Table 3.
Dosimetric parameters and MUs of Δθ = 90° plans, along with their Friedman test results.
| Parameter | Result for VMAT with collimator angles θ1/θ2 a | p-value | |||||
|---|---|---|---|---|---|---|---|
| 280°/10° | 300°/30° | 315°/45° | 330°/60° | 350°/80° | |||
| PTV | CI | 0.859 ± 0.006 | 0.859 ± 0.008 | 0.858 ± 0.007 | 0.855 ± 0.007 | 0.857 ± 0.008 | 0.501 |
| HI | 0.189 ± 0.013 | 0.193 ± 0.013 | 0.189 ± 0.013 | 0.194 ± 0.011 | 0.194 ± 0.019 | 0.289 | |
| Hippocampus | D100% (cGy) | 879.4 ± 34.5 | 873.5 ± 27.1 | 872.2 ± 28.2 | 869.8 ± 31.3 | 878.8 ± 29.2 | 0.112 |
| Dmax (cGy) | 1415.1 ± 71.1 | 1432.9 ± 69.6 | 1411.6 ± 81.8 | 1415.8 ± 65.5 | 1412.7 ± 79.3 | 0.074 | |
| Dmean (cGy) | 1041.7 ± 29.8 | 1045.4 ± 27.5 | 1039.6 ± 31.0 | 1041.6 ± 30.8 | 1043.3 ± 30.3 | 0.412 | |
| Inner ear | Dmean (cGy) | 1411.0 ± 56.0 | 1412.6 ± 31.1 | 1407.8 ± 38.1 | 1403.5 ± 49.4 | 1427.3 ± 29.1 | 0.106 |
| Lens | Dmax (cGy) | 669.3 ± 26.1 | 684.6 ± 20.4 | 683.9 ± 24.5 | 698.5 ± 27.8 | 702.4 ± 38.1 | 0.001* |
| Optical nerve | Dmax (cGy) | 3106.7 ± 87.2 | 3180.2 ± 55.6 | 3180.7 ± 96.1 | 3171.5 ± 63.8 | 3087.3 ± 127.0 | 0.001* |
| Eye | Dmean (cGy) | 919.4 ± 22.8 | 922.8 ± 13.9 | 918.2 ± 21.0 | 925.0 ± 9.4 | 921.0 ± 20.9 | 0.421 |
| Monitor unit | MU | 905.2 ± 37.5 | 878.4 ± 44.4 | 878.5 ± 36.7 | 881.3 ± 36.7 | 899.5 ± 28.2 | 0.003* |
aθ1 and θ2 indicate the collimator angles of arc 1 and arc 2, respectively.
*Statistically significant (p < 0.05).