Figure 2

Basic definitions of the different error components: The setup error Δs and the motion error Δm can be added to the total error Δtot. For every patient j = 1...23 and portal image i = 1...8 the setup errors Δs_ij are determined by matching the bony contours of the portal images (i, j) to the reference images j (simulator radiographs) according Figure 1. The motion errors Δm_ij are determined after these matching procedures by subtracting the marker positions of the matched portal images (i, j) and the reference images j. The systematic error for a patient j is defined as the mean of single errors with respect to i = 1...8 portal images. The random error of patient j is defined as the standard deviation of this series. Then further statistical evaluation is possible, e.g. the mean systematic error for a series of patients (here 23 patients) in Table 2 and the mean standard deviations (mean random error) in Table 3.