Compensation of motion artifacts in MR mammography by elastic deformation
Ingo Boesnach, Martin Haimerl, Harmut Friedburg, Thomas Beth · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2001
In contrast agent aided dynamic MR mammography, the diagnostic relevance of the subtraction images is often reduced by artifacts which arise from misalignment of successive images due to patient motion. In this article a new registration technique is presented to compensate such motion artifacts. For this purpose we use a three dimensional elastic deformation model, because patient motion usually is neither rigid nor takes place in parallel planes in contrast to other registration problems such as CT of the brain. For the registration, a set of control points is selected with locally high gradients being uniformly distributed over the mammae. A template based matching of small regions around the control points gives their optimal displacement vectors between the pre contrast and the post contrast image. The Delaunay triangulation of the control points defines a set of tetrahedra which are affinely transformed according to the displacements of their corners. The developed method works very fast and thus is suitable for high resolution MR devices. The evaluation with a synthetically transformed post contrast image results in a reduction of the mean error per voxel from 5.81 mm to 0.75 mm after registration.