Table 3.
Dosimetric comparison of IMRT, VMAT and TOMO for organs at risk (priority level I and II) in 40 NPC patients.
| Median (IQR) | P-value | |||||||
|---|---|---|---|---|---|---|---|---|
| OAR | Objective | IMRT | VMAT | TOMO | P | I vs. V | I vs. T | V vs. T |
| Brain stem | Dmax (Gy) | 53.13 (49.23-55.29) | 53.74 (49.24-57.16) | 51.74 (44.74-54.34) | <0.001 | 0.791 | 0.016 | <0.001 |
| Brain stem_PRV | D0.03cc (Gy) | 56.50 (52.31-60.34) | 58.18 (52.78-62.96) | 58.67 (54.19-63.31) | 0.407 | _ | _ | _ |
| Optic chiasm | Dmax (Gy) | 27.51 (10.24-45.85) | 27.88 (10.03-44.05) | 31.86 (20.90-45.82) | 0.004 | 1 | 0.03 | 0.005 |
| Optic chiasma_PRV | D0.03cc (Gy) | 36.77 (18.73-53.54) | 41.40 (18.39-51.75) | 41.67 (28.14-54.36) | <0.001 | 0.353 | 0.03 | <0.001 |
| Optic nerve_L | Dmax (Gy) | 16.25 (7.87-38.55) | 19.41 (7.72-37.70) | 29.17 (18.35-42.68) | <0.001 | 1 | <0.001 | <0.001 |
| Optic nerve_L PRV | D0.03cc (Gy) | 26.87 (12.27-46.83) | 30.73 (13.24-50.25) | 35.87 (25.45-52.81) | <0.001 | 0.943 | 0.001 | <0.001 |
| Optic nerve_R | Dmax (Gy) | 17.08 (8.07-40.61) | 19.46 (7.83-39.03) | 32.86 (18.12-44.37) | <0.001 | 1 | 0.002 | 0.001 |
| Optic nerve_R PRV | D0.03cc (Gy) | 31.22 (13.11-48.98) | 30.32 (13.07-50.97) | 41.74 (26.82-53.22) | <0.001 | 0.353 | 0.03 | <0.001 |
| Spinal cord | Dmax (Gy) | 39.12 (37.99-40.36) | 40.29 (38.20-41.98) | 35.57 (32.48-38.20) | <0.001 | 0.101 | <0.001 | <0.001 |
| Spinal cord_PRV | D0.03cc (Gy) | 44.12 (42.13-47.48) | 44.46 (43.00-48.08) | 43.31 (40.16-49.35) | 0.163 | _ | _ | _ |
| Temporal lobe_L | Dmax (Gy) | 73.73 (64.63-77.21) | 73.16 (66.83-78.16) | 72.10 (64.34-75.94) | <0.001 | 1 | <0.001 | <0.001 |
| Temporal lobe_L PRV | D0.03cc (Gy) | 75.25 (71.47-77.00) | 74.77 (71.69-78.34) | 73.63 (69.29-75.95) | <0.001 | 1 | <0.001 | <0.001 |
| Temporal lobe_R | Dmax (Gy) | 75.74 (67.58-77.54) | 74.30 (68.85-77.92) | 73.27 (64.84-75.84) | <0.001 | 1 | <0.001 | <0.001 |
| Temporal lobe_R PRV | D0.03cc (Gy) | 76.34 (72.47-77.60) | 75.06 (72.20-79.19) | 74.34 (71.68-75.64) | 0.001 | 1 | 0.002 | 0.009 |
IMRT/I, intensity modulated radiation therapy; VMAT/V, volumetric modulated arc therapy; TOMO/T, tomotherapy; OAR, organ at risk; IQR, inter-quartile range; Gy, gray; PRV, planning risk volume; L, left; R, right; Dmax, the maximum dose; D0.03cc, an approximate maximum dose for the organs at risk.