US Patent 7556428 Surgical navigation system including patient tracker with removable registration appendage

A surgical navigation system includes a CT scanner that takes a plurality of x-ray images of a patient. A patient tracker including locators is attached to the patient, and a registration appendage is removably secured to the patient tracker in a known position and orientation. The registration appendage includes radio-opaque markers arranged in a predetermined geometric pattern. The registration appendage is viewable in a CT scan in situations where the locators of the patient tracker are outside of a field of view of the CT scanner.