Table 2.

Measured mediolateral and superior–inferior setup errors without off‐line setup correction during fractions 1–5 in WBRT. Simulated mediolateral and superior–inferior residual setup errors and number of corrections obtained for different off‐line setup correction protocols applied during fractions 6–10 in WBRT

	ML $(N=20)$						SI $(N=19)$
	No Off‐line Correction	NAL		FAL			No Off‐line Correction	NAL		FAL
Threshold (mm)	–	0.0	1.5	2.5	3.5	4.5	–	0.0	1.5	2.5	3.5	4.5
${\mu }_{\mathrm{P}}$ (mm)	$-0.02$	0.2	0.02	$-0.2$	0.1	0.1	1.0	$-0.08$	$-0.3$	0.1	0.1	0.6
${\mathrm{\Sigma }}_{\mathrm{P}}$ (mm)	3.4	1.3	1.4	1.3	1.6	2.2	3.3	2.7	2.7	2.6	2.6	3.1
${\sigma }_{\mathrm{P}}$ (mm)	2.3	2.6	2.6	2.6	2.6	2.6	3.1	3.3	3.3	3.3	3.3	3.3
PTV (mm)	10.1	5.1	5.4	5.1	5.7	7.4	10.4	9.2	9.0	8.8	8.8	10.2
Number of Corrections	0	20	14	12	8	4	0	19	12	7	7	3

$\text{WBRT}=$ whole‐breast radiotherapy; ${\mu }_{\mathrm{P}}=$ population mean setup error; ${\mathrm{\Sigma }}_{\mathrm{P}}=$ systematic setup error; σ_P = random setup error; PTV = planning target volume; ML = mediolateral; SI = superior‐inferior; NAL = no‐action‐level; FAL = fixed action level.