Influence of heterogeneous media on Very High Energy Electron (VHEE) dose penetration and a Monte Carlo-based comparison with existing radiotherapy modalities
Influence of heterogeneous media on Very High Energy Electron (VHEE) dose penetration and a Monte Carlo-based comparison with existing radiotherapy modalities
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DOI：
10.1016/j.nimb.2020.09.008
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发表时间：
2020-11-01
影响因子：
1.3
通讯作者：
Jones, Roger M.
中科院分区：
文献类型：
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作者：
Lagzda, Agnese;Angal-Kalinin, Deepa;Jones, Roger M.
本文研究了靶材不均匀性对VHEE(VHEE)束流剂量分布的剂量学影响。测量了156 MeV VHEE束流对水中高密度和低密度(0.001~2.2g/cm(3))埋入介质的剂量分布敏感性。据作者所知，这是第一次在这种高能电子束下对非均匀靶进行剂量穿透的系统实验。剂量学实验的结果与TOPAS/GEANT4蒙特卡罗程序的模拟结果进行了比较，并与光子和质子束的灵敏度进行了比较。然后用窄(sigma=1.2 mm)高斯VHEE光束照射该装置。使用辐射敏感的EBT-XD气致变色胶片记录了水模内不同深度的横向剂量分布。使用GEANT4蒙特卡罗工具包的TOPAS User WRAP对来自CLEAR设备的测量束和靶几何参数进行了模拟，并与光子和质子束对水模体中不均匀的敏感性进行了比较。在所有记录的深度(0-20厘米)上，所有测量的剂量数据的剂量偏差小于8%。在整个水模体积内的蒙特卡罗模拟显示了15%的剂量偏差。模拟研究表明，在该实验装置的MC模拟中，在治疗能量范围内使用质子和光子束，中心平面的剂量变化分别高达中心平面最大剂量的100%和74%。这些实验的剂量学结果与TOPAS/GEANT4模拟的剂量学结果相吻合。与治疗性质子束的模拟结果(高达平面内最大剂量的100%)相比，VHEE束的剂量分布对嵌入的高密度和低密度几何形状相对不敏感(中心平面上的剂量差为15%)。因此，VHEE对解剖学变化有很强的抵抗力，有可能成为治疗肺部等高度不均匀和活动区域肿瘤的一种可靠的放射治疗模式。
In this paper we investigate the dosimetric effects target inhomogeneities on VHEE (Very High Energy Electron) beam dose profiles. Dose profile sensitivity to high and low density (0.001 -2.2 g/cm(3)) embedded media in water was measured for 156 MeV VHEE beams. To the knowledge of the authors, this is the first systematic experiment on dose penetration in inhomogeneous targets at this high energy electron beams. The results of the dosimetry experiments were compared with simulation results acquired with the TOPAS/GEANT4 Monte Carlo codes and were compared with the sensitivity of photon and proton beams.Dosimetry experiments with VHEE beams at 156 MeV were performed by embedding various density inserts in a cuboid 30 x 30 x 10 cm(3) water phantom. This setup was then irradiated with a narrow (sigma = 1.2 mm) Gaussian VHEE beams. Transverse dose profiles were recorded at various depths within the water phantom using radosensitive EBT-XD Gafchromic films. Simulations were performed using the TOPAS user wrap for the GEANT4 Monte Carlo toolkit with the measured beam and target geometry parameters from the CLEAR facility and compared with sensitivity of photon and protons beams to inhomogeneities in water phantoms.Less than 8% dose deviation was shown for all measured dose data across all recorded depths (0-20 cm). Monte Carlo simulations within the whole water phantom volume showed a 15% dose deviation. Simulation studies indicated that using proton and photon beams within a therapeutic energy range in MC simulations of this experimental setup resulted in dose change in the central plane up to 100% and 74% of the dose maximum in the central plane respectively.The dosimetry results of these experiments and TOPAS/GEANT4 simulations compare well. Dose profiles of VHEE beams were found to be relatively insensitive (< 15% dose difference across the central plane) to embedded high and low density geometries compared to simulation results with therapeutic proton beams (up to 100% of dose maximum in the plane). Therefore, VHEE is robust to anatomical changes and has the potential to be a reliable mode of radiotherapy for treating tumors in highly inhomogeneous and mobile regions such as the lung.