Registration of time-separated x-ray images

A method of correlating images taken at different times, comprising:

• segmenting, in a first image of a plurality of rigid elements taken at a first time and in a second image of the plurality of rigid elements taken at a second time after the first time, each rigid element of the plurality of rigid elements;
• calculating a homography for each rigid element of the plurality of rigid elements to yield a set of homographies, each homography correlating the rigid element as depicted in the first image to the rigid element as depicted in the second image;
• arranging the set of homographies into homography clusters based on at least one characteristic;
• selecting a homography cluster based on at least one parameter;
• and
• projecting each of the plurality of rigid elements as depicted in the second image onto the first image using a mean of the selected homography cluster to yield a projection image.

A system for comparing images, comprising:

• at least one processor;
• and
• a memory storing instructions for execution by the processor that, when executed, cause the processor to:
• identify a plurality of elements in a first image generated at a first time;
• identify the plurality of elements in a second image generated at a second time after the first time;
• calculate a homography for each one of the plurality of elements, using the first image and the second image, to yield a set of homographies;
• and
• determine, based on the set of homographies, a first change in pose of one or more of the plurality of elements in the second image relative to the first image that is attributable to a change in imaging device position, relative to the plurality of elements, from the first image to the second image, and a second change in pose of at least one of the plurality of elements in the second image relative to the first image that is not attributable to the change in imaging device position.