Same Branches, Different Trees: A Bifurcation Connectedness Metric for Coronary Artery Segmentation and FFR-CT Decision Agreement

TL;DR - This paper proposes the Bifurcation Connectedness Score (BCS) for coronary artery segmentation, measuring vessel-tree connectivity that overlap metrics can miss. Better BCS correlates with closer FFR-CT treatment-decision agreement, especially in severe disease.

• BCS evaluates connectivity at each ground-truth bifurcation and strongly detects localized vessel breaks.
• It remains largely stable under narrowing that preserves connectivity, distinguishing topology from volumetric overlap.
• Higher BCS was associated with better predicted-versus-ground-truth FFR-CT decision agreement in severe disease (OR 2.16, CI [1.23, 4.18]).
• Soft-BCS provides a differentiable training surrogate; results suggest branch recovery and branch connectivity should be reported separately.