Method for superimposing a two-dimensional x-ray image on projective images of three-dimensional structures

A method for processing a three-dimensional image data set with two-dimensional X-ray images captured by an X-ray machine, the method comprising:

• providing a three-dimensional image data set of at least one examination zone in which anatomical structures are present;
• segmenting the three-dimensional image data set to provide a three-dimensional vascular structure model describing a vascular structure and a three-dimensional bone structure model describing a bone structure;
• recording a first two-dimensional X-ray image containing at least a portion the bone structure and at least a portion of the vascular structure using a recording geometry and in the presence of a first contrast agent concentration;
• recording a second two-dimensional X-ray image of the examination zone, the second two-dimensional X-ray image containing a second contrast agent concentration that is different from the first contrast agent concentration, wherein the recording of the second two-dimensional X-ray image takes place using the same recording geometry as the first two-dimensional X-ray image;
• subtracting the first and second X-ray images to generate a subtraction image, wherein the subtraction image includes the vascular structure;
• and
• determining an optimum projective geometry using a three-part target function,
• wherein a first part of the three-part target function represents a similarity between a forward projection of the bone structure model of the three-dimensional image data set and the bone structure in at least one of the first and second X-ray images, while varying an assumed projective geometry,
• wherein a second part of the three-part target function represents a similarity between a forward projection of the vascular structure model of the three-dimensional image data set and the vascular structure of the subtraction image, while varying the assumed projective geometry, and
• wherein a third part of the three-part target function represents a similarity between all image data of the forward projection of the three-dimensional image data set and all image data of at least one of the first and second X-ray images, while varying the assumed projective geometry.