Determining a registration between a 3D image and a set of at least two 2D images

A processing unit comprising:

• a processor configured to determine or update a registration between a three-dimensional (3D) image of a region of interest and a set of at least two two-dimensional (2D) images of the same region of interest, wherein the at least two 2D images are acquired using different imaging geometries, wherein the registration is described by a set of registration parameters, the determination comprising:
• selection of at least one respective contour point in the 3D image for each of the at least two 2D images;
• determination of a 2D position of a respective depiction of each contour point in the respective 2D image;
• for each contour point, determination of at least one condition for registration parameters that needs to be fulfilled to map the respective contour point to the respective 2D position in the respective 2D image;
• and
• determination of an updated set of registration parameters, the determination of the updated set of registration parameters comprising solving a set of equations or an optimization problem that depends on the conditions.

A non-transitory computer-readable storage medium storing instructions executable by one or more processor to determine or update a registration between a three-dimensional (3D) image of a region of interest and a set of at least two two-dimensional (2D) images of the same region of interest, wherein the at least two 2D images are acquired using different imaging geometries, and wherein the registration is described by a set of registration parameters, the instructions stored in the non-transitory computer-readable storage medium comprising:

• selecting at least one respective contour point in the 3D image for each of the at least two 2D images;
• determining a 2D position of a respective depiction of each contour point in the respective 2D image;
• for each contour point, determining at least one condition for registration parameters that needs to be fulfilled to map the respective contour point to the respective 2D position in the respective 2D image;
• and
• determining an updated set of registration parameters, the determining of the updated set of registration parameters comprising solving a set of equations or an optimization problem that depends on the conditions.