Image-based marker tracking and registration for intraoperative 3D image-guided interventions using augmented reality

Augmented reality (AR) can enable physicians to "see" inside of patients by projecting cross-sectional imaging directly onto the patient during procedures. In order to maintain workflow, imaging must be quickly and accurately registered to the patient. We describe a method for automatically registering a CT image set projected from an augmented reality headset to a set of points in the real world as a first step towards real-time registration of medical images to patients. Sterile, radiopaque fiducial markers with unique optical identifiers were placed on a patient prior to acquiring a CT scan of the abdomen. For testing purposes, the same fiducial markers were then placed on a tabletop as a representation of the patient. Our algorithm then automatically located the fiducial markers in the CT image set, optically identified the fiducial markers on the tabletop, registered the markers in the CT image set with the optically detected markers and finally projected the registered CT image set onto the real-world markers using the augmented reality headset.The registration time for aligning the image set using 3 markers was 0.9 +/- 0.2 seconds with an accuracy of 5 +/- 2 mm. These findings demonstrate the feasibility of fast and accurate registration using unique radiopaque markers for aligning patient imaging onto patients for procedural planning and guidance.