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
| 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 |
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.