Table 2.

Systematic and random error of 3DUS, CTV to PTV margin

		Lateral mm (95% CI)	Longitudinal mm (95% CI)	Vertical mm (95% CI)
Systematic errors
	3DUS	1.3 (0.8-3.3)	0.8 (0.5-2.1)	1.4 (0.9-3.6)
	CBCT (bone-match)	1.3 (0.8-3.1)	1.9 (1.2-4.6)	1.8 (1.4-5.4)
	Skin marks	1.6 (0.9-3.6)	2.2 (1.1-4.4)	2.3 (1.4-5.7)
Random errors
	3DUS	2.5 (0.0-3.8)	2.3 (0.0-3.5)	2.7 (0.0-4.4)
	CBCT (bone-match)	0.7 (0.0-1.3)	2.0 (0.0-3.6)	2.7 (0.0-4.8)
	Skin marks	2.2 (0.0-3.8)	2.9 (0.0-4.7)	3.9 (0.0-5.7)
Resulting optimal margins
	3DUS	5.1 (2.1-10.9)	3.7 (1.3-7.6)	5.5 (2.3-11.9)
	CBCT (bone-match)	3.7 (2.0-8.7)	6.1 (2.9-14.0)	6.3 (2.8-14.3)
	Skin marks	5.5 (2.4-12.2)	7.5 (3.4-16.8)	8.5 (3.6-18.1)

In units of mm; the systematic error is defined as the standard deviation of all individual mean errors; the random error is defined as the root of the average of all individual variances; the optimal margin is defined as 2.5 times the systematic error plus 0.7 times the random error.