宫颈癌术后调强计划的最优子野数目选择

The selection of optimal number of sub-field of postoperative intensity modulated plan for cervical cancer

目的:通过比较不同子野数目的宫颈癌术后静态调强放射治疗(IMRT)调强计划,分析临床靶区和危及器官的剂量学参数,选择最优化子野数目。方法:选取20例宫颈癌术后患者的定位影像,制作7野调强放射治疗计划。保持射野入射角度及优化目标参数相同,将子野数目分别改变为20个、30个、40个和50个,为每例患者制定4种IMRT计划。采用统计学分析方法,比较各种计划对靶区剂量学的均匀性、适形度和剂量覆盖数据,以及危及器官受照射剂量和计划机器跳数的差异。结果:4种IMRT计划的计划靶区均匀性指数、适形度指数、最大受量、膀胱V_40和小肠D_(2cc)指标比较,其差异均有统计学意义(F=3.434,F=6.071,F=4.279,F=6.335,F=3.283;P<0.05),20个子野的计划明显劣于其他计划;而机器跳数随子野数目增多而增加。结论:宫颈癌术后静态调强计划使用30个子野能在保证计划质量的同时,有效减少机器跳数,可为临床放射治疗用提供参考依据。

Objective: To analyze dosimetric parameters of clinical target volume(CTV) and organ at risk(OAR) and choose optimal number of sub-field through compared postoperatively static intensity modulated radiotherapy plan among different number of sub-field. Methods: The location images of 20 postoperative patients with cervical cancer were selected to formulate intensity modulated radiotherapy pan with 7 field. Kept the incident angle and optimal target parameter were same, the 4 kinds of schemes were designed for each patient through changed the number of subfield to 20, 30, 40 and 50. The statistic analysis was adopted to compare the differences of these data of homogeneity, conformation level, dose coverage of various plan for dosimetry of target region, and the radiation dosage of OAR and monitor unit of plan. Results: The differences of heterogeneity index(HI), conformity level index, Dmax of PTV, V40 of bladder and D2cc of small intestine among 4 target volumes were significant(F=3.434, F=6.071, F=4.279, F=6.335, F=3.283, P<0.05). The plan of 20 sub-fields was significantly inferior to others, while the increase of MU was with the increasing of the number of sub-field. Conclusion: Using 30 sub-fields in the postoperative IMRT of cervical carcinoma can ensure the quality of plan, at the same time, it can effectively reduce MU and provide reference for clinical application.