A system for tracking an interventional device, the system comprising: - an interface unit ; - a data storage unit ; - a processing unit ; and - an output unit ; wherein the interface unit is configured to provide at least two current 2D images of a region of interest of a subject acquired with optical cameras in at least two different viewing directions; wherein the 2D images show an instrument in the region of interest, wherein the instrument has a geometry that comprises a rigid cylinder; wherein the processing unit is configured to spatially register the 2D images with pre-interventional 3D data of the region of interest of the subject; to identify at least one straight line, representing the instrument, in each of the at least two current 2D images; to determine an instrument 3D line based on the identified at least one straight line in each of the at least two current 2D images" and to project the instrument 3D line on the pre-interventional 3D data generating a combined navigation image, wherein the output unit is configured to provide the combined navigation image to the user, and wherein, for the identifying of the at least one straight line, the processing unit is configured to use a planned instrument path in the pre-interventional 3D scan to define a search region for line identification in the at least two current 2D images. - an interface unit ; - a data storage unit ; - a processing unit ; and - an output unit ; wherein the interface unit is configured to provide at least two current 2D images of a region of interest of a subject acquired with optical cameras in at least two different viewing directions; wherein the 2D images show an instrument in the region of interest, wherein the instrument has a geometry that comprises a rigid cylinder; wherein the processing unit is configured to spatially register the 2D images with pre-interventional 3D data of the region of interest of the subject; to identify at least one straight line, representing the instrument, in each of the at least two current 2D images; to determine an instrument 3D line based on the identified at least one straight line in each of the at least two current 2D images" and to project the instrument 3D line on the pre-interventional 3D data generating a combined navigation image, wherein the output unit is configured to provide the combined navigation image to the user, and wherein, for the identifying of the at least one straight line, the processing unit is configured to use a planned instrument path in the pre-interventional 3D scan to define a search region for line identification in the at least two current 2D images. wherein the interface unit is configured to provide at least two current 2D images of a region of interest of a subject acquired with optical cameras in at least two different viewing directions; wherein the 2D images show an instrument in the region of interest, wherein the instrument has a geometry that comprises a rigid cylinder; wherein the processing unit is configured to spatially register the 2D images with pre-interventional 3D data of the region of interest of the subject; to identify at least one straight line, representing the instrument, in each of the at least two current 2D images; to determine an instrument 3D line based on the identified at least one straight line in each of the at least two current 2D images" and to project the instrument 3D line on the pre-interventional 3D data generating a combined navigation image, wherein the output unit is configured to provide the combined navigation image to the user, and wherein, for the identifying of the at least one straight line, the processing unit is configured to use a planned instrument path in the pre-interventional 3D scan to define a search region for line identification in the at least two current 2D images. <EOS>