Table 2.
Dosimetric comparison of IMRT, VMAT and TOMO for PTVs in 40 NPC patients.
| Median (IQR) | P-value | |||||||
|---|---|---|---|---|---|---|---|---|
| Target | Index | IMRT | VMAT | TOMO | P | I vs. V | I vs. T | V vs. T |
| PGTVnx | V69.96 (%) | 93.50 (90.00-95.00) | 95.00 (90.25-97.00) | 95.24 (93.59-97.54) | <0.001 | 0.004 | <0.001 | 0.656 |
| D2 (Gy) | 75.77 (74.45-76.36) | 74.37 (73.60-77.36) | 75.38 (74.66-76.23) | 0.273 | _ | _ | _ | |
| D50 (Gy) | 72.64 (72.03-73.02) | 72.21 (71.83-73.15) | 73.30 (72.53-73.73) | 0.023 | 0.438 | 0.596 | 0.018 | |
| D95 (Gy) | 69.56 (68.21-70.03) | 69.90 (67.25-70.34) | 70.02 (69.46-70.48) | <0.001 | 0.016 | <0.001 | 0.221 | |
| D98 (Gy) | 67.81 (63.86-69.11) | 67.73 (62.19-69.63) | 68.80 (66.32-69.74) | <0.001 | 0.281 | <0.001 | 0.057 | |
| CI | 0.435 (0.323-0.498) | 0.445 (0.355-0.500) | 0.474 (0.332-0.525) | 0.026 | 0.221 | 0.03 | 1 | |
| HI | 0.110 (0.080-0.160) | 0.125 (0.060-0.205) | 0.087 (0.078-0.140) | 0.074 | _ | _ | _ | |
| PCTV-1 | V59.4 (%) | 99.00 (98.00-99.00) | 98.50 (97.00-99.00) | 98.96 (98.27-99.62) | 0.581 | _ | _ | _ |
| D2 (Gy) | 75.47 (74.24-76.09) | 74.20 (73.38-76.92) | 75.16 (74.57-76.07) | 0.103 | _ | _ | _ | |
| D50 (Gy) | 71.38 (70.54-72.10) | 71.26 (70.70-72.08) | 71.75 (70.57-72.92) | 0.139 | _ | _ | _ | |
| D95 (Gy) | 62.36 (61.55-63.70) | 62.79 (61.51-63.81) | 62.75 (61.06-63.74) | 0.622 | _ | _ | _ | |
| D98 (Gy) | 60.03 (59.11-61.30) | 60.66 (58.03-61.89) | 60.77 (59.63-61.65) | 0.22 | _ | _ | _ | |
| CI | 0.325 (0.250-0.378) | 0.350 (0.253-0.398) | 0.385 (0.333-0.460) | <0.001 | 0.008 | <0.001 | 0.036 | |
| PCTV-2 | V54 (%) | 98.00 (96.00-98.00) | 97.50 (97.00-99.00) | 98.09 (96.46-98.87) | 0.135 | _ | _ | _ |
| D2 (Gy) | 74.63 (73.47-75.37) | 73.56 (73.00-75.86) | 74.52 (74.21-75.52) | 0.098 | _ | _ | _ | |
| D50 (Gy) | 64.12 (61.90-65.64) | 64.37 (61.88-66.09) | 62.27 (60.16-64.39) | <0.001 | 1 | <0.001 | <0.001 | |
| D95 (Gy) | 55.13 (54.96-55.47) | 55.05 (54.64-55.42) | 55.31 (54.70-55.87) | 0.265 | _ | _ | _ | |
| D98 (Gy) | 55.53 (52.62-54.10) | 53.66 (52.43-54.33) | 54.14 (52.56-54.90) | 0.153 | _ | _ | ||
| CI | 0.690 (0.670-0.748) | 0.760 (0.733-0.803) | 0.730 (0.690-0.770) | <0.001 | <0.001 | 0.005 | 0.009 | |
IMRT/I, intensity modulated radiation therapy; VMAT/V, volumetric modulated arc therapy; TOMO/T, tomotherapy; Gy, gray; IQR, inter-quartile range; DV, the absorbed dose in v% of the volume; CI, conformity index; HI, homogeneity index; Vx, the volume of organ receiving more or equal to x Gy.