Table 3.

Safety margins attributed to interfractional prostate motion (see Table 1) calculated with the van Herk formula (margin = 2.5 ∑ + 0.7 σ)

Reference	Margin [mm] LR	Margin [mm] SI	Margin [mm] AP
Current study Interfraction motion	1.8	4.7	4.0
van Herk 2004 [8] Interfraction motion	2.9	5.4	8.6
Soete et al 2007 [13] Interfraction motion	4.4	12.1	12.7
Tanyi et al 2010 [14] Interfraction motion	1.6	8.9	10.2
Tanyi et al 2010 Residual error	2.5	2.6	2.3
Tanyi et al 2010 Intrafraction motion	2.8	3.7	3.2

LR = left-right, SI = superior-inferior, AP = anterior-posterior.

The results of the current study are compared with other published data (Σ = systematic error, σ = ramdom error).