Providing visual information to validate 2-D to 3-D registration

This paper addresses a key issue of providing clinicians with visual inform ation to validate the accuracy of 2-D/3-D registration for robot-assisted t otal hip replacement (THR) surgery. Although numerous registration approach es have been presented, the topic of registration validation has scarcely b een addressed in the literature. In practice, clinicians rely on post-opera tive X-rays to assess the accuracy of implant placement. Motivated by this, we simulate a set of post-operative X-ray images by superimposing the impl ant positioned pre-operatively onto the intra-operatively collected and cal ibrated images of the femur, through a transformation computed by the 2-D/3 -D registration. With these images, a judgment on the registration accuracy can be made. In addition, this paper introduces methods for superimposing pre-operative data on intra-operative X-ray images that were not corrected for distortion, by applying the same image distortion to the data. This pap er also introduces a new framework for incorporating surface normals in the objective function for registration. A comparison between marker-based and image-based registration is conducted. The advantage of our approach is th at the simulated post-operative X-ray images are very familiar to clinician s and, therefore, easy for them to interpret. As an added benefit, this tec hnique provides new means for comparing the marker-based and image-based re gistration for robot-assisted THR surgery. This approach can be extended to other interventions where intra-operative images are used for registration . (C) 2000 Elsevier Science B.V. All rights reserved.