1. A method for determining a three-dimensional position and angular orientation of a catheter from two-dimensional x-ray images, comprising: a) generating a first x-ray image; b) pre-processing the first x-ray image to accentuate the imaging structures of the catheter in the x-ray image; c) generating a three-dimensional template for the catheter based on known dimensional characteristics of the catheter; d) initializing three parameters for the position and three parameters for the angular orientation of the catheter relative to the pre-processed x-ray image; e) generating, by a data processing unit, a two-dimensional projection of the template with reference to the six parameters for position and angular orientation of the catheter; f) comparing, by a data processing unit, the two-dimensional projection with the pre-processed x-ray image; g) determining, by a data processing unit, a similarity between the two-dimensional projection and the pre-processed x-ray image based on the comparison; h) aborting, by a data processing unit, the procedure if the similarity exceeds a predetermined threshold and establishing the initialized position and orientation parameters as the actual position and orientation of the catheter in the x-ray image; i) repeating steps e) through h) in an optimization loop until the degree of similarity exceeds a predetermined threshold, j) obtaining, by a data processing unit, a first projection line based on the six position and orientation parameters obtained with the first x-ray image via a back-projection of the catheter from the first x-ray image into the three-dimensional space; k) obtaining, by a data processing unit, a second projection line based on the six position and orientation parameters based on the second x-ray image via a back-projection of the object from the second x-ray image into the three-dimensional space; l) determining, by a data processing unit, the location with the smallest quadratic distance to the two projection lines; and m) determining, by a data processing unit, an intersection point that locates the catheter in three-dimensional space.