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Abstract
Acuros XB advanced dose calculation algorithm (AXB, Varian Medical Systems, Palo Alto, CA) has been released recently and provided the advantages of speed and accuracy for dose calculation. For clinical use, it is important to investigate the dosimetric performance of AXB compared to the calculation algorithm of the previous version, Anisotropic Analytical Algorithm (AAA, Varian Medical Systems, Palo Alto, CA). Ten volumetric modulated arc therapy (VMAT) plans for each of the following cases were included: head and neck (H&N), prostate, spine, and lung. The spine and lung cases were treated with stereotactic body radiation therapy (SBRT) technique. For all cases, the dose distributions were calculated using AAA and two dose reporting modes in AXB (dose-to-water, AXBw, and dose-to-medium, AXBm) with same plan parameters. For dosimetric evaluation, the dose-volumetric parameters were calculated for each planning target volume (PTV) and interested normal organs. The differences between AAA and AXB were statistically calculated with paired t-test. As a general trend, AXBw and AXBm showed dose underestimation as compared with AAA, which did not exceed within −3.5% and −4.5%, respectively. The maximum dose of PTV calculated by AXBw and AXBm was tended to be overestimated with the relative dose difference ranged from 1.6% to 4.6% for all cases. The absolute mean values of the relative dose differences were 1.1±1.2% and 2.0±1.2% when comparing between AAA and AXBw, and AAA and AXBm, respectively. For almost dose-volumetric parameters of PTV, the relative dose differences are statistically significant while there are no statistical significance for normal tissues. Both AXBw and AXBm was tended to underestimate dose for PTV and normal tissues compared to AAA. For analyzing two dose reporting modes in AXB, the dose distribution calculated by AXBw was similar to those of AAA when comparing the dose distributions between AAA and AXBm.
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Fig. 1.
The averaged dose-volume histograms (DVHs) (a) and the mean values of the relative dose differences (b) for PTV and normal tissue in the case of head and neck. Solid lines, dotted lines, and dashed lines are for DVHs calculated by AAA, AXBw and AXBm, respectively. The Dn% (structure) means dose received n% volume of certain structure. Vn Gy (structure) means the percent volume of certain structure irradiated by at least n Gy. The minimum dose, maximum dose, and mean dose were abbreviated to min, max, and mean, respectively. The PTV, spinal cord, brain stem, optical chiasm, left parotid grand and right parotid grand were abbreviated to P, SC, BS, OC, PL and PR, respectively.
Fig. 2.
The averaged dose-volume histograms (DVHs) (a) and the mean values of the relative dose differences (b) for PTV and normal tissue in the case of prostate. Solid lines, dotted lines, and dashed lines are for DVHs calculated by AAA, AXBw and AXBm, respectively. The Dn% (structure) means dose received n% volume of certain structure. Vn Gy (structure) means the percent volume of certain structure irradiated by at least n Gy. The minimum dose, maximum dose, and mean dose were abbreviated to min, max, and mean, respectively. The PTV, rectum, bladder, left femur head and right femur head were abbreviated to P, R, B, FL and FR, respectively.
Fig. 3.
The averaged dose-volume histograms (DVHs) (a) and the mean values of the relative dose differences (b) for PTV and normal tissue in the case of Spine. Solid lines, dotted lines, and dashed lines are for DVHs calculated by AAA, AXBw and AXBm, respectively. The Dn% (structure) means dose received n% volume of certain structure. Vn Gy (structure) means the percent volume of certain structure irradiated by at least n Gy. The minimum dose, maximum dose, and mean dose were abbreviated to min, max, and mean, respectively. The PTV, left kidney and right kidney were abbreviated to P, KL and KR, respectively.
Fig. 4.
The averaged dose-volume histograms (DVHs) (a) and the mean values of the relative dose differences (b) for PTV and normal tissue in the case of lung. Solid lines, dotted lines, and dashed lines are for DVHs calculated by AAA, AXBw and AXBm, respectively. The Dn% (structure) means dose received n% volume of certain structure. Vn Gy (structure) means the percent volume of certain structure irradiated by at least n Gy. The minimum dose, maximum dose, and mean dose were abbreviated to min, max, and mean, respectively. The PTV, spinal cord, heart, left lung, and right lung were abbreviated to P, SC, H, LL, and LR, respectively.
