It is hypothesized that the uncertainty of the SynchronyRTM model from the rotation of a geometrically asymmetrical single fiducial shall be non-zero during the motion tracking. To validate this hypothesis, the uncertainty was measured for a SynchronyRTM model built for a respiratory motion phantom oriented at different yaw angles on a Cyberknife RTM treatment table.

A Mini-ball Cube RTMwith three cylindrical GoldMark(TM) (1mmx5mm Au) numbered fiducials was placed inside a respiratory phantom and used for all tests. The fiducial with the least artifact interference was selected for the motion tracking. A 2cm periodic, longitudinal, linear motion of the Mini-ball cube was executed and tested for yaw rotational angles, 0° -- 90°. The test was repeated over 3 nonconsecutive days. The uncertainty increased with the yaw angle with the most noticeable changes seen between20° and 60° yaw, where uncertainty increased from 23.5% to 57.9%. A similar test was performed using a spherical Gold Anchor(TM) fiducial. The uncertainties found when using the Gold Anchor(TM) were statistically lower than those found when using the GoldMark(TM) fiducial for all angles of rotation. For the first time, it is found that SynchronyRTM model uncertainty depends on fiducial geometry. In addition, this research has shown that tracking target rotation using a single fiducial can be accomplished with the SynchronyRTM model uncertainty as it is displayed on the treatment console. The results of this research could lead to decreased acute toxicity effects related to multiple fiducials.