1. An apparatus for registering medical image data representing a tubular structure, comprising: a data processing unit for obtaining first medical image data representing the tubular structure and second medical image data representing the tubular structure; a region identification unit for identifying the tubular structure in the first medical image data, defining in the first medical image data a volumetric region of interest comprising the tubular structure along at least part of the length of the tubular structure and defining a subset of the first medical image data corresponding to the volumetric region of interest; and a registration unit for performing a registration of the subset of the first medical image data with at least some of the second medical image data, wherein the registration comprises at least one of a rigid registration and an affine registration.