Table 1.
The mean dose-volumetric parameters of PTV and normal tissues for head and neck cases.
| AAA | AXBm | AXBw | pA∗ | pB † | pC ‡ | |
|---|---|---|---|---|---|---|
| PTV | ||||||
| D95% (Gy) | 70.7±0.2 | 69.6±0.4 | 70.7±0.3 | ＜0.001 | 0.992 | ＜0.001 |
| D5% (Gy) | 67.5±0.0 | 66.0±0.2 | 67.2±0.2 | ＜0.001 | ＜0.001 | ＜0.001 |
| Min (Gy) | 51.6±4.8 | 50.4±4.6 | 51.4±5.4 | 0.552 | 0.916 | 0.652 |
| Max (Gy) | 73.1±0.6 | 73.0±0.9 | 75.4±1.0 | 0.879 | ＜0.001 | ＜0.001 |
| Mean (Gy) | 69.3±0.1 | 67.9±0.2 | 69.1±0.2 | ＜0.001 | 0.075 | ＜0.001 |
| Spinal cord | ||||||
| Max (Gy) | 42.9±1.0 | 41.6±0.9 | 42.3±0.9 | 0.005 | 0.159 | 0.079 |
| Brain stem | ||||||
| Max (Gy) | 52.9±1.0 | 52.0±1.2 | 52.9±1.1 | 0.072 | 0.885 | 0.103 |
| Optic chiasm | ||||||
| Max (Gy) | 27.7±16.7 | 27.1±16.9 | 27.6±17.1 | 0.931 | 0.987 | 0.945 |
| Left parotid gland | ||||||
| V20 Gy (%) | 48.2±14.9 | 47.0±14.6 | 47.8±14.6 | 0.857 | 0.950 | 0.905 |
| Mean (Gy) | 25.0±4.3 | 24.3±4.2 | 24.7±4.2 | 0.749 | 0.898 | 0.848 |
| Right parotid gland | d | |||||
| V20 Gy (%) | 51.5±5.7 | 50.3±5.9 | 51.2±5.9 | 0.648 | 0.911 | 0.736 |
| Mean (Gy) | 26.3±2.2 | 25.6±2.2 | 26.0±2.2 | 0.530 | 0.799 | 0.711 |
Table 2.
The mean dose-volumetric parameters of PTV and normal tissues for prostate cases.
| AAA | AXBm | AXBw | pA∗ | pB† | pC ‡ | |
|---|---|---|---|---|---|---|
| PTV | ||||||
| D95% (Gy) | 73.7±0.4 | 73.4±0.3 | 73.6±0.5 | 0.077 | 0.476 | 0.383 |
| D5% (Gy) | 70.1±0.2 | 68.9±0.2 | 69.2±0.3 | ＜0.001 | ＜0.001 | 0.017 |
| Min (Gy) | 61.5±3.6 | 59.6±3.0 | 59.8±3.3 | 0.225 | 0.301 | 0.880 |
| Max (Gy) | 76.7±0.8 | 77.3±0.9 | 77.6±0.9 | 0.103 | 0.023 | 0.533 |
| Mean (Gy) | 72.2±0.3 | 71.3±0.3 | 71.9±0.4 | ＜0.001 | 0.079 | 0.003 |
| Rectum | ||||||
| D70% (Gy) | 17.6±2.9 | 16.8±2.9 | 17.0±3.0 | 0.555 | 0.657 | 0.886 |
| Mean (Gy) | 31.6±2.7 | 30.9±2.8 | 31.1±2.7 | 0.564 | 0.725 | 0.821 |
| Bladder | ||||||
| D70% (Gy) | 15.8±10.3 | 15.3±10.2 | 15.5±10.3 | 0.921 | 0.955 | 0.966 |
| Mean (Gy) | 33.1±8.8 | 32.4±8.7 | 32.8±8.8 | 0.863 | 0.953 | 0.910 |
| Left femur head | ||||||
| D50% (Gy) | 14.0±4.4 | 13.7±4.3 | 14.0±4.4 | 0.850 | 0.981 | 0.868 |
| Max (Gy) | 25.9±5.3 | 25.2±5.1 | 25.8±5.2 | 0.775 | 0.979 | 0.793 |
| Right femur head | ||||||
| D50% (Gy) | 14.5±4.7 | 14.1±4.6 | 14.5±4.7 | 0.864 | 0.992 | 0.871 |
| Max (Gy) | 25.2±5.5 | 24.6±5.3 | 25.2±5.4 | 0.799 | 0.985 | 0.782 |
Table 3.
