-PET imaging more accessible to patients with suspected dementing disorders, potentially improving early detection and differential diagnosis in resource-limited settings. Our code is available at https://github.com/Yiiitong/SiM2P.

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Yitong Li, Ralph Buchert, Benita Schmitz-Koep, Timo Grimmer, Björn Ommer, Dennis M. Hedderich, Igor Yakushev, Christian Wachinger. 2025-10-17. Diffusion Bridge Networks Simulate Clinical-grade PET from MRI for Dementia Diagnostics. https://arxiv.org/abs/2510.15556

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