This video is related to the scientific publication: “Blood flow clustering and applications in virtual stenting of intracranial aneurysms” by Steffen Oeltze (department of Simulation and Graphics, faculty of Computer Science, University of Magdeburg, Germany) et al. The blood flow in a saccular side-wall aneurysm has been simulated based on the vascular morphology extracted from patient-individual data. The resulting flow data is often visualised by a dense and cluttered set of streamlines. Clustering the streamlines and computing cluster representatives reduces visual clutter and exposes characteristic flow structures. The resulting flow summary benefits the assessment of aneurysmal haemodynamics. If a virtual stent is deployed and the simulation is repeated, a comparison of the flow summaries supports a prediction of the treatment success.