Table 1.

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

	No Off‐line Correction $(N=20)$	NAL $(N=20)$	FVCP $(N=20)$
${\mu }_{\mathrm{P}}$ (mm)	$-4.3$	$-4.3$	0.5
${\mathrm{\Sigma }}_{\mathrm{P}}$ (mm)	5.7	4.1	1.8
${\sigma }_{\mathrm{P}}$ (mm)	4.6	3.4	2.2
PTV (mm)	17.5	12.7	6.0
Number of corrections	0	20	20

$\text{WBRT}=$ whole‐breast radiotherapy; ${\mu }_{\mathrm{P}}=$ population mean setup error; ${\mathrm{\Sigma }}_{\mathrm{P}}=$ systematic setup error; ${\sigma }_{\mathrm{P}}=$ random setup error; $\text{PTV}=$ planning target volume; $\text{NAL}=$ no‐action‐level; $\text{FVCP}=$ fixed vertical couch position.