Potentials of on-line repositioning based on implanted fiducial markers and electronic portal imaging in prostate cancer radiotherapy

Table 2 Systematic errors

	Mean ± SD [mm] j = 1,..., 23	Range [mm] j = 1,..., 23
Systematic setup error <Δs>_j
Left-right	0.8 ± 1.6	-2.9/3.9
Superior-inferior	0.1 ± 2.1	-2.7/6.2
Anterior-posterior	-1.2 ± 2.4	-5/4.1
Systematic prostate movement <Δm>_j
Left-right	-0.3 ± 1.1	-2.9/2.7
Superior-inferior	0.9 ± 1.9	-3.1/4.7
Anterior-posterior	0.3 ± 2.3	-4.3/5.0
Systematic total error <Δtot>_j
Left-right	0.5 ± 2.0	-2.6/6.6
Superior-inferior	0.9 ± 2.7	-4.3/7.3
Anterior-posterior	-0.8 ± 2.6	-6.7/4.0

Analysis of the mean vectorial setup errors per patient (after averaging over i = 1,..., 8 weekly controls) (1/8)Σ_{i = 1...8} Δs_ij =: <Δs>_j, the mean vectorial prostate movements (1/8)Σ_{i = 1...8} Δm_ij =: <Δm>_j and the mean vectorial total errors (1/8)Σ_{i = 1...8} Δtot_ij =: <Δtot>_j. After statistical analysis with respect to j = 1 to 23 patients we achieve the population based (mean) vectorial systematic error defined as (1/23)Σ_{j = 1...23}<Δs>_j, (1/23)Σ_{j = 1...23}<Δm>_j and (1/23)Σ_{j = 1...23}<Δtot>_j splitted in the RL, SI and AP direction and the standard deviation SD from these errors (see Fig. 2 for explanation of symbols). Also the range (minimum to maximum) is listed (right row).

ISSN: 1748-717X