Table 3.
Differences in residual position errors of the landmarks after the described improvements made in the patient setup process (current − previous result, mm). Changes in the van Herk margins (3D) are given in the parenthesis.
| Structure | Systematic error Σ (1 SD) |
Random error σ (1 SD) |
||||
|---|---|---|---|---|---|---|
| AP/vertical | SI/longitudinal | LAT/lateral | AP/vertical | SI/longitudinal | LAT/lateral | |
| Rigid targeta | −0.1 (−0.7) | −0.3 (−0.8) | 0.1 (−0.5) | −0.5c | −0.3 | −0.5c |
| Observer error | −0.3 (−1.0)c | −0.1 (−0.5) | −0.1 (−0.5) | −0.3 | −0.3 | −0.4c |
| C1–2b | −0.9 (−2.6)c | −0.5 (−1.5)c | −0.5 (−1.5)c | −0.6c | −0.3c | −0.4c |
| C5–7b | −0.6 (−1.6)c | −0.4 (−1.5)c | 0.1 (0.0) | −0.2 | −0.6c | −0.3 |
| Mandibleb | −0.9 (−2.5)c | −0.7 (−2.2)c | −0.1 (−0.6) | −0.4 | −0.5c | −0.4c |
| Occiput boneb | −1.0 (−3.1)c | −0.3 (−1.0)c | – | −0.7c | −0.4c | – |
a
For weekly IGRT including inter-observer variation.
b
For daily IGRT including inter-observer variation.
c
The difference is statistically significant (p ≤ 0.05).