A system and method of assisting a treatment procedure is provided, the method comprising the steps of determining a 3-D intervention vector in relation to an inner body structure of a body of interest based on a 3-D x-ray image, determining a 3-D position of an entry point on an outer surface of the body of interest based on the intervention vector, comparing the position and/or orientation of the inner body structure in the 3-D x-ray image with the position and/or orientation of the inner body structure in an additional 2-D x-ray image being generated transverse to the intervention vector, correcting the 3-D position of the entry point on the outer surface of the body of interest based on a deviation detected in the comparing step.