Flow Matching-enabled Test-Time Refinement for Unsupervised Cardiac MR Registration

Fuente: arXiv
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Hauptverfasser: Fu, Yunguan, Bai, Wenjia, Yan, Wen, Clarkson, Matthew J, Davies, Rhodri Huw, Hu, Yipeng
Format: Preprint
Veröffentlicht: 2026
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author Fu, Yunguan
Bai, Wenjia
Yan, Wen
Clarkson, Matthew J
Davies, Rhodri Huw
Hu, Yipeng
author_facet Fu, Yunguan
Bai, Wenjia
Yan, Wen
Clarkson, Matthew J
Davies, Rhodri Huw
Hu, Yipeng
contents Diffusion-based unsupervised image registration has been explored for cardiac cine MR, but expensive multi-step inference limits practical use. We propose FlowReg, a flow-matching framework in displacement field space that achieves strong registration in as few as two steps and supports further refinement with more steps. FlowReg uses warmup-reflow training: a single-step network first acts as a teacher, then a student learns to refine from arbitrary intermediate states, removing the need for a pre-trained model as in existing methods. An Initial Guess strategy feeds back the model prediction as the next starting point, improving refinement from step two onward. On ACDC and MM2 across six tasks (including cross-dataset generalization), FlowReg outperforms the state of the art on five tasks (+0.6% mean Dice score on average), with the largest gain in the left ventricle (+1.09%), and reduces LVEF estimation error on all six tasks (-2.58 percentage points), using only 0.7% extra parameters and no segmentation labels. Code is available at https://github.com/mathpluscode/FlowReg.
format Preprint
id arxiv_https___arxiv_org_abs_2603_01073
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Flow Matching-enabled Test-Time Refinement for Unsupervised Cardiac MR Registration
Fu, Yunguan
Bai, Wenjia
Yan, Wen
Clarkson, Matthew J
Davies, Rhodri Huw
Hu, Yipeng
Computer Vision and Pattern Recognition
Diffusion-based unsupervised image registration has been explored for cardiac cine MR, but expensive multi-step inference limits practical use. We propose FlowReg, a flow-matching framework in displacement field space that achieves strong registration in as few as two steps and supports further refinement with more steps. FlowReg uses warmup-reflow training: a single-step network first acts as a teacher, then a student learns to refine from arbitrary intermediate states, removing the need for a pre-trained model as in existing methods. An Initial Guess strategy feeds back the model prediction as the next starting point, improving refinement from step two onward. On ACDC and MM2 across six tasks (including cross-dataset generalization), FlowReg outperforms the state of the art on five tasks (+0.6% mean Dice score on average), with the largest gain in the left ventricle (+1.09%), and reduces LVEF estimation error on all six tasks (-2.58 percentage points), using only 0.7% extra parameters and no segmentation labels. Code is available at https://github.com/mathpluscode/FlowReg.
title Flow Matching-enabled Test-Time Refinement for Unsupervised Cardiac MR Registration
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2603.01073