Department of Nuclear Engineering, Hanyang University, Seoul, Republic of Korea.
Med Phys. 2012 Feb;39(2):1001-5. doi: 10.1118/1.3662890.
This paper describes a new gamma-ray imaging method, "gamma electron vertex imaging (GEVI)," which can be used for precise beam range verification in proton therapy.
In GEVI imaging, the high-energy gammas from a source or nuclear interactions are first converted, by Compton scattering, to electrons, which subsequently are traced by hodoscopes to determine the location of the gamma source or the vertices of the nuclear interactions. The performance of GEVI imaging for use in-beam range verification was evaluated by Monte Carlo simulations employing geant4 equipped with the QGSP_BIC_HP physics package.
Our simulation results show that GEVI imaging can determine the proton beam range very accurately, within 2-3 mm of error, even without any sophisticated analysis. The results were obtained under simplified conditions of monoenergetic pencil beams stopped in a homogeneous phantom and on the basis of the obtained results it is expected to achieve submillimeter accuracy in proton beam range measurement.
If future experimental work confirms the simulated results presented in this paper, the use of GEVI imaging is expected to have a great potential in increasing the accuracy of proton beam range verification in a patient, resulting in significant improvement of treatment effectiveness by enabling tight conformation of radiation dose to the tumor volume and patient safety.
本文描述了一种新的伽马射线成像方法，“伽马电子顶点成像（GEVI）”，可用于质子治疗中的精确束射程验证。
在 GEVI 成像中，源或核相互作用产生的高能伽马射线首先通过康普顿散射转换为电子，随后通过闪烁计数器追踪电子来确定伽马源的位置或核相互作用的顶点。通过使用配备 QGSP_BIC_HP 物理包的 geant4 的蒙特卡罗模拟，评估了 GEVI 成像在束内射程验证中的性能。
我们的模拟结果表明，GEVI 成像即使没有任何复杂的分析，也可以非常准确地确定质子束的射程，误差在 2-3 毫米以内。这些结果是在单能铅笔束停止在均匀体模中和基于获得的结果的简化条件下获得的，预计在质子束射程测量中实现亚毫米精度。
如果未来的实验工作证实了本文中提出的模拟结果，那么预计 GEVI 成像的使用将具有很大的潜力，可以提高患者中质子束射程验证的准确性，从而通过将辐射剂量紧密符合肿瘤体积并提高患者安全性来显著提高治疗效果。
