Table 3.
Dosimetric comparison of VMAT and IMRT for the organs at risk (OARs) (
)
| OARs | Index | VMAT (cGy) | IMRT (cGy) | P |
|---|---|---|---|---|
| All (n=80) | ||||
| Brain Stem | Dmax | 5879±555 | 5532±575 | 0.007 |
| Spinal Cord | Dmax | 4123±327 | 3766±221 | <0.001 |
| Temporal Lobe _L | Dmax | 6796±483 | 6704±548 | 0.428 |
| Temporal Lobe _R | Dmax | 6741±462 | 6812±569 | 0.541 |
| Pituitary | Dmax | 5872±810 | 5546±1115 | 0.139 |
| Optic Chiasm | Dmax | 4319±1682 | 3925±1886 | 0.327 |
| Optic Nerves _L | Dmax | 3550±1867 | 2545±1918 | 0.020 |
| Optic Nerves _R | Dmax | 3668±1901 | 2707±2031 | 0.032 |
| Lens _L | Dmax | 527±247 | 455±208 | 0.160 |
| Lens _R | Dmax | 575±314 | 470±248 | 0.101 |
| Inner ear _L | Dmean | 4437±967 | 4379±548 | 0.743 |
| Inner ear _R | Dmean | 4156±965 | 4530±692 | 0.050 |
| TM Joint _L | Dmean | 4084±771 | 3848±527 | 0.115 |
| TM Joint _R | Dmean | 4193±828 | 4006±689 | 0.277 |
| Mandible _L | Dmean | 4039±495 | 4050±405 | 0.916 |
| Mandible _R | Dmean | 4037±543 | 4119±427 | 0.458 |
| Parotid _L | Dmean | 3747±527 | 3841±609 | 0.464 |
| Parotid _R | Dmean | 3880±648 | 3861±384 | 0.873 |
| T1-2 (n=52) | ||||
| Brain Stem | Dmax | 5614±371 | 5322±397 | 0.008 |
| Spinal Cord | Dmax | 4081±354 | 3774±228 | 0.001 |
| Optic Nerves _L | Dmax | 2738±1675 | 2134±1689 | 0.201 |
| Optic Nerves _R | Dmax | 2887±1730 | 2185±1685 | 0.144 |
| T3-4 (n=28) | ||||
| Brain Stem | Dmax | 6372±507 | 5923±659 | 0.054 |
| Spinal Cord | Dmax | 4201±263 | 3750±217 | <0.001 |
| Optic Nerves _L | Dmax | 5057±1138 | 3309±2141 | 0.014 |
| Optic Nerves _R | Dmax | 5117±1269 | 3678±2315 | 0.055 |
Abbreviations: VMAT, volumetric modulated arc therapy; IMRT, intensity modulated radiation therapy; OAR, organ at risk; cGy, centigray; T, T stage; L, left; R, right; Dmax, the maximun dose; Dmean, the mean dose.