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Table 3 Patient measurements.

From: Investigation of the usability of conebeam CT data sets for dose calculation

   1F 4F patient plan
Correction strategy 6 MV 18 MV 6 MV 18 MV dose plane DVH
(a) Pelvis Patients       
standard HU-DpCT 21.6% ± 3.7% 15.7% ± 3.4% 14.1% ± 2.1% 10.5% ± 1.7% 8.0% ± 5.7% 19.1% ± 3.4%
phantom based HU-DM20F1 7.7% ± 5.2% 5.6% ± 3.9% 11.2% ± 3.7% 8.4% ± 2.9% 5.2% ± 3.7% 12.7% ± 1.5%
group based HU-DPelvis 2.7% ± 2.3% 2.4% ± 2.0% 2.2% ± 1.9% 1.9% ± 1.5% 0.9% ± 0.9% 1.3% ± 1.0%
patient based HU-DPat_i 2.4% ± 1.7% 2.0% ± 1.4% 1.6% ± 1.3% 1.2% ± 1.1% 0.9% ± 0.9% 1.2% ± 0.9%
(b) Thorax Patients       
standard HU-DpCT 21.6% ± 9.6% 16.4% ± 7.2% 17.1% ± 5.8% 12.6% ± 4.6% 10.9% ± 6.8% 13.8% ± 10.5%
phantom based HU-DM20F1 11.5% ± 7.1% 8.9% ± 5.4% 10.4% ± 4.6% 7.7% ± 3.7% 8.1% ± 3.7% 6.2% ± 4.7%
group based HU-DThorax 4.1% ± 3.5% 3.2% ± 2.8% 3.2% ± 2.2% 2.6% ± 1.9% 1.7% ± 1.7% 1.7% ± 2.4%
patient based HU-DPat_i 4.0% ± 3.4% 3.0% ± 2.7% 2.9% ± 1.9% 2.3% ± 1.7% 1.8% ± 1.6% 1.7% ± 2.0%
(c) Head Patients       
standard HU-DpCT 22.4% ± 10.2% 14.9% ± 9.7% 19.1% ± 4.6% 10.9% ± 5.8% 14.5% ± 10.4% 16.2% ± 12.7%
phantom based HU-DS10F0 3.0% ± 2.7% 2.5% ± 1.0% 2.3% ± 1.9% 2.0% ± 1.7% 1.4% ± 2.4% 1.6% ± 2.2%
group based HU-DHead 2.1% ± 1.7% 2.1% ± 1.5% 1.6% ± 1.4% 1.5% ± 1.5% 1.3% ± 2.3% 1.4% ± 1.9%
patient based HU-DPat_i 2.1% ± 1.7% 1.9% ± 1.5% 1.5% ± 1.3% 1.4% ± 1.4% 1.5% ± 2.5% 1.4% ± 1.9%
  1. Comparison of dose calculation based on planning CT and CBCT with different correction strategies for the different test plans (1F, 4F and IMRT) for (a) pelvis, (b) thorax and (c) head patients. The mean difference between the dose in the planning CT and the CBCT is given in percentage of the dose based on the planning CT. The standard table (HU-DpCT) was generated from CT and density values measured in the planning CT. The phantom based tables HU-DM20F1, HU-DS10F0 were based on the CBCT phantom data sets acquired with collimation M20/bow tie filter and collimation S10/no filter, respectively. The group based tables represent the mean HU-D tables (HU-DPelvis, HU-DThorax, HU-DHead) for the specific patient population (pelvis, thorax, head) while the individual tables (HU-DPat_i) were created based on each patient data set. Dose differences were calculated in volumes of interest for 1F and 4F techniques. For patient plan the dose was compared based on dose planes and dose volume histograms (DVH).