15. An apparatus for determining a position in an image, comprising: a display for displaying a volume rendering of image data acquired from an object, a pointing unit for pointing at a structure of interest displayed in the volume rendering of the image data, and a processing unit for generating a viewing ray profile comprising information characterizing a ray running through said structure of interest, selecting a contextual profile from a list of contextual profiles, each of said contextual profiles comprising a representative ray profile representing a viewing ray profile of a structure, and comprising profile information, and determining a position within said structure of interest based on said profile information of said selected contextual profile in the case that the representative ray profile of said selected contextual profile matches at least a part of said viewing ray profile.
19. The apparatus according to claim 15 , wherein the representative ray profile is a pre-defined template.