Table 2.

Recommendation of nonuniform PTV margins for prostate bed in 3 directions based on derived error values of superior and inferior portions

PTV margin (cm)	Superior 2.5Σ + 0.7σ	Inferior 2.5Σ + 0.7σ	Margin recommendation with simplified rounding off
LR	0.19	0.10	0.2
AP	0.89	0.44	0.9/0.4 (sup/inf)
SI	0.76	0.67	0.7

Abbreviations: AP = anterior–posterior; LR = left–right; PTV = planning target volume; SI = superior–inferior.