In a medical viewing system having an X-ray image acquisition device a data processing unit is adapted for generating two different views on a three-dimensional image set wherein a first view is corresponding to the viewing direction of the X-ray image acquisition device and a second view has a rotational offset to the first viewing direction. The first view may include live X-ray images e.g. for monitoring a stent placement. The second view 10 supports a clinician to unambigously judge whether ostia connection points may be blocked that are not clearly visible in anterior-posterior images. Fig.2
