Table 1.
Mean, standard deviation and median for 150 registrations using different rendering thresholds for DRR generation. Both the mTRE—based on the evaluation of 400 known positions inside the CT volume—and the mean error in the projected positions (mean projected distance mPD) were recorded. The upper rows give the mean and standard deviation, whereas the median is given in the lower row. RC generally provides the lowest results with the lowest scatter as indicated by the standard deviation, and appears to be the measure most robust against differences in image intensities which were introduced by changing the rendering threshold. The best values for mTRE and mPD are printed in boldface in each column.
| Threshold (HU) | CC | RC | SRC 5% | CR | MI | |
|---|---|---|---|---|---|---|
| mPD (mm) |
−868 |
2.96 ± 1.25 2.74 |
3.08 ± 2.62 2.66 |
3.82 ± 3.31 3.11 |
7.68 ± 4.65 6.45 |
3.88 ± 1.09 3.73 |
| −711 | 4.60 ± 2.38 4.01 |
2.50 ± 0.76 2.38 |
2.67 ± 1.52 2.16 |
2.00 ± 1.90 1.49 |
3.27 ± 2.03 2.86 |
|
| −555 | 4.79 ± 3.26 3.91 |
2.68 ± 0.43 2.62 |
3.12 ± 2.23 2.52 |
2.71 ± 2.57 1.52 |
3.36 ± 1.74 2.96 |
|
| −400 | 6.02 ± 4.55 4.38 |
3.02 ± 1.34 2.87 |
3.86 ± 2.89 3.22 |
2.54 ± 2.18 1.62 |
4.21 ± 2.35 3.51 |
|
| −243 | 14.05 ± 2.19 13.48 |
6.65 ± 8.11 4.3 |
6.84 ± 6.19 5.17 |
8.07 ± 4.90 6.67 |
15.38 ± 5.88 12.91 |
|
| mTRE (mm) |
−868 | 4.16 ± 2.84 2.93 |
4.04 ± 3.07 2.95 |
4.48 ± 3.45 3.20 |
6.55 ± 2.90 5.80 |
5.64 ± 2.90 4.72 |
| −711 | 5.09 ± 3.07 3.92 |
3.27 ± 2.52 2.66 |
3.77 ± 2.62 2.68 |
3.56 ± 3.11 2.18 |
4.29 ± 2.71 3.44 |
|
| −555 | 5.79 ± 4.27 3.85 |
3.69 ± 2.35 2.80 |
4.01 ± 2.97 2.87 |
3.80 ± 2.92 2.76 |
4.33 ± 2.98 3.39 |
|
| −400 | 6.80 ± 5.28 4.27 |
4.03 ± 2.51 2.90 |
4.34 ± 3.28 3.33 |
3.86 ± 2.95 2.93 |
5.13 ± 3.91 3.73 |
|
| −243 | 13.77 ± 1.80 13.15 |
6.94 ± 7.70 4.22 |
7.02 ± 5.93 5.03 |
8.10 ± 4.39 6.56 |
15.27 ± 5.63 12.76 |