1. A system for planning an arterial stenosis therapy comprising: a processor configured to receive a first volumetric data set of at least part of an artery, said part comprising a stenosis; receive at least one two-dimensional data of the stenosis; receive first arterial pressure drop information, said first arterial pressure drop information being an arterial pressure drop around the stenosis; register the first volumetric data set with the at least one two-dimensional data to obtain a second volumetric data set; generate a third volumetric data set by modifying a geometry of the stenosis in the second volumetric data set; and estimate a second arterial pressure drop around the stenosis in the third volumetric data set.