Method for determining the position of an instrument with an x-ray system

1. A method for determining a position of an instrument in a structure of an object with a x-ray system, comprising:

providing a first 3D image data record of at least one area relevant for determining the position, the x-ray system is registered with the first 3D image data record;

recording at least one 2D x-ray image of the relevant area after introduction of the instrument into the structure and from at least one projection direction with a known projection geometry with the x-ray system;

recording a 2D position of a first location of the instrument in the 2D x-ray image with a projection line running in accordance with the known projection geometry being placed at the 2D position through the first 3D image data record or second 3D data record derived from it;

using a processor to determine a 3D position of the first location of the instrument in the first 3D image data record or second 3D data record from an intersection of the projection line with the structure; and,

wherein the intersection of the projection line with the structure is determined to locate the structure in which the instrument is positioned, and

wherein the projection line intersects with a number of different structures providing a number of maxima and/or minima of grey level values along the projection line in the first 3D image data record or second 3D image data record, said determining the 3D position of the first location of the instrument including analyzing the grey level values.

2. The method in accordance with claim 1 , wherein the object is a hollow canal or a hollow organ.

3. The method in accordance with claim 1 , wherein the first 3D image data record is recorded with the x-ray system or another imaging modality.

4. The method in accordance with claim 1 , wherein the second 3D data record is obtained from the first 3D data record by segmenting the structure.

5. The method in accordance with claim 1 , wherein for a number of intersections of the projection line with the structure, the position of an intersection is selected as a 3D position which emerges as the most probable position taking into account at least one previous determination.

6. The method in accordance with claim 1 , wherein at least one further 2D position of at least one further location of the instrument is recorded in the 2D x-ray image, at least one further projection line running in accordance with the known protection geometry is placed through the first 3D image data record or second 3D image data record at the at least one further 2D position, and a 3D position of the at least one further location of the instrument is determined from an intersection of the at least one further projection line with the structure.

7. The method in accordance with claim 6 , wherein for a number of intersections of the first projection line with the structure, the position of one of the number of intersections is selected as the 3D position which, taking into consideration the intersection or intersections of the further projection line or projection lines counts as the most probable position.

8. The method in accordance with claim 1 , wherein for a number of intersections of the projection line with the structure, the selection of the position of an intersection as a 3D position is possible by user interaction.

9. The method in accordance with claim 1 , wherein for intersections which extend over a number of positions in the first 3D image data record or second 3D data record, an average position is selected as the 3D position.

10. The method in accordance with claim 1 , wherein the 2D x-ray image is recorded with a monoplanar x-ray system.

11. The method in accordance with claim 1 , wherein a biplanar x-ray system or an x-ray system with a detector and two x-ray focuses is used as an x-ray system, with which at least two 2D x-ray images being recorded from a different projection direction and evaluated for determining the 3D position.