Rezaee Ladan
Department of Physics, Shiraz Branch, Islamic Azad University, Shiraz, Iran.
Rep Pract Oncol Radiother. 2018 Sep-Oct;23(5):433-441. doi: 10.1016/j.rpor.2018.08.004. Epub 2018 Sep 4.
Design of a numerical method for creating spread-out Bragg peak (SOBP) and evaluation of the best parameter in Bortfeld Model to this aim in oxygen ion therapy.
In radiotherapy, oxygen ions have more biological benefits than light beams. Oxygen ions have a higher linear energy transfer (LET) and larger relative biological effectiveness (RBE) than lighter ones.
For the design of the spread-out Bragg peak (SOBP) for oxygen beam, we designed a numerical method using the Geant4 Monte Carlo simulation code, along with matrix computations.
The profiles of the Bragg Peak have been calculated for each section in the target area by the Geant4 tool. Then, in order to produce SOBP smoothly, a set of weighting factors for the intensity of oxygen ion radiation in each energy was extracted through a numerically designed method. This method was tested for producing SOBP at various widths and at different depths of a phantom. Also, weighting factors of intensity for producing a flat SOBP with oxygen ions were also obtained using the Bortfeld model in order to determine the best parameters. Then, the results of the Bortfeld model were compared with the outcomes of the method that was developed in this study.
The results showed that while the SOBP designed by the Bortfeld model has a homogeneity of 92-97%, the SOBP designed by the numerical method in the present study is above 99%, which in some cases even closed to 100%.
设计一种用于产生扩展布拉格峰（SOBP）的数值方法，并评估博尔特费尔德模型中实现此目的的最佳参数用于氧离子治疗。
在放射治疗中，氧离子比光束具有更多的生物学益处。氧离子比轻离子具有更高的线能量转移（LET）和更大的相对生物学效应（RBE）。
为设计氧离子束的扩展布拉格峰（SOBP），我们使用Geant4蒙特卡罗模拟代码并结合矩阵计算设计了一种数值方法。
通过Geant4工具计算了靶区各部分的布拉格峰轮廓。然后，为了平滑地产生SOBP，通过数值设计的方法提取了每个能量下氧离子辐射强度的一组加权因子。该方法在不同宽度和不同深度的体模中产生SOBP时进行了测试。此外，还使用博尔特费尔德模型获得了用氧离子产生平坦SOBP的强度加权因子，以确定最佳参数。然后，将博尔特费尔德模型的结果与本研究开发的方法的结果进行了比较。
结果表明，虽然博尔特费尔德模型设计的SOBP均匀性为92 - 97%，但本研究中数值方法设计的SOBP高于99%，在某些情况下甚至接近100%。
