Table 2.

Interfractional prostate displacement

	AP (mm)	SI (mm)	LR (mm)
Mean	−2.0	2.8	0.2
Minimum	−9.6	−11.2	−3.4
Maximum	6.0	15.4	4.7
Σ	2.0	3.3	0.4
σ	1.6	2.2	0.6

LR = left–right, AP = anterior–posterior, SI = superior–inferior, + = motion to the right/posterior/superior directions about isocenter, Σ = the SD of the average displacement for each individual patient, σ = the root mean square of the individual SD.