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Table 1 Systematic and random translational errors for conventional positioning with skin marks (laser crosses), infrared body markers and bone fusion (via ExacTrac/Novalis Body X-ray system = ETNB) by using the marker-based prostate position as “correct” reference position

From: Appropriate patient instructions can reduce prostate motion

Setup LR error [mm] SI error [mm] AP error [mm]
Skin marks    
Σ 1.56 2.46 1.87
σ 1.82 2.31 2.51
Margin 5.17 7.76 6.43
Infrared markers    
Σ 1.35 0.75 0.96
σ 1.73 1.10 1.71
Margin 4.59 2.64 3.60
Bone fusion (ETNB)    
Σ 0.53 1.38 1.10
σ 0.75 1.84 1.79
Margin 1.85 4.74 4.00
  1. The recommended safety margins according to the formula of van Herk (margin = 2.5 ∑ + 0.7 σ, see text) along the three axes are given in the third line.