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Table 2 Volume and dose changes of target and parotid gland

From: Rules of parotid gland dose variations and shift during intensity modulated radiation therapy for nasopharyngeal carcinoma

  The first 15 fractions Between fraction 15 and 25
  SCT-1 vs. SCT-2 SCT-2 vs. SCT-3
Volume changes Mean ± SD 95% CI p Value Mean ± SD 95% CI p Value
GTVnx 8.23 ± 13.61 4.24; 12.24 0.000 3.30 ± 8.09 0.92; 5.67 0.008
GTVnd 10.27 ± 13.37 6.02; 14.51 0.000 4.88 ± 8.41 2.19; 7.57 0.001
L-PG 2.06 ± 2.99 1.19; 2.94 0.000 5.90 ± 2.99 5.02; 6.78 0.000
R-PG 2.46 ± 4.50 1.14; 3.78 0.000 4.68 ± 3.23 3.74; 5.63 0.000
CON-PG 2.98 ± 3.50 1.80; 4.17 0.000 5.78 ± 3.00 4.77; 6.80 0.000
IP-PG 1.81 ± 3.94 0.78; 2.85 0.001 4.99 ± 3.23 4.14; 5.84 0.000
Dose changes Plan 1 vs. Plan 2 Plan 3 vs. Plan 4
(PG V30) Mean ± SD 95% CI p Value Mean ± SD 95% CI p Value
L-PG −6.87 ± 15.58 −11.45; −2.29 0.004 −0.81 ± 15.94 −5.49; 3.87 0.728
R-PG −5.61 ± 16.04 −10.32; −0.90 0.021 −1.14 ± 21.54 −7.46; 5.19 0.719
CON-PG −3.41 ± 13.44 −8.18; 1.36 0.155 0.25 ± 21.61 −7.42; 7.91 0.948
IP-PG −7.77 ± 16.76 −12.06; −3.48 0.001 −1.64 ± 17.33 −6.07; 2.80 0.464
  1. Abbreviations: SD standard deviation, CI confindence interval, R-PG the right parotid gland, L-PG the left parotid gland, GTVnx the gross tumor volume of the nasopharynx, GTVnd the cervical lymph node, Con-PG contralateral parotid gland, IP-PG ipsilateral parotid gland, V30 the percentage of parotid gland volume receiving ≥ 30Gy, SCT-1 the first simulation CT scan before treatment, SCT-2 the second simulation CT scan at the fifteenth fraction of treatment, SCT-3 the third simulation CT scan at the twenty-fifth fraction of treatment, Plan 1 the initial IMRT plan generated based on the SCT-1, Plan 2 was made by applying the beam configurations of Plan 1 to SCT-2, Plan 3 the re-IMRT plan on the SCT-2, Plan 4 was made by applying the beam configurations of Plan 3 to SCT-3.