Figure 1.

Elekta 8 mm ball‐bearing (BB) phantom (a) mounted to the treatment couch. An example of table rotation analysis (b) with the BB phantom using in‐house MATLAB script. CW = clockwise; CCW = counter‐clockwise. The fit circles for the CW and CCW trajectories are shown. A‐B indicates the A‐side and B‐side, respectively, corresponding to the patient right and left side at supine orientation. G‐T stands for the gun and target direction, respectively. The maximum deviation of the BB phantom during rotation to the radiation isocenter was also derived, indicated as max error in the figure.