磁场对MERT中次级光子剂量分布影响的蒙特卡罗研究

The study on dose distribution for secondary photon of MERT with the uniform transverse magnetic field by Monte Carlo

目的:磁场调制下的电子调强放射治疗可以有效的增加电子束的剂量跌落。电子束产生的次级光子将对靶区后的正常器官产生受量,本文以Monte Carlo的模拟计算研究磁场对电子束产生次级光子的剂量和剂量分布的影响。方法:将几种不同能量的电子束作为外照射源,以置于不同强度磁场下的三维水模为介质模型,使用FLUKA程序模拟电子束垂直入射到水模中引起的电子与物质的相互作用。结果:磁场对电子束的作用会减少水模次级光子的剂量,特别是穿透深度后的X射线污染区剂量迅速跌落。结论:磁场调制下的电子调强减少了电子束的X射线污染,这进一步降低了靶区后正常器官的受量,这意味着磁场调制下的电子调强放射治疗具有相当大的应用前景,但同时为磁场与放疗设备的整合和剂量算法研究带来了挑战。

objective： The modulated electron radiation therapy（MERT） with the uniform transverse magnetic field formed a sharp depth-dose drop-off. The secondary photon produced by electron beam exposed the normal tissues after the target. Monte Carlo simulations were employed to study the characteristics of the dose distribution of secondary photon in the presence of uniform transverse magnetic field. Methods： Set the electron with different energy as the external beam source, 3-dimensional water phantom as the media and the FLUKA program was used to perform the reactions between electron and material in the water phantom. Results： The dose of secondary photon was reduced because of the influence of magnetic field for the electron beam, especially the dose of x-ray pollution area was a sharp drop-off. Conclusion： The modulated electron radiation therapy（MERT） with the uniform transverse magnetic field reduces the pollution of electron beam of x-rays. It means that using magnetic fields in conjunction with electron radiation therapy has great application prospect, but it also has brought new challenges for the research of the integration of radiotherapy equipment with magnetic field and dose algorithm.