The mean dose-volumetric parameters of PTV and normal tissues for spine cases.
| AAA | AXBm | AXBw | pA∗ | pB † | pC ‡ | |
|---|---|---|---|---|---|---|
| PTV | ||||||
| D95% (Gy) | 8.3±0.1 | 8.2±0.1 | 8.4±0.1 | 0.001 | 0.055 | ＜0.001 |
| D5% (Gy) | 8.0±0.0 | 7.8±0.0 | 8.0±0.0 | ＜0.001 | 0.015 | ＜0.001 |
| Min (Gy) | 6.8±1.1 | 6.6±1.0 | 6.7±1.0 | 0.619 | 0.771 | 0.831 |
| Max (Gy) | 8.7±0.1 | 8.6±0.1 | 9.2±0.1 | 0.657 | ＜0.001 | ＜0.001 |
| Mean (Gy) | 8.2±0.0 | 8.0±0.0 | 8.2±0.0 | ＜0.001 | 0.673 | ＜0.001 |
| Left kidney | ||||||
| D50% (Gy) | 0.8±0.9 | 0.8±0.9 | 0.8±0.9 | 0.958 | 0.980 | 0.979 |
| Max (Gy) | 3.7±3.2 | 3.6±3.1 | 3.6±3.1 | 0.936 | 0.953 | 0.983 |
| Right kidney | ||||||
| D50% (Gy) | 0.7±0.8 | 0.7±0.8 | 0.7±0.8 | 0.950 | 0.971 | 0.979 |
| Max (Gy) | 3.6±3.3 | 3.5±3.3 | 3.6±3.3 | 0.947 | 0.965 | 0.982 |
Table 4.
The mean dose-volumetric parameters of PTV and normal tissues for lung cases.
| AAA | AXBm | AXBw | pA∗ | pB † | pC ‡ | |
|---|---|---|---|---|---|---|
| PTV | ||||||
| D95% (Gy) | 63.1±0.7 | 63.5±1.0 | 63.4±1.0 | 0.319 | 0.424 | 0.851 |
| D5% (Gy) | 60.5±0.7 | 59.9±1.0 | 60.1±1.0 | 0.136 | 0.303 | 0.671 |
| Min (Gy) | 56.8±0.7 | 55.9±1.1 | 56.3±1.0 | 0.032 | 0.189 | 0.373 |
| Max (Gy) | 64.5±0.9 | 65.7±1.1 | 65.3±1.4 | 0.017 | 0.166 | 0.480 |
| Mean (Gy) | 62.0±0.7 | 61.9±1.0 | 62.0±0.9 | 0.792 | 0.862 | 0.930 |
| Spinal cord | ||||||
| V13.5 Gy (%) | 1.9±2.6 | 1.4±2.2 | 1.6±2.4 | 0.645 | 0.748 | 0.892 |
| Max (Gy) | 13.5±5.1 | 13.0±4.8 | 13.2±4.8 | 0.812 | 0.883 | 0.926 |
| Heart | ||||||
| V27.5 Gy (%) | 0.0±0.0 | 0.0±0.0 | 0.0±0.0 | 0.702 | 0.900 | 0.785 |
| Max (Gy) | 13.0±9.9 | 12.9±9.8 | 12.9±9.8 | 0.984 | 0.982 | 0.999 |
| Left lung | ||||||
| V20 Gy (%) | 3.0±4.9 | 3.0±4.9 | 3.0±4.9 | 0.998 | 0.996 | 0.999 |
| Mean (Gy) | 2.5±2.5 | 2.5±2.5 | 2.5±2.5 | 0.989 | 0.992 | 0.997 |
| Right lung | ||||||
| V20 Gy (%) | 4.6±4.8 | 4.6±4.9 | 4.6±4.9 | 0.983 | 0.980 | 0.997 |
| Mean (Gy) | 3.1±2.4 | 3.1±2.4 | 3.1±2.4 | 0.996 | 0.999 | 0.996 |
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