NeCS-Flow: Necrosis-Guided Contrast-Enhanced MRI Synthesis with Rectified-Flow Refinement

NeCS-Flow synthesizes gadolinium-free post-contrast T1w brain MRI for adult-type gliomas, improving enhancing tumor Dice via necrotic scaling (HGG 0.793→0.816 internal; 0.465→0.612 external).

• Why it matters: Gadolinium contrast raises deposition, adverse reaction, and cost concerns, while reliable gadolinium-free post-contrast imaging and diagnostic equivalence remain challenging.
• What they did: A three-stage retrospective pipeline used nnU-Net necrotic core segmentation, necrotic-scaling-guided U-Net contrast synthesis, and Posterior-Mean Rectified Flow refinement, trained on 374 patients and validated on 60 internal and 20 external.
• The result: PMRF refinement improved perceptual realism (lower FID and KID), and blinded three-reader accuracy was only modestly above chance (61.7%) with no significant clinical-metric differences between real and synthetic images.