TABLE 2.

Inter‐ and intrafractional errors, and calculated setup margins in dependence on the frequency of online verifications.

			Interfractional error			Intrafractional error			Setup margin a
Direction		Frequency of online verifications using kV–CBCT	M	Σ	σ	M	Σ	σ	Inter‐fractional error	Intra‐fractional error	Combined inter‐ and intra‐fractional error
Translational error (mm)
	LAT	None	−0.2	0.9	1.8	0.0	0.6	0.9	3	2	4
	LNG	None	0.4	1.6	2.4	0.1	0.6	1.0	5	2	6
	VRT	None	−0.6	1.3	1.6	0.1	0.4	0.6	4	1	4
	LAT	1/week	0.0	0.8	1.7	0.0	0.6	0.9	3	2	3
	LNG	1/week	0.2	1.5	2.2	0.1	0.6	1.0	5	2	5
	VRT	1/week	−0.6	1.0	1.5	0.1	0.4	0.6	3	1	3
	LAT	Every other day	0.0	0.5	1.4	0.0	0.6	0.9	2	2	3
	LNG	Every other day	0.3	1.0	1.9	0.1	0.6	1.0	3	2	4
	VRT	Every other day	−0.3	0.6	1.3	0.1	0.4	0.6	2	1	2
Rotational error (°)
	LAT	None	0.3	0.6	0.7	0.2	0.7	0.5	–	–	–
	LNG	None	0.2	0.7	0.6	0.2	0.7	0.6	–	–	–
	VRT	None	−0.1	0.8	0.4	0.4	0.8	0.7	–	–	–
	LAT	1/week	0.2	0.6	0.5	0.2	0.7	0.5	–	–	–
	LNG	1/week	0.1	0.7	0.4	0.2	0.7	0.6	–	–	–
	VRT	1/week	0.0	0.7	0.3	0.4	0.8	0.7	–	–	–
	LAT	Every other day	0.1	0.5	0.3	0.2	0.7	0.5	–	–	–
	LNG	Every other day	0.1	0.5	0.3	0.2	0.7	0.6	–	–	–
	VRT	Every other day	0.0	0.6	0.2	0.4	0.8	0.7	–	–	–

Abbreviations: kV‐CBCT, Kilovoltage cone beam computed tomography; LAT, lateral; LNG, longitudinal; M, overall population mean set‐up error; VRT, vertical; Σ, population systematic error; σ, population random error.

^a Calculated setup margins according to the van Herk formula.