宫颈癌后装计划组织不均匀性校正对剂量计算的影响  

The effect of tissue inhomogeneity correction on the accuracy of dose calculation in brachytherapy of cervical carcinoma

作　　者：韩俊杰 顾慧宽 祁振宇[2] Han Junjie;GuHuikuan;Qi Zhenyu(Department of Radiation Oncology,Guangdong Provincial People's Hospital(Guangdong Academy of Medical Sciences),Southern Medical University,Guangzhou 510080,China;Department of Radiation Oncology,State Key Laboratory of Oncology in South China,Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy,Guangdong Provincial Clinical Research Center for Cancer,Sun Yat-sen University Cancer Center,Guangzhou 510060,China)

机构地区：[1]南方医科大学附属广东省人民医院(广东省医学科学院)放疗科,广州510080 [2]华南恶性肿瘤防治全国重点实验室,广东省鼻咽癌诊治研究重点实验室,广东省恶性肿瘤临床医学研究中心,中山大学肿瘤防治中心放疗科,广州510060

出　　处：《中华放射肿瘤学杂志》2024年第11期1049-1055,共7页Chinese Journal of Radiation Oncology

基　　金：广州市科技计划重点项目(202206010180);广东省人民医院国自然基金启动项目(1210050219)。

摘　　要：目的比较个体化蒙特卡罗(MC)模拟计算与商用治疗计划系统(TPS)剂量计算(TG43算法)的结果,探索宫颈癌后装计划组织不均匀性校正对剂量计算准确性的影响。方法利用适用于近距离放射治疗的MC代码egs_brachy构建192Ir放射源模型并验证模型的准确性。选取2022年1月至2023年5月在中山大学肿瘤防治中心已完成治疗的宫颈癌后装计划患者8例,导出其影像资料与治疗计划参数,通过自编程序在患者个体化CT图像上重建放射源驻留点的位置和驻留时间等相关计划信息,计算MC剂量分布并与TPS计算结果对比。探讨当直肠前壁充满气体时,MC模拟结果与TPS计算结果的差异。另外在MC模拟计算时分别设置5种不同的计算范围,将不同计算范围的MC模拟结果与TPS剂量分布相对比,并结合MC计算时间分析,筛选出合理的MC计算范围。利用Python中的scipy.stats库对剂量学比较结果进行独立样本t检验,比较指标包括靶区的D_(90%),以及危及器官的D_(max)、D_(mean)、D_(2 cm^(3))。结果MC模拟与TPS的计算结果对比,除直肠前壁D_(max)差异可以达到3%外,计划靶区的D_(90%),以及危及器官如膀胱、小肠的D_(mean),膀胱后壁D_(max)差异均在±1%以内。2%/2 mm标准下,γ通过率均>98%。而当直肠前壁充满气体时,相对于MC,TPS高估了直肠前壁的D_(2 cm^(3))和D_(mean),差异分别为6.06%(t=-6.80,P=0.002)和5.35%(t=-6.57,P=0.003)。均质水模体测试显示:当MC剂量计算范围与TPS剂量框一致时,会低估水中剂量分布(约4%),将MC模拟计算范围在TPS计算范围基础上外扩2 cm后,二者在均质水中剂量计算差异约为1%,计算时间较基于全域CT的MC计算节省至少8 h。结论TPS现有的TG43算法能保证宫颈癌后装计划剂量计算达到临床的基本精度要求,推荐有条件的单位采用组织不均匀校正算法进一步提高后装计算的准确性。Objective To explore the impact of tissue inhomogeneity correction on the accuracy of dose calculations in brachytherapy of cervical carcinoma by comparing the results of Monte Carlo(MC)dose simulation with those(TG43 algorithm)of treatment planning system(TPS).Methods Firstly,the 192Ir source was modeled by using a MC code specially designed for brachytherapy,called egs_brachy.The accuracy of this model was verified by comparing it with the published data.Then,8 brachytherapy plans of cervical carcinoma were selected which completed treatment at Sun Yat-sen University Cancer Center from January 2022 to May 2023,and their CT image data and treatment parameters were exported.Relevant plan information such as the source dwell positions and their corresponding dwell times were reconstructed on the patient's individualized CT images using a self-developed program.The MC dose distributions were calculated for each case and compared with the TPS calculations.When the anterior wall of the rectum was filled with gas,the differences between MC simulation and TPS calculation were compared.Additionally,5 different calculation ranges were set for MC simulation,and the MC simulation results of different calculation ranges were compared with the TPS's,combining with the time of MC simulation,a reasonable MC calculation range was comfirmed.Then,the scipy.stats library of Python was utilized to perform independent sample t-test on dosimetric comparison results,including D_(90%) of high risk clinical target volume(HR-CTV)and D_(max),D_(mean),and D_(2 cm^(3)) of organs at risk(OAR).Results The comparison between MC calculations and TPS results showed that the CTV's D_(90%),the bladder's D_(mean) and the small intestine's D_(mean) were all within ±1%,except for the D_(max) difference of approximately 3% on the anterior wall of the rectum.The 2%/2 mm gamma pass rates were all>98%.When anterior wall of the rectum filled with gas,compared with MC,TPS overestimated the anterior wall of the rectum's D_(2 cm^(3)) and D_(mean) by approxi

关 键 词：近距离放射疗法 蒙特卡罗 Egs_brachy 组织不均匀校正 放射治疗计划系统 

分 类 号：R737.33[医药卫生—肿瘤] R730.55[医药卫生—临床医学]