Table 5. Six Degrees of Freedom Couch Shifts Based on Daily Image Guidance with CBCT and OSMS.

*Representative real-time delta shifts across non-coplanar treatment couch angles

OSMS = optical surface monitoring system; CBCT = cone beam CT; FSRT = fractionated stereotactic radiotherapy

	Mean Translational Shifts (mm)			Mean Rotational Shifts (°)
	Vertical	Longitudinal	Lateral	Pitch	Roll	Rotation
Localization CBCT	3.1 (1.7 to 5.4)	0.34 (-0.4 to 1.3)	1.0 (0.5 to 1.5)	0.4 (0.1 to 0.7)	0.1 (0 to 0.2)	-0.1 (-0.3 to 0.2)
Setup OSMS	5.4	-0.40	0.96	0.07	-0.08	0.18
Verification CBCT	0	0.15	-0.3	0.05	0.05	0
Intrafraction OSMS*	0.30	-0.29	0.02	0	-0.01	0.07
Post-FSRT CBCT	-0.2	0.85	-0.25	0.2	0.05	0.15