Abstract: Apparatus for navigating an instrument through an anatomical structure of a patient's body volume, comprising a table for supporting the patient and at least a first C-arm having a first X-ray source and a first X-ray detector for acquiring a first series of 2D-images of the instrument whilst manoeuvering through said anatomical structure, and further comprising a processing unit for the images which unit connects to a memory device, whereby the memory device holds pre-determined 3D-images of the patient's anatomical structure, and the processing unit is arranged for processing the 2D-images of the instrument and the 3D-images of the anatomical structure so as to provide merged 3D-images of the instrument that in use manoeuvers through said anatomical structure.