The standard deviations of measured deviations Δsij, Δmij, Δtotij around the systematic errors (of each patient j = 1...23) <Δs>j, <Δm>j, <Δtot>j after averaging over i = 1,..., 8 weekly controls provide the random errors sqrt(1/7Σi = 1..8(<Δs>j - Δsij)2), sqrt(1/7Σi = 1..8(<Δmi>j - Δmij)2), sqrt(1/7Σi = 1..8(<Δtoti>j - Δtotij)2) for patient j = 1,..., 23. They are splitted into the RL, SI and AP direction for every error type, i.e. setup error, prostate movement and total error (see Fig. 1 for explanation of symbols). The mean random errors after averaging over 23 patients and their range, i.e. maximum deviations in both orientations of the axes, are given in the table.