DuoPrior-CFFlow: Dual-Prior Coarse-to-Fine Flow Matching for 3D OCT-to-OCTA Translation

Optical coherence tomography angiography (OCTA) provides clinically valuable retinal vascular information but remains more difficult to acquire than structural optical coherence tomography (OCT), motivating reliable OCT-to-OCTA transla- tion. Three-dimensional OCT-to-OCTA translation is challenging because it must simultaneously preserve continuous global retinal structure and recover sparse, fine vascular details. We propose DuoPrior-CFFlow, a dual-prior coarse-to-fine flow-matching framework for paired three-dimensional OCT-to-OCTA transla- tion. Its CF-Flow path decomposes volumetric representations into low- and high- frequency components, modeling global structural transport with Coarse Flow and vascular-detail transport with Fine Flow. The multi-scale Z-aware (MSZ) prior provides global depth, local depth, and depth-gradient cues for structural guid- ance, while VesselAux promotes three-dimensional vascular consistency through auxiliary vessel supervision. DuoPrior-CFFlow outperforms the directly compa- rable baselines on most quantitative metrics and better preserves retinal vascular structures. Structural preservation and downstream utility evaluations show that our translated 3D OCTA volumes achieve the highest 3D vessel-mask consistency, the lowest vascular occupancy in the foveal avascular zone, and the highest disease classification accuracy. Code is available at https://anonymous.4open.science/r/duoprior-cfflow-code-6D9F/.