Background
Methods
Validation of the fine resolution MLC simulation by CT image shift method
Patient selection and simulation
Generation of original VMAT plans
Structure | Initial dose volume constraints | Relative priority |
---|---|---|
Primary plan | ||
Primary PTV | D100% ≥ 99.5 % of the prescription dose | 150 |
D98% ≥ 100 % of the prescription dose | 150 | |
D2% ≤ 101 % of the prescription dose | 150 | |
Dmax ≤ 102 % of the prescription dose | 150 | |
Rectal wall | V44Gy ≤ 20 % | 100 |
V30Gy ≤ 50 % | 100 | |
Bladder | V44Gy ≤ 20 % | 100 |
V30Gy ≤ 50 % | 100 | |
Femoral heads | V23Gy ≤ 50 % | 80 |
Boost plan | ||
Boost PTV | D100% ≥ 99.5 % of the prescription dose | 150 |
D98% ≥ 100 % of the prescription dose | 150 | |
D2% ≤ 101 % of the prescription dose | 150 | |
Dmax ≤ 102 % of the prescription dose | 150 | |
Rectal wall | V22Gy ≤ 20 % | 100 |
V18Gy ≤ 50 % | 100 | |
Bladder | V22Gy ≤ 20 % | 100 |
V18Gy ≤ 50 % | 100 | |
Femoral heads | V12Gy ≤ 50 % | 80 |
Simulation of VMAT plans using MLCs with 1.25 mm leaf width (generation of shifted VMAT plans)
Evaluation of dosimetric changes in the shifted VMAT plans compared to the original VMAT plans
Results
Validation of the fine resolution MLC simulation by the shift method
Differences in dose-volumetric parameters between original and shifted primary VMAT plans
Original plan | Shifted plan |
p
| |
---|---|---|---|
Primary target volume | |||
D1% (Gy) | 51.99 ± 0.36 | 51.71 ± 0.31 |
<0.001
|
Mean dose (Gy) | 50.70 ± 0.22 | 50.50 ± 0.20 |
0.007
|
D99% (Gy) | 47.87 ± 0.36 | 47.94 ± 0.32 |
0.026
|
D95% (Gy) | 49.33 ± 0.08 | 49.30 ± 0.07 | 0.107 |
D5% (Gy) | 51.58 ± 0.33 | 51.32 ± 0.31 |
0.014
|
V95% (%) | 99.07 ± 0.36 | 99.15 ± 0.35 | 0.478 |
Conformity index | 1.06 ± 0.05 | 1.04 ± 0.04 |
0.006
|
Homogeneity index | 0.07 ± 0.01 | 0.06 ± 0.01 |
<0.001
|
Normal tissue | |||
Gradient measure (cm) | 1.86 ± 0.18 | 2.01 ± 0.26 |
0.041
|
Monitor Unit (MU) | |||
MU | 532 ± 115 | 572 ± 117 | 0.294 |
Differences in dose-volumetric parameters between original and shifted boost VMAT plans
Original plan | Shifted plan |
p
| |
---|---|---|---|
Boost target volume | |||
D1% (Gy) | 31.43 ± 0.24 | 31.26 ± 0.31 |
<0.001
|
Mean dose (Gy) | 30.71 ± 0.17 | 30.57 ± 0.17 |
0.015
|
D99% (Gy) | 29.18 ± 0.10 | 29.25 ± 0.09 |
0.001
|
D95% (Gy) | 29.92 ± 0.05 | 29.89 ± 0.04 | 0.095 |
D5% (Gy) | 31.20 ± 0.22 | 31.02 ± 0.24 |
0.015
|
V95% (%) | 99.24 ± 0.22 | 99.38 ± 0.21 |
0.039
|
Conformity index | 1.02 ± 0.02 | 1.01 ± 0.02 |
<0.001
|
Homogeneity index | 0.06 ± 0.01 | 0.05 ± 0.01 |
<0.001
|
Normal tissue | |||
Gradient measure (cm) | 1.66 ± 0.26 | 1.94 ± 0.47 |
0.027
|
Monitor Unit (MU) | |||
MU | 470 ± 59 | 495 ± 61 | 0.219 |
Differences in dose-volumetric parameters between original and shifted sum VMAT plans
Original plan | Shifted plan |
p
| |
---|---|---|---|
Boost target volume | |||
D1% (Gy) | 83.00 ± 0.39 | 82.55 ± 0.34 |
<0.001
|
Mean dose (Gy) | 81.45 ± 0.32 | 81.12 ± 0.28 |
0.001
|
D99% (Gy) | 77.98 ± 0.44 | 78.11 ± 0.37 |
0.014
|
D95% (Gy) | 79.76 ± 0.33 | 79.68 ± 0.29 | 0.411 |
Primary target volume | |||
Mean dose (Gy) | 77.33 ± 2.22 | 77.04 ± 2.25 | 0.681 |
D99% (Gy) | 55.11 ± 4.17 | 55.01 ± 4.23 | 0.267 |
D95% (Gy) | 59.42 ± 6.27 | 59.16 ± 6.32 | 0.896 |
Rectal wall | |||
V70Gy (%) | 10.56 ± 3.08 | 10.38 ± 3.08 | 0.856 |
V47Gy (%) | 32.40 ± 10.04 | 31.21 ± 9.51 | 0.700 |
D50% (Gy) | 32.18 ± 11.35 | 31.22 ± 11.43 | 0.791 |
Mean dose (Gy) | 36.68 ± 7.05 | 36.06 ± 6.97 | 0.783 |
Bladder | |||
V70Gy (%) | 6.44 ± 4.42 | 6.37 ± 4.36 | 0.958 |
V47Gy (%) | 14.35 ± 8.62 | 14.19 ± 8.51 | 0.954 |
D50% (Gy) | 12.58 ± 10.11 | 12.39 ± 10.00 | 0.952 |
Mean dose (Gy) | 20.62 ± 9.52 | 20.43 ± 9.46 | 0.949 |
Right femoral head | |||
D50% (Gy) | 15.09 ± 2.31 | 14.88 ± 2.39 | 0.786 |
Maximum dose (Gy) | 27.51 ± 4.10 | 27.54 ± 4.44 | 0.981 |
Left femoral head | |||
D50% (Gy) | 15.01 ± 3.55 | 14.79 ± 3.51 | 0.846 |
Maximum dose (Gy) | 26.68 ± 3.62 | 27.34 ± 4.65 | 0.618 |
Whole body including target volume | |||
V81Gy (cc) | 60.92 ± 14.85 | 48.96 ± 11.68 |
0.007
|
Body – primary target volume | |||
V81Gy (cc) | 0.12 ± 0.13 | 0.07 ± 0.08 | 0.083 |
V72.9Gy (cc) | 19.23 ± 4.74 | 18.77 ± 4.59 | 0.074 |
V64.8Gy (cc) | 43.53 ± 9.61 | 43.08 ± 9.65 | 0.290 |
V50.4Gy (cc) | 117.78 ± 23.83 | 117.06 ± 24.26 | 0.222 |
V45.36Gy (cc) | 163.60 ± 31.56 | 163.02 ± 32.28 | 0.359 |
V40.32Gy (cc) | 226.73 ± 42.88 | 226.39 ± 44.16 | 0.707 |
V8.1Gy (cc) | 2963.81 ± 366.10 | 2979.18 ± 366.93 | 0.072 |