CT值用于质子治疗计划系统中质子入射能量的计算

目的 探索CT值用于质子治疗计划系统计算质子入射能量的方法。方法 通过分析Bethe-Block公式和质子射程计算公式,研究质子治疗能量范围(70~250 MeV)质子束在各种辐射等效材料中与水中的射程的比例关系。利用蒙特卡罗方法SRIM2008程序验证此比例系数存在恒值的可能性。通过Origin 8.0软件对此射程比例系数(C_i)和相应辐射等效材料的CT值进行指数函数拟合,研究CT值与射程比例系数的函数关系。分析CT测量原理和利用射程比系数将质子治疗的实际射程等效为水中的射程,从而反推入射质子所需的能量。结果 质子治疗能量范围(70~250 MeV)质子束在辐射等效材料中的射程与此能量质子束在水中的射程的比值存在恒定的比例系数(C_i)。CT值与射程比例系数相关(r=0.999)。可以将特定能量质子在辐射等效材料中的射程等效为水中的射程。结论 本研究利用机体各体积单元CT值与射程比例系数(C_i),精确计算实际照射肿瘤部位所需射程的水中等效射程,由水中等效射程计算出Bragg峰位落在肿瘤部位所需的入射质子束能量。本研究为CT技术用于质子治疗计划系统提出了一种新的探索。

Application of CT values in calculation of proton incident energy in proton treatment planning system

Objective To explore the application of CT value in calculating the proton incident energy in proton treatment planning system. Methods Bethe-Block formula and the formula for calculating the proton range were analyzed to study the correlation of the range of proton beam (70-250 MeV) between a variety of radiation equivalent material and water. Procedure of Monte Carlo SRIM2008 was used to verify the possibility of a constant proportional coefficient of range(C_i). The proportional coefficient (C_i) of range in radiation-equivalent material and the CT value were fitted by using Origin 8.0 software to study the functional relation of CT value and C_i. The actual range of proton was equivalent to a range of water and incident proton energy could be calculated. Results There was a constant range of C_i of proton beam (70-250 MeV) between a variety of radiation equivalent material and water. There was a functional relation between CT value and C_i (r = 0.999). The actual range of proton in radiation equivalent material can be equivalent to a range of the water.Conclusions CT values and a range of proportional coefficient (C_i), and the actual required range of the tumor could be used to accurately calculate the water equivalent range, and the incident proton energy to the position of Bragg peak. A new exploration for using CT technology in proton treatment planning system could be obtained.