输尿管支架在宫颈癌术后放疗中的辐射剂量学探讨

Radiation safety in patients with ureteral stent placement undergoing postoperative radiotherapy for cervical cancer

高密度植入物会对放疗剂量分布造成影响,本研究探讨放疗时安置输尿管支架的辐射安全性。收集2016年11月~2018年4月在重庆大学附属肿瘤医院安置输尿管支架行术后放疗且宫颈癌患者15例。每位患者行CT定位、靶区勾画和放疗计划设计,实际治疗组为支架组;应用密度填充技术将CT图像上输尿管支架高密度HU值替换为尿液HU值,逐个复制支架组计划,以相同优化参数设计放疗计划,为无支架组。采用蒙特卡罗方法验算两组计划,得到计划靶区(Planning target volume,PTV)和危及器官(Organs-at-risk,OARs)的γ通过率。比较两组靶区适形度指数(Conformal index,CI)、均匀性指数(Heterogeneous index,HI)和OARs受量。结果表明:两组计划γ通过率均满足临床要求;支架组与无支架组靶区CI分别为0.88±0.03和0.90±0.03(p<0.05);两组HI差异无统计学意义(p>0.05);支架组靶区D_(2%)、D_(98%)、D_(mean)和OARs受量高于无支架组,仅小肠及输尿管受量差异有统计学意义(p<0.05);输尿管支架对靶区及OARs剂量贡献率<5%。放疗时安置输尿管支架对宫颈癌术后靶区及OARs辐射剂量有一定影响,其贡献率<5%,临床影响较小,辐射相对安全。

This study aimed to investigate radiation safety in patients with ureteral stent implantation undergoing radiotherapy.We enrolled 15 patients with ureteral stents undergoing postoperative radiotherapy for cervical cancer at the Chongqing University Cancer Hospital from November 2016 to April 2018.Computed tomography localization,target delineation,and radiotherapy planning were performed.The treatment group was the stent group,and the control group was the stent-free group.The high radiodensity HU value of ureteral stents on computed tomography was replaced by liquid radiodensity using density-filling technology,and the stent-free group was optimized with the same parameters.The Monte Carlo method was used to calculate theγpassing rate of the planning target volume and organs at risk(OARs).The conformal index,homogeneity index,and OAR receiver were compared between the two groups.The results showed that theγpassing rate of both groups met the clinical requirements.The target conformal index results were 0.88±0.03 and 0.90±0.03 in the stent and stent-free groups,respectively(p<0.05).The homogeneity index result did not differ significantly between the two groups(p>0.05).D_(2%),D_(98%),D_(mean),and OARs in the stenting group were significantly higher than those in the stent-free group,and only the small intestine and ureter showed significant differences(p<0.05).The contribution rate of ureteral stents to target sites and OAR dose were<5%.In conclusion,ureter stent implantation during radiotherapy affects the postoperative target area and OAR radiation dose in patients with cervical cancer,but the contribution rate is<5%,which has little influence on clinical treatment outcome,and radiotherapy is relatively safe.