Fig 1.
Comparison of (a) percentage depth dose (PDD) curves and (b) lateral dose profiles at 5 cm depth for field sizes of 3×3 cm2, 10×10 cm2 and 20×20 cm2 between Monte Carlo simulated (solid lines) and Pinnacle3 calculation results (dashed lines) for the 3-MV photon beam at 100 cm source-to-surface distance.
The deviations in depth doses were shown in the lower part to the right scale.
Fig 2.
Comparison of Pinnacle3 calculated and Monte Carlo simulated dose profiles of 6-MV (a,c) and 3-MV (b, d) beam along the line for two MLC shaped fields (inserts, not to the scale) at 5 and 10 cm depths of a homogeneous water phantom.
All doses were normalized to the central axis at 5 cm depth for comparison.
Fig 3.
Comparison of Pinnacle3 calculated and Monte Carlo simulated percentage depth dose (a, b) and profiles (c, d) of 6-MV and 3-MV beam under inhomogeneous condition.
A lung block of 5 cm thick, with a density of 0.3 g/cm3 was inserted in a water phantom from 5 cm depth, while the lateral dimensions were either 15×15 cm2 or 15×7.5 cm2. The field sizes were 3×3 cm2 and 5×5 cm2.
Table 1.
Summary of patient characteristics.
Table 2.
Guidelines of dose volume constraints for the organs-at-risk (OARs)
Fig 4.
The dose distributions (a) and dose-volume histograms (DVHs) (b) of a representative case.
(a) From left to right: 6-MV, 3-MV and the dual energy plans. From top to bottom: axial: sagittal, and coronal views. The isodose lines are 120% (purple), 105% (yellow), 100% (pink), 95% (light blue), 70% (green), 50% (orange), 40% (steel blue) and 20% (dark blue). Notable differences are marked by red arrows. (b) The 6-MV, 3-MV and dual energy plans are shown with thick lines, dashed lines and thin lines, respectively. The DVH curves for trachea, esophagus and skin are not shown due to very low dose level.
Table 3.
Dosimetric comparison of tumor target coverage.
Fig 5.
The percentage dosimetric differences for the lung (a), cord (b), esophagus (c), trachea (d), and the heart (e).
The percentage difference was calculated as . Each patient is illustrated by a red symbol (left) for 3-MV and green one (right) for dual energy plan. The mean difference of each index for the whole group is marked with a cross x.
Fig 6.
Dosimetric comparisons of lung and spinal cord.
All parameters were normalized to the counterparts of 6-MV plan shown as the solid black line. Patients were categorized into short effective path length (SEP, < 10 cm) and Long effective path length (LEP, > 10 cm) groups.
Fig 7.
Comparison of integral dose for three plans.
Individual patients were represented with the average effective path length (AEP) and categorzed into two groups (short effective path legnth (SEP) and long effective path legnth (LEP)). Integral doses were calcuated as DmeanBody × VBody − DmeanPTV × VPTV and normalized to 6-MV plans.
Fig 8.
Comparison of Beam-On-Time for three plans.
Individual patients were represented with the average effective path length (AEP) and categorized into two groups (short effective path legnth (SEP) and long effective path legnth (LEP)).