Physical characterization of single convergent beam device for teletherapy: theoretical and Monte Carlo approach
Physical characterization of single convergent beam device for teletherapy: theoretical and Monte Carlo approach
复制标题
用于远程治疗的单会聚光束装置的物理表征：理论和蒙特卡罗方法
DOI：
10.1088/0031-9155/60/18/7191
复制
发表时间：
2015
影响因子：
3.5
通讯作者：
Mauro Valente
中科院分区：
文献类型：
--
作者：
R. Figueroa;Mauro Valente
这项工作的主要目的是确定一种新的放射治疗远程治疗装置的可行性和物理特性，该装置基于像放射治疗中使用的能量的会聚x射线束的应用，向目标提供高度集中的剂量。我们将其命名为会聚束放射疗法（CBRT）。为了确定理想的会聚光子束在假想水影中的剂量学特性，首先发展了分析方法。然后，利用PENELOPE蒙特卡罗代码，将类似的会聚光束应用于水影与解析方法进行了比较。CBRT器件（Converay®）设计用于适应LINACs的头部。会聚束光子效应是由于LINAC电子在产生轫致辐射（高能x射线）的大型薄球形帽目标上的垂直撞击而实现的。这样，电子冲击在帽的各个点上（CBRT条件），瞄准焦点。随着X射线（轫致辐射）向前引导，一个可移动准直器系统从输出端发射出许多光束，形成一个几乎确定的会聚光束。其他蒙特卡罗模拟是在现实条件下进行的。以r半径约为10 ~ 30 cm，曲率半径约为70 ~ 100 cm的大而薄的球形帽为目标，以及以帽的焦点为中心的立方体水影为目标进行了模拟。考虑了不同能量和帽厚下轫致辐射与水影的所有相互作用机制。此外，电场和/或磁场的大小，这是必要的转移临床使用的电子束（0.1至20兆电子伏特），是确定电磁方程与相对论修正。通过这种方式，可以操纵和引导上述光束垂直撞击球形帽。获得的第一个结果显示深度剂量峰，其形状与强子治疗技术的形状相似。所得结果表明，在焦点或等中心处产生深度剂量峰。这些结果与用蒙特卡罗代码得到的结果一致。峰值聚焦与光子束的能量无关，但其强度与之无关。用蒙特卡罗程序模拟的结果表明，薄壁帽上产生的轫致辐射主要指向焦点。每个冲击点的孔径角主要取决于能量束、原子序数Z和目标的厚度。还有一个多准直器同轴于有许多孔的帽或环，允许一个干净的汇聚出口x射线束，其剂量分布与理想情况相似。控制CBRT几何结构中电子束偏转所需的电场和磁场是高度可行的，使用专门设计的电气和/或磁性设备，分别具有技术上可实现的电压和电流值。然而，人们发现磁性器件是电子束控制的更合适的选择，特别是在高能量下。主要结论是，这种装置的发展是可行的。由于其特点，该技术可能被认为是光子外部放射治疗的有力新工具。
The main purpose of this work is to determine the feasibility and physical characteristics of a new teletherapy device of radiation therapy based on the application of a convergent x-ray beam of energies like those used in radiotherapy providing highly concentrated dose delivery to the target. We have denominated it Convergent Beam Radio Therapy (CBRT). Analytical methods are developed first in order to determine the dosimetry characteristic of an ideal convergent photon beam in a hypothetical water phantom. Then, using the PENELOPE Monte Carlo code, a similar convergent beam that is applied to the water phantom is compared with that of the analytical method. The CBRT device (Converay®) is designed to adapt to the head of LINACs. The converging beam photon effect is achieved thanks to the perpendicular impact of LINAC electrons on a large thin spherical cap target where Bremsstrahlung is generated (high-energy x-rays). This way, the electrons impact upon various points of the cap (CBRT condition), aimed at the focal point. With the X radiation (Bremsstrahlung) directed forward, a system of movable collimators emits many beams from the output that make a virtually definitive convergent beam. Other Monte Carlo simulations are performed using realistic conditions. The simulations are performed for a thin target in the shape of a large, thin, spherical cap, with an r radius of around 10–30 cm and a curvature radius of approximately 70 to 100 cm, and a cubed water phantom centered in the focal point of the cap. All the interaction mechanisms of the Bremsstrahlung radiation with the phantom are taken into consideration for different energies and cap thicknesses. Also, the magnitudes of the electric and/or magnetic fields, which are necessary to divert clinical-use electron beams (0.1 to 20 MeV), are determined using electromagnetism equations with relativistic corrections. This way the above-mentioned beam is manipulated and guided for its perpendicular impact upon the spherical cap. The first results that were achieved show in-depth dose peaks, having shapes qualitatively similar to those from hadrontherapy techniques. The obtained results demonstrate that in-depth dose peaks are generated at the focus point or isocenter. These results are consistent with those obtained with Monte Carlo codes. The peak-focus is independent of the energy of the photon beam, though its intensity is not. The realistic results achieved with the Monte Carlo code show that the Bremsstrahlung generated on the thin cap is mainly directed towards the focus point. The aperture angle at each impact point depends primarily on the energy beam, the atomic number Z and the thickness of the target. There is also a poly-collimator coaxial to the cap or ring with many holes, permitting a clean convergent-exit x-ray beam with a dose distribution that is similar to the ideal case. The electric and magnetic fields needed to control the deflection of the electron beams in the CBRT geometry are highly feasible using specially designed electric and/or magnetic devices that, respectively, have voltage and current values that are technically achievable. However, it was found that magnetic devices represent a more suitable option for electron beam control, especially at high energies. The main conclusion is that the development of such a device is feasible. Due to its features, this technology might be considered a powerful new tool for external radiotherapy with photons.
影响因子：
3.8
作者：
MACKIE, TR;HOLMES, T;KINSELLA, T
通讯作者：
KINSELLA, T
影响因子：
3.8
作者：
SPIROU, SV;CHUI, CS
通讯作者：
CHUI, CS