Soh Roger Cai Xiang, Tay Guan Heng, Lew Wen Siang, Lee James Cheow Lei
Department of Radiation Oncology, National University Cancer Institute, Singapore.
Division of Physics and Applied Physics, Nanyang Technological University, Singapore.
Rep Pract Oncol Radiother. 2018 Sep-Oct;23(5):413-424. doi: 10.1016/j.rpor.2018.08.003. Epub 2018 Sep 3.
To identifying depth dose differences between the two versions of the algorithms using AIP CT of a 4D dataset.
Motion due to respiration may challenge dose prediction of dose calculation algorithms during treatment planning.
The two versions of depth dose calculation algorithms, namely, Anisotropic Analytical Algorithm (AAA) version 10.0 (AAAv10.0), AAA version 13.6 (AAAv13.6) and Acuros XB dose calculation (AXB) algorithm version 10.0 (AXBv10.0), AXB version 13.6 (AXBv13.6), were compared against a full MC simulated 6X photon beam using QUASAR respiratory motion phantom with a moving chest wall. To simulate the moving chest wall, a 4 cm thick wax mould was attached to the lung insert of the phantom. Depth doses along the central axis were compared in the anterior and lateral beam direction for field sizes 2 × 2 cm, 4 × 4 cm and 10 × 10 cm.
For the lateral beam direction, the moving chest wall highlighted differences of up to 105% for AAAv10.0 and 40% for AXBv10.0 from MC calculations in the surface and buildup doses. AAAv13.6 and AXBv13.6 agrees with MC predictions to within 10% at similar depth. For anterior beam doses, dose differences predicted for both versions of AAA and AXB algorithm were within 7% and results were consistent with static heterogeneous studies.
The presence of the moving chest wall was capable of identifying depth dose differences between the two versions of the algorithms. These differences could not be identified in the static chest wall as shown in the anterior beam depth dose calculations.
使用4D数据集的AIP CT识别两种算法版本之间的深度剂量差异。
呼吸引起的运动可能会在治疗计划期间对剂量计算算法的剂量预测构成挑战。
将两种深度剂量计算算法版本，即各向异性分析算法（AAA）版本10.0（AAAv10.0）、AAA版本13.6（AAAv13.6）以及Acuros XB剂量计算（AXB）算法版本10.0（AXBv10.0）、AXB版本13.6（AXBv13.6），与使用带有移动胸壁的QUASAR呼吸运动体模的全蒙特卡罗模拟6X光子束进行比较。为模拟移动胸壁，在体模的肺部插入物上附着一个4厘米厚的蜡模。在2×2厘米、4×4厘米和10×10厘米的射野尺寸下，比较前束和侧束方向沿中心轴的深度剂量。
对于侧束方向，移动胸壁突出显示，AAAv10.0在表面剂量和建成剂量方面与蒙特卡罗计算的差异高达105%，AXBv10.0高达40%。AAAv13.6和AXBv13.6在相似深度下与蒙特卡罗预测的一致性在10%以内。对于前束剂量，AAA和AXB算法两个版本预测的剂量差异在7%以内，结果与静态非均匀性研究一致。
移动胸壁能够识别两种算法版本之间的深度剂量差异。如在前束深度剂量计算中所示，在静态胸壁中无法识别这些差异。
