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Table 3 Dosimetric comparison of normal tissues in all four radiotherapy plan groups (Gy)

From: Single arc volumetric-modulated arc therapy is sufficient for nasopharyngeal carcinoma: a dosimetric comparison with dual arc VMAT and dynamic MLC and step-and-shoot intensity-modulated radiotherapy

  VMAT1 VMAT2 dIMRT ssIMRT p GLM-u p VMAT1 p VMAT1 p VMAT1 p VMAT2 p VMAT2 p dIMRT
      -VMAT2 -dIMRT -ssIMRT -dIMRT -ssIMRT -ssIMRT
Brain stem D2% 41.21 ± 0.92 41.94 ± 0.42 42.56 ± 0.48 46.32 ± 0.44 0.024 0.679 0.444 0.005 0.724 0.015 0.036
Dmean 24.02 ± 2.58 23.46 ± 3.97 24.85 ± 3.86 27.51 ± 0.41 <0.001 0.326 0.056 <0.001 0.117 <0.001 <0.001
Spinal-cord D2% 35.15 ± 1.75 32.59 ± 2.91 33.60 ± 2.67 28.66 ± 3.02 <0.001 0.001 0.073 <0.001 0.160 <0.001 <0.001
Dmean 26.26 ± 2.66 23.46 ± 2.74 25.01 ± 2.79 22.3 ± 3.52 <0.001 <0.001 0.055 <0.001 0.017 0.071 0.001
Chiasm Dmax 47.51 ± 4.52 47.89 ± 5.01 47.17 ± 5.83 48.23 ± 6.32 0.600       
Dmean 34.44 ± 6.88 36.38 ± 5.79 35.30 ± 5.46 36.37 ± 7.30 0.013 0.033 0.427 0.023 0.330 0.988 0.337
Optic N L Dmax 43.73 ± 10.41 46.20 ± 9.77 44.13 ± 9.52 45.11 ± 10.00 0.177       
Dmean 24.17 ± 9.69 26.17 ± 9.69 24.40 ± 8.29 26.22 ± 9.24 0.022 0.021 0.787 0.018 0.07 0.955 0.065
Optic N R Dmax 43.30 ± 11.85 44.88 ± 9.57 42.04 ± 10.18 44.84 ± 8.91 0.048 0.177 0.278 0.188 0.017 0.971 0.018
Dmean 25.04 ± 9.69 25.66 ± 9.53 23.92 ± 8.74 26.04 ± 9.15 0.076       
Lens L Dmean 3.86 ± 1.35 4.13 ± 1.49 4.18 ± 1.38 5.18 ± 1.53 <0.001 0.111 0.06 <0.001 0.767 <0.001 <0.001
Lens R Dmean 3.71 ± 1.05 4.35 ± 1.7 4.21 ± 1.21 5.22 ± 1.38 <0.001 0.004 0.022 <0.001 0.535 <0.001 <0.001
Parotid L D50% 28.45 ± 4.20 27.04 ± 4.99 23.89 ± 4.05 26.73 ± 4.09 <0.001 0.064 <0.001 0.025 <0.001 0.682 <0.001
Dmean 32.20 ± 3.30 31.57 ± 3.86 29.01 ± 3.31 31.48 ± 3.21 <0.001 0.223 <0.001 0.165 <0.001 0.863 <0.001
Parotid R D50% 31.73 ± 5.88 28.18 ± 5.38 25.42 ± 5.53 27.07 ± 3.79 <0.001 0.001 <0.001 <0.001 0.008 0.273 0.104
Dmean 34.14 ± 3.56 32.47 ± 3.83 30.11 ± 3.93 31.65 ± 3.08 <0.001 0.085 <0.001 0.001 0.001 0.238 0.097
Oral cavity Dmean 40.35 ± 4.77 36.99 ± 6.18 41.42 ± 6.77 43.21 ± 5.60 <0.001 <0.001 0.230 0.002 <0.001 <0.001 0.049
Larynx Dmean 37.67 ± 4.13 35.17 ± 4.55 35.86 ± 3.05 34.76 ± 3.82 <0.001 0.001 0.003 <0.001 0.249 0.395 0.048
  1. GLM-u: general linear model-univariate; VMAT1: single arc VMAT, VMAT2: dual arc VMAT; dIMRT: dynamic MLC IMRT; ssIMRT: step-and-shoot IMRT. Lens L, left lens; Lens R, right lens; Optic L, left optic nerve; Optic R, right optic nerve; Parotid L, left parotid; Parotid R, right parotid. “Bold numbers” means that p value has a statistically significance.