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Table 5 Dosimetric comparison of plans with pre-correction margins and plans with post-correction margins for the PTVs in 40 NPC patients

From: Dosimetric benefit to organs at risk following margin reductions in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy

Target Dose index Plan with pre-correction margins Plan with post-correction margins Difference P value
PTV_7000 D2% (Gy) 76.2 ± 0.84 75.97 ± 0.79 0.28 ± 0.57 0.003
  D50% (Gy) 73.79 ± 0.43 73.59 ± 0.38 0.19 ± 0.32 <0.001
  D95% (Gy) 71.05 ± 0.32 71.06 ± 0.26 −0.01 ± 0.16 0.738
  D98% (Gy) 69.53 ± 1.34 69.80 ± 1.01 −0.27 ± 0.44 <0.001
  HI 0.09 ± 0.03 0.08 ± 0.02 0.01 ± 0.01 <0.001
PTV_6000 D2% (Gy) 75.77 ± 0.85 75.44 ± 0.80 0.33 ± 0.48 <0.001
  D50% (Gy) 71.18 ± 1.29 70.79 ± 1.22 0.39 ± 0.30 <0.001
  D95% (Gy) 64.00 ± 1.06 63.85 ± 1.06 0.16 ± 0.44 0.030
  D98% (Gy) 62.33 ± 1.04 62.34 ± 1.07 −0.02 ± 0.45 0.805
  HI 0.19 ± 0.02 0.18 ± 0.02 0.01 ± 0.01 0.010
PTV_5600 D2% (Gy) 74.60 ± 1.04 74.33 ± 1.06 0.27 ± 0.38 <0.001
  D50% (Gy) 62.58 ± 0.77 62.41 ± 0.83 0.17 ± 0.40 0.009
  D95% (Gy) 57.81 ± 0.56 57.72 ± 0.54 0.09 ± 0.22 0.018
  D98% (Gy) 55.69 ± 1.06 55.70 ± 1.08 −0.01 ± 0.35 0.990
  HI 0.30 ± 0.03 0.29 ± 0.03 0.01 ± 0.01 0.002
  1. All data are presented as mean ± SD of 40 patients. HI, homogeneity index; D2%, dose received by 2% of the volume; D50%, dose received by 50% of the volume; D95%, dose received by 95% of the volume; D98%, dose received by 98% of the volume. Other abbreviations as in Tables 3 and 4.