\begin{abstract}
Blood vessel segmentation and -tracing are essential tasks in many medical imaging applications. Although numerous methods exist, the prevailing segment-then-fix paradigm is fundamentally limited regarding its suitability for modelling the task of complete and topologically accurate vascular network reconstruction. 
We here propose an approach to extract  topologically more accurate vascular graphs from 3D image data, building upon highly successful ideas from the related biomedical tasks of cell segmentation and -tracking. Our approach first predicts voxel-wise vessel direction vectors joint with standard vessel segmentation masks. Second, to extract the vascular graph from these predictions, we introduce a direction-vector-guided extension of the TEASAR algorithm.
Our approach achieves state-of-the-art performance on three benchmark datasets, spanning both synthetic and real imagery.
We further demonstrate the applicability of our approach to challenging 3D micro-CT scans of rat heart vasculature.
Finally, we propose meaningful and interpretable measures of topological error, namely false splits and false merges for graphs. Overall, our approach substantially improves the topological accuracy of reconstructed vascular graphs, being able to separate closely apposed vessel segments and handle multiple vascular trees within a single volume.
\end{abstract}
