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Table 2 Comparison of target volume homogeneity and conformity in all four radiotherapy plan groups

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
PTV72.6 HI 0.07 ± 0.01 0.07 ± 0.01 0.09 ± 0.01 0.09 ± 0.01 <0.001 0.510 <0.001 <0.001 <0.001 <0.001 0.653
CI 0.57 ± 0.09 0.57 ± 0.08 0.49 ± 0.07 0.50 ± 0.07 <0.001 0.955 <0.001 <0.001 <0.001 <0.001 0.355
D2% 75.43 ± 0.76 75.40 ± 0.89 76.30 ± 0.86 76.57 ± 0.66 0.472       
D50% 72.64 ± 0.03 72.68 ± 0.03 72.93 ± 0.11 72.80 ± 0.10 0.588       
D95% 70.55 ± 0.24 70.69 ± 0.30 70.18 ± 0.17 70.10 ± 0.23 0.464       
  D98% 70.01 ± 0.45 70.15 ± 0.57 70.01 ± 0.44 70.02 ± 0.40 0.742       
PTV63.6 HI 0.21 ± 0.02 0.21 ± 0.02 0.23 ± 0.02 0.23 ± 0.02 <0.001 0.427 <0.001 <0.001 <0.001 <0.001 0.614
CI 0.76 ± 0.03 0.76 ± 0.04 0.73 ± 0.03 0.73 ± 0.04 0.001 0.448 0.003 0.001 <0.001 <0.001 0.605
  D2% 72.45 ± 1.11 72.42 ± 1.26 72.89 ± 1.16 73.20 ± 0.79 0.005 0.904 0.174 0.003 0.157 0.002 0.204
  D50% 64.14 ± 0.28 63.64 ± 0.11 63.99 ± 0.19 63.83 ± 0.17 0.236       
  D95% 60.42 ± 0.18 60.44 ± 0.12 60.20 ± 0.17 60.17 ± 0.27 0.715       
  D98% 58.49 ± 0.32 58.83 ± 0.39 57.99 ± 0.50 58.55 ± 0.41 <0.001 0.007 <0.001 0.651 <0.001 0.021 <0.001
  1. HI: homogeneity index; CI: conformity index; GLM-u: general linear model-univariate; VMAT1: single arc VMAT, VMAT2: dual arc VMAT; dIMRT: dynamic MLC IMRT; ssIMRT: step-and-shoot IMRT. “Bold numbers” means that p value has a statistically significance.