颅内肿瘤放疗中kV级锥形束CT引导引入的眼晶体吸收剂量研究

Discussion on absorbed dose of eye lens guided by kV cone beam CT in intracranial tumor radiotherapy

目的:研究颅内肿瘤放疗中kV级锥形束CT(cone-beam CT,CBCT)引导引入的眼晶体吸收剂量,为颅内肿瘤放疗中计算眼晶体的额外吸收剂量提供数据支持。方法:选取某院2014年6月至2016年5月的30例颅内肿瘤放疗病例,将30例病例的计划CT数据导入EGSnrc程序进行Monte Carlo模拟,分析高质量头、标准剂量头、低剂量头和头部4种扫描协议5个等中心位置下的CBCT引导引入的眼晶体吸收剂量。采用SPSS 26.0进行统计学分析。结果:同一扫描协议不同等中心的眼晶体吸收剂量结果显示,除位于眼晶体后方的等中心的吸收剂量与其他4个等中心差异有统计学意义外(P<0.001),其余4个等中心间差异均无统计学意义(P>0.05);每个等中心不同扫描协议下的眼晶体吸收剂量差异均有统计学意义(P<0.001)。结论:不同的扫描协议、不同的等中心位置对CBCT引导引入的眼晶体吸收剂量均有影响,前者大于后者;CBCT引导引入的眼晶体吸收剂量不容忽视,引导次数较多时应在治疗计划中充分考虑其影响。

Objective To obtain the absorbed dose of the eye lens guided by kV cone beam CT(CBCT)in radiotherapy of intracranial tumor,and to provide data support for considering the extra absorbed dose of the eye lens in radiotherapy of intracranial tumor.Methods Totally 30 intracranial tumor patients undergoing radiotherapy from June 2014 to May 2016 at a hospital were selected,and their planning CT data were imported into EGSnrc program for Monte Carlo simulation to analyze the CBCT-guided absorbed dose of the eye lens at 5 isocenters for 4 scanning protocols of high quality head,standard dose head,low dose head and head.Statistical analysis was performed using SPSS 26.0.Results The results of the absorbed dose of the eye lens with different isocenters in the same scanning protocol showed that the differences were statistically significant between the doses for the isocenter located behind the eye lens and those in the other four isocenters(P<0.001),while the absorbed doses for the four isocenters were not statistically different(P>0.05);the differences in absorbed doses of the eye lens for each isocenter in different scanning protocols were statistically significant(P<0.001).Conclusion The comparative analysis indicates that the scanning protocol has greater effects on the absorbed dose of the eye lens guided by CBCT than the isocenter position.The CBCT-guided absorbed dose of the eye lens should not be neglected,and its impact should be fully considered in the treatment planning in case of multiple times of CBCT guidance.