Table 3.
Mean dose parameters in GyE for OARs in 8 NPC patients planned with IMPT and IMRT
| Organ/ | IMPT | IMRT | IMPT/IMRT | P value |
| Parameter | Mean (Range) | Mean (Range) | Mean dose ratio | |
| Optic chiasm | ||||
| D. max | 16.1 (0.0 – 52.3) | 23.8 (4.8 – 56.8) | 0.67 | 0.008 |
| Spinal cord | ||||
| D. max | 16.7 (10.1 – 28.7) | 46.0 (44.0 – 50.0) | 0.36 | 0.008 |
| Brainstem | ||||
| D. max | 47.3 (14.6 – 60.5) | 58.7 (53.6 – 64.2) | 0.80 | 0.055 |
| Temp. lobe | ||||
| D. max | 57.2 (33.0 – 67.8) | 61.8 (53.5 – 67.7) | 0.92 | 0.021 |
| D. mean | 5.4 (0.5 – 12.3) | 13.4 (8.4 – 20.3) | 0.40 | < 0.0001 |
| Inner ear | ||||
| D. max | 36.3 (8.0 – 76.1) | 51.8 (32.8 – 73.0) | 0.70 | 0.009 |
| D. mean | 13.1 (1.1 – 43.9) | 36.4 (21.8 – 53.0) | 0.36 | < 0.0001 |
| Mid/ext ear | ||||
| D. max | 37.4 (8.0 – 70.4) | 49.2 (33.0 – 68.2) | 0.76 | 0.039 |
| D. mean | 8.1 (0.3 – 13.5) | 24.5 (19.4 – 32.8) | 0.33 | < 0.0001 |
| TM joint | ||||
| D. max | 54.9 (37.0 – 73.0) | 60.5 (45.9 – 71.4) | 0.90 | 0.252 |
| D. mean | 17.4 (7.3 – 28.9) | 38.8 (27.9 – 54.6) | 0.44 | < 0.0001 |
| Larynx/esophgus | ||||
| D. max | 52.8 (46.6 – 64.4) | 57.9 (52.3 – 64.1) | 0.91 | 0.039 |
| D. mean | 14.3 (8.6 – 18.5) | 30.6 (24.3 – 35.3) | 0.46 | 0.008 |
| Oral cavity | ||||
| D. max | 70.2 (68.6 – 73.9) | 72.1 (70.4 – 74.4) | 0.97 | 0.055 |
| D. mean | 38.1 (33.9 – 43.7) | 44.0 (40.5 – 46.7) | 0.86 | 0.016 |
| Pituitary gl. | ||||
| D. max | 44.9 (3.2 – 73.0) | 53.5 (20.6 – 73.8) | 0.84 | 0.055 |
| D. mean | 34.8 (1.1 – 71.0) | 42.2 (11.6 – 65.9) | 0.82 | 0.148 |
| Thyroid gl. | ||||
| D. max | 51.5 (42.4 – 64.2) | 57.5 (52.9 – 64.9) | 0.89 | 0.008 |
| D. mean | 19.8 (12.5 – 24.4) | 38.2 (33.7 – 45.4) | 0.52 | 0.008 |
| Parotid gl. | ||||
| D. mean | 36.3 (23.6 – 44.3) | 40.0 (26.0 – 49.0) | 0.91 | 0.011 |
GyE = cobalt Gray equivalent, TM = temporomandibular, Mid/ext = middle/external. D. max is the absolute maximal dose in a single voxel.