宫颈癌VMAT剂量验证的γ与DVH评估及两者与剂量偏差相关性研究  

The application and correlation study of γ rule and DVH evaluation for VMAT dose verification evaluation of cervical cancer patients

作　　者：马阳光[1] 麦日珍 裴运通 王芳娜[1] 刘乐乐[1] 郭跃信[1] Ma YangGuang;Mai Rizhen;Pei Yuntong;Wang Fangna;Liu Lele;Guo Yuexin(Department of Radiation Oncology,The First Affiliated Hospital of Zhengzhou University,Zhengzhou 450052,China;Department of Medical Equipment,The First Affiliated Hospital of Zhengzhou University,Zhengzhou 450052,China)

机构地区：[1]郑州大学第一附属医院放射治疗部,郑州450052 [2]郑州大学第一附属医院医学装备部,郑州450000

出　　处：《中华放射肿瘤学杂志》2022年第5期450-455,共6页Chinese Journal of Radiation Oncology

基　　金：河南省医学科技攻关省部共建重点项目(SBGJ202102102);河南省重点研发与推广专项(212102310251);河南省高端外国专家引进计划(HNGD2022030)。

摘　　要：目的比较γ与剂量体积直方图(DVH)在宫颈癌容积调强弧形治疗(VMAT)剂量验证中的应用,并评估两者反映剂量偏差的能力。方法选取20例宫颈癌VMAT病例,由TrueBeam投照、使用FC65-G及ArcCheck测量并与Eclipse计算点、面剂量比对。由3DVH软件重建患者剂量,比较重建靶区D_(mean)、D_(95)%、D_(98)%、D_(2)%,左右股骨头V_(20Gy),直肠V_(40Gy),脊髓D1cm^(3)及50%处方剂量包绕区(IDV)D_(98)%、D_(2)%、D_(50)%与计划值差异并对各器官行三维γ分析。使用皮尔森相关系数分析点剂量偏差、二维γ通过率及其平均值、各器官三维γ通过率与剂量偏差相关性。结果电离室实测、3DVH重建与计划计算点剂量间偏差小,二维γ比对均通过(3%/3 mm,≥90%)。靶区平均剂量、IDV各参数偏差小于3%,直肠V_(40Gy)偏差差异最大。左右股骨头三维γ通过率最高,脊髓差异波动最大。实测、重建点剂量偏差大都与剂量偏差呈中等强度相关,二维γ通过率与各器官剂量偏差未发现明显相关,各病例靶区三维γ通过率与自身及IDV D_(50)%偏差间存在极强相关,其余相关性强弱无规律。结论基于γ和DVH评估均能一定程度揭示剂量误差,但均存在一定局限,临床中应将两者联合应用。Objective To evaluate the volumetric modulated arc therapy(VMAT)dose verification of cervical cancer based on γ rule and dose volume histogram(DVH)and to perform correlation analysis between the evaluation results and the dose differences.Methods Twenty cervical cancer VMAT plans were selected and performed on TrueBeam Linac.The delivered point and surface dose was measured by FC-65G and ArcCheck and the results were compared to those calculated by Eclipse.The dose of patients was reconstructed by 3DVH.Then,differences between the reconstructed and plan value of D_(mean),D_(95%),D_(98%) and D_(2%) of PTV,V_(20Gy) of left and right femoral head,V_(40Gy) of rectum,D1cm^(3) of cord,D_(98%),D_(2%) and D_(50%) of the 50% prescription iso-dose volume(IDV),were evaluated and 3-dimensional(3D)γ was assessed for each organ.Lastly,Pearson’s correlation coefficient was used to analyze the relationship between point dose difference,2D γ pass-rate(γ%),γ_(mean) and 3D γ% of each organ and the dose difference.Results Small differences were found between the point dose measured,reconstructed and the plan value.Differences between Dmean of PTV,all dose parameters of IDV and plan values were all within 3% and V40Gy of rectum showed the largest difference.As for the 3D γ%,the maximum pass rate was found for the left and right femoral head and the maximum variance for cord D1cm3.There was a moderate correlation between measured and reconstructed point dose deviation and dose difference of each organ,while no significant correlation was found for 2D γ%.Strong correlation was found between 3D γ% of target and D50% of PTV/IDV and no correlation was found for other organs.Conclusion The performance of both γ-and DVH-based evaluation can reveal dose error for dose verification,but both of them have some limitations and should be combined in clinical practice.

关 键 词：剂量体积直方图 伽马法则 剂量验证 容积调强弧形治疗 

分 类 号：R737.33[医药卫生—肿瘤]