Table 4.

Shifts of a head phantom as preset by the robotic couch and as detected by both ExacTrac and CBCT (N = 24, resp. 8 per axis)

Discrepancy between …	… ExacTrac and robotic couch	… CBCT and robotic couch	… ExacTrac and CBCT
lateral	0.0 ± 0.5 (p = 0.9)	0.0 ± 0.6 (p = 1.0)	0.0 ± 0.1 (p = 0.5)
longitudinal	0.4 ± 0.3 (p = 0.1)	0.3 ± 0.3 (p = 0.1)	0.1 ± 0.1 (p = 0.3)
vertical	0.0 ± 0.4 (p = 0.9)	0.0 ± 0.4 (p = 1.0)	0.0 ± 0.1 (p = 0.5)
radial	0.7 ± 0.3 (p = 0.007)	0.7 ± 0.3 (p = 0.006)	0.1 ± 0.0 (p < 0.001)

All units are in mm, average ± SD (p values from two-sided t-test)