Step-size effect on calculated photon and electron beam Cherenkov-to-dose conversion factors.
Step-size effect on calculated photon and electron beam Cherenkov-to-dose conversion factors.
复制标题
DOI：
10.1016/j.ejmp.2020.08.015
复制
发表时间：
2020-10
期刊：
影响因子：
--
通讯作者：
Seuntjens J
中科院分区：
文献类型：
--
作者：
Zlateva Y;Muir BR;El Naqa I;Seuntjens J
先前的工作提出并验证了基于切伦科夫发射（CE）的水中放射治疗剂量学。然而，具有<4π CE检测的浓缩历史蒙特卡罗（MC）计算的电子束CE到剂量转换可能表现出步长依赖性。这项工作提出了一个物理更新和数值研究，这种步长依赖于光子和电子束，阐明CE代物理，并指导进一步的研究。计算了水中轴上光子（6X，15 X）和电子（6 E，20 E）的CE-剂量转换：θ ± δθ ∈ {90° ± 90°（4π），90° ± 5°，45° ± 45°，90° ± 45°}，10 cm等效正方形，100 cm SSD，1 cm体素半径和射束依赖长度。与单次散射（SS）模拟的相对偏差根据最大分数电子台阶能量损失ESTEPE ∈ [0.01 - 0.25]进行评估。标准不确定度（k = 1，108历史）的报告。还实现了仅考虑直线步进方向的简化方法。除了不推荐的90° ± 5°（− 1.6% ± 0.5%，20 E）表面剂量测定外，未观察到剂量和所有剂量的显著步长效应（>0.1%）。电子SS偏差不确定性（k = 1），否则，从<0.2%的整体变化到<0.1%的大孔径。光子不确定性从总体<1.1%变化到大孔径的非表面<0.2%。简化的直步法显示出与SS的总体偏差更大，对于ESTEPE ∈ [0.10，0.25]，最显著的是表面上为90° ± 45°的− 2.8% ± 0.1%（6 E）和− 2.5% ± 0.4%（20 E），非表面上为90° ± 5°的− 1.4% ± 0.3%（6X）和− 0.6% ± 0.2%（15 X）。我们证明了EGSnrc方向切伦科夫计算中新实施的校正的步长独立性。这推进了临床CE为基础的剂量测定，是有用的一般蒙特卡罗社区。
Previous work presented and validated in-water Cherenkov emission (CE)-based radiotherapy dosimetry. Condensed history Monte Carlo (MC)-calculated electron beam CE-to-dose conversion with <4π CE detection, however, could exhibit step-size dependence. This work presents a physics update and numerical study of this step-size dependence in photon and electron beams, elucidates the CE generation physics, and guides further research. The CE-to-dose conversion, , is calculated for photons (6X, 15X) and electrons (6E, 20E) on-axis in-water with: θ ± δθ ∈ {90° ± 90° (4π), 90° ± 5°, 45° ± 45°, 90° ± 45°}, 10 cm equivalent square, 100 cm SSD, 1cm voxel radius and beam-dependent length. Relative deviation from single-scattering (SS) simulation is evaluated on maximum fractional electron step energy loss ESTEPE ∈ [0.01 – 0.25]. Standard uncertainties (k = 1, 108 histories) are reported. A simplified method considering only the straight step direction is also implemented. No significant step-size effect (>0.1%) was observed for dose and all , except for surface dosimetry at 90° ± 5° (− 1.6% ± 0.5%, 20E), which is not recommended. Electron SS deviation uncertainties (k = 1), otherwise, varied from <0.2% overall to <0.1% with large apertures. Photon uncertainties varied from <1.1% overall to <0.2% non-superficially with large apertures. The simplified straight-step method exhibited overall greater deviation from SS, most notably − 2.8% ± 0.1% (6E) and − 2.5% ± 0.4% (20E) superficially with 90° ± 45°, and − 1.4% ± 0.3% (6X) and − 0.6% ± 0.2% (15X) non-superficially with 90° ± 5° for ESTEPE ∈ [0.10, 0.25]. We demonstrate step-size independence of newly-implemented correction in EGSnrc directional Cherenkov calculations. This advances clinical CE-based dosimetry and is useful for the general Monte Carlo community.
登录
查看更多内容
影响因子：
3.8
作者：
Almond, PR;Biggs, PJ;Rogers, DWO
通讯作者：
Rogers, DWO
影响因子：
3.4
作者：
SPENCER, LV;ATTIX, FH
通讯作者：
ATTIX, FH
影响因子：
3.8
作者：
Zlateva, Yana;Muir, Bryan R.;El Naqa, Issam
通讯作者：
El Naqa, Issam
影响因子：
3.3
作者：
Nikjoo, H.;Uehara, S.;Brahme, A.
通讯作者：
Brahme, A.
影响因子：
3.8
作者：
McEwen, Malcolm;DeWerd, Larry;Seuntjens, Jan
通讯作者：
Seuntjens, Jan