Abstract: A registration fixture for use with a surgical navigation system for registration of medical images to a three-dimensional tracking space includes a base frame adapted to be mounted over a flat panel detector of an x-ray medical imaging device, and a side frame having optical tracking markers mounted to the base frame. The base frame includes a first set of radiopaque markers embedded therein in a first predetermined pattern and arranged on a plane, and a second set of radiopaque markers embedded therein in a second predetermined pattern also arranged on another plane, which is spaced from the first set of radiopaque markers. The side frame has a plurality of optical tracking markers and is configured to detachably mount to the base frame.