体电子密度对术后宫颈癌放射治疗计划剂量精确度的影响研究  

The effect of bulk electron density on the dose accuracy of treatment planning for postoperative cervical cancer

作　　者：韩胜[1] 彭小东[1] 袁珂 尹如铁 廖雄飞 王先良 张磊[1] 刘敏 毕斌 陈亚正 Han Sheng;Peng Xiaodong;Yuan Ke;Yin Rutie;Liao Xiongfei;Wang Xianliang;Zhang Lei;Liu Min;Bi Bin;Chen Yazheng(Department of Radiation Oncology,Chengdu Second People Hospital,Chengdu 610017,China;Sichuan Cancer Hospital&Institute,Sichuan Cancer Center,School of Medicine,University of Electronic Science and Technology of China,Radiation Oncology Key Laboratory of Sichuan Province,Chengdu 610041,China;Department of Gynecology and Obstetrics,West China Second University Hospital,Sichuan University,Key Laboratory of Obstetrics&Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education,West China Second University Hospital,Sichuan University,Chengdu 610041,China)

机构地区：[1]成都市第二人民医院肿瘤科,610017 [2]四川省肿瘤医院·研究所,四川省癌症防治中心电子科技大学医学院放射肿瘤学四川省重点实验室,成都610041 [3]四川大学华西第二医院妇产科,西部妇幼研究院出生缺陷与相关妇儿疾病教育部重点实验室,成都610041

出　　处：《中华放射医学与防护杂志》2021年第2期140-145,共6页Chinese Journal of Radiological Medicine and Protection

基　　金：四川省科技厅社会发展重点研发计划(2020YFS0437);四川省卫生健康委员会重点课题(18ZD049)。

摘　　要：目的通过在放疗计划系统手动赋予以CT图像为基础的肿瘤组织及危及器官准确的均匀体电子密度,研究其对剂量精确性的影响。方法回顾性选取20例术后宫颈癌放疗计划,从国际辐射单位与测量委员会(ICRU)46号报告导出相应器官的体电子密度,转化为相对电子密度后植入计划系统(Monaco5.11,Sweden)的危及器官模块,包括膀胱、直肠、小肠、肾脏、脊髓、股骨头、髂骨,其他组织以人体的平均电子密度代替。原始计划为双弧容积旋转调强(360°VMAT),采用蒙特卡罗算法,计算网格为0.3 cm×0.3 cm×0.3 cm,最小子野宽度为0.6 cm。保持原始计划通量不变,重新计算剂量生成新计划。通过剂量学参数以及剂量-体积直方图(DVH)二维曲线比较两种计划的区别。结果植入体电子密度后生成的计划中(Plan_(RED)),患者绝大部分的靶区剂量参数与原始计划(Plan_(ref))之间的偏差<2%,所有靶区D_(2)、D_(98)、D_(mean)的平均偏差<0.7%,180个数据中只有2个数值在2%~3%。膀胱、直肠、小肠的V_(20)、V_(30)、D_(1 cm^(3))、D_(mean)、Plan_(ref)的平均偏差<0.6%,240个数据中有4个数值>2%。Plan_(RED)的平均跳数比Plan_(ref)高0.9%,子野总数不变。手动赋予电子密度生成的计划剂量偏高,但符合临床要求。DVH图中靶区、危及器官的二维曲线几乎完全重合。两组计划剂量参数的差异无统计学意义(P>0.05)。结论通过在计划系统中手动赋予人体电子密度来生成的术后宫颈癌计划与原始计划剂量整体偏差<2%,符合临床要求,为实现MRI直接用来进行放疗计划设计和剂量计算提供了参考。Objective To study the impact on dose accuracy for the treatment planning by manually assigning accurate electron density for CT image-based tumor tissues and organs at risk.Methods Twenty cases of retrospective postoperative cervical cancer radiotherapy plans were selected.The body electron density of the corresponding organs was derived from the ICRU 46 report and assigned in the treatment planning system(Monaco5.11,Sweden),including the bladder,rectum,intestine,kidney,spinal cord,femoral head,and ilium.The original plans were double-arc volumetric modulated arc therapy plan(360°VMAT),using Monte Carlo algorithm,the calculation grid was 0.3 cm×0.3 cm×0.3 cm,and the minimum subfield width was 0.6 cm.Keep the original plan fluence unchanged and recalculate the dose to generate a new plan.The two-dimensional dose distribution and dose-volume histogram(DVH)were used to compare the differences between the two plans.The difference was compared between the two group plans by using the dosimetry parameters and DVH two dimension curve.Results For the planning of assigning bulk electron density(Plan_(RED)),the deviation of the patient′s target dose parameters and the original plan(Plan_(ref))was<2%,and the average deviation of all target regions D_(2),D_(98),D_(mean) was<0.7%,only 2 of the 180 data were between 2%and 3%.The average deviation of V_(20),V_(30),D_(1 cm^(3)),Dmean of the bladder,rectum,and small intestine,the original Plan_(ref) was less than 0.6%,and 4 out of 240 data had values>2%.PlanRED′s average hop count was 0.9%higher than Planref,and the total number of subfields remains unchanged.The planned dose generated by manually assigning the electron density in PlanRED was higher than that in Plan_(ref),but met the clinical requirements.The two-dimensional curves of the DVH diagram for targets and OARs almost completely overlapped,and there was no obvious difference in the dose distribution diagram of the same cross section.The statistical result of all parameters showed that the difference in planned

关 键 词：体电子密度 宫颈癌 放疗计划 剂量计算 

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