摘要
目的探讨不同呼吸波段引起的肺组织体积与密度变化对放射治疗中小野剂量计算的影响,为临床治疗计划系统与呼吸管理技术的应用提供参考。方法首先基于蒙特卡罗方法计算在标准模体下的百分深度剂量(PDD)与离轴比(Profile)结果,用于分析侧向电子不平衡现象对于组织剂量计算的影响。在4D-CT图像下通过指定肺密度的方法建立人体动态肺部呼吸模型,评价正常肺组织由于体积与密度变化引起的实际接收剂量的差异。结果在标准模体下不同状态肺组织PDD差异最大为44.25%,软组织PDD差异最大为13.82%,肺组织密度越低侧向电子不平衡现象越严重,剂量计算误差越大。在人体模型下正常肺组织高剂量区不同状态体积差异最大为-5%,低剂量区不同状态体积差异最大为8%,同时靶区剂量差异最大为15%,且靶区越大差异越大。结论在呼吸门控技术下临床医生可结合TPS算法在吸气末进行靶区勾画,对于肺功能较好的患者可采用深吸气屏气技术,以降低放射治疗中正常肺组织接收剂量、提高靶区接收剂量。
Objective To investigate the effect of lung tissue volume and density changes caused by different respiratory wavelengths on the calculation of small field doses in radiation therapy,and to provide a reference for the application of clinical treatment planning system(TPS)and respiratory management techniques.Methods The percent depth dose(PDD)and profile in a standard phantom were calculated based on the Monte Carlo method to analyze the effect of lateral electronic disequilibrium on tissue dose calculation.A human dynamic lung respiration model was established by specifying the lung density on 4D-CT to eva-luate the differences in actual dose received by the normal lung tissue due to volume and density changes.Results In the standard phantom,the maximum difference in PDD of lung tissue under different states was 44.25%,and the maximum difference in PDD of soft tissue was 13.82%;as the density of lung tissue decreased,the lateral electronic disequilibrium and the error of dose calculation increased.In the human model,the maximum difference in volume of normal lung tissue under different states was-5%in the high-dose area and 8%in the low-dose area;the maximum difference in dose in the target area was 15%,and the larger the target area,the greater the difference.Conclusion With the respiratory gating technique,clinicians can use the TPS algorithm to outline the target area at the end of inspiration,and for patients with good lung function,the deep inspiration breath-hold technique can be used to reduce the dose to normal lung tissue and increase the dose to the target area.
作者
肖杨
黄顺平
李恒
吴艳
李进
XIAO Yang;HUANG Shunping;LI Heng;WU Yan;LI Jin(Tumor Center, The Second Affiliated Hospital of Chongqing Medical University, Chongqing 410000, China)
出处
《精准医学杂志》
2021年第5期422-427,共6页
Journal of Precision Medicine
基金
重庆市科卫联合医学科研项目(2021MSXM086)。
关键词
模型
结构
肺
呼吸
四维计算机体层摄影术
蒙特卡罗法
算法
放射治疗计划
计算机辅助
放射治疗剂量
Models,structural
Lung
Respiration
Four-dimensional computed tomography
Monte carlo method
Algorithms
Radiotherapy planning,computer-assisted
Radiotherapy dosage
