Blood flow turbulence or stationary blood can occur in vessels of the body, in particular following surgical interventions or minimally invasive interventional procedures, and this can lead to the formation of thrombi. A model of such vessels is obtained on the basis of a 3D image dataset, a simulation is then performed and a check carried out to determine whether turbulence or stationary blood can be demonstrated in the simulation. The model is then modified, successively where necessary, until the simulation reveals no more turbulence. Then, on the basis of the most recently modified model that results in no turbulence and no stationary blood, an aid is provided, in particular a specific aid such as e.g. a stent produced or a screen display presented.