床转角对宫颈癌非共面调强放疗计划的影响

Effect of couch rotation angle on non-coplanar intensity modulation plan for cervical cancer

目的:探讨床转角对宫颈癌非共面调强放疗(intensity-modulated radiation therapy,IMRT)计划靶区和危及器官剂量的影响。方法:回顾性选取在某院肿瘤科治疗的 20 例宫颈癌术后患者的病例资料,基于 Eclipse v13.6 计划系统,为每位患者制订一个 7 野共面 IMRT 计划(床转角为 0°),再改变部分射野角度下的床转角为 315°~355°和 5°~45°,每隔 10°设计一个非共面 IMRT 计划(共 10 个)。比较 2 种 IMRT 计划的靶区剂量学参数和膀胱、直肠、小肠、左右股骨头和骨盆等危及器官的剂量学参数。采用 SPSS 22.0 软件进行统计学分析。结果:非共面 IMRT 计划与共面IMRT 计划的靶区剂量学参数均无显著差异(P>0.05)。非共面 IMRT 计划的膀胱 V_(30)、V_(40),直肠 V_(30)、V_(40)与共面 IMRT计划相比无统计学差异(P>0.05),除床转角为 345°外,其他床转角的非共面 IMRT 计划的小肠 D_(1 cc)比共面 IMRT 计划高(P<0.05);床转角为 315°和 325°的非共面 IMRT 计划左股骨头 V_(20)、V_(30)、D_(mean)和右股骨头 V_(20)比共面 IMRT 计划右股骨头低(P<0.05),床转角为 35°和 45°的非共面 IMRT 计划右股骨头 V_(20)比共面 IMRT 计划低,床转角为 25°、35°和 45°的非共面 IMRT 计划右股骨头 D_(mean)比共面 IMRT 计划低(P<0.05);床转角为 315°的非共面 IMRT 计划骨盆V_(10)和 D_(mean)比共面 IMRT 计划低(P<0.05),床转角为 45°的非共面 IMRT 计划骨盆 V_(10)比共面 IMRT 计划低(P<0.05)。结论:不同床转角的非共面 IMRT 计划对靶区剂量无显著影响,但对左右股骨头和骨盆的受量会有不同程度的影响,建议制订宫颈癌非共面 IMRT 计划时床转角选取 315°或者 45°。

Objective To investigate the effects of the couch rotation angle on the planning target volume and organs at risk of non-coplanar intensity-modulated radiation therapy(IMRT)for cervical cancer.Methods Totally 20 postoperative patients with cervical cancer treated in the oncology department of a hospital were selected retrospectively.A 7-field coplanar IMRT plan with the couch rotation angle being 0°was formulated for each patient with Eclipse v13.6 treatment planning system.The couch rotation angles with specific gantry angles were changed to 315°to 355°and 5°to 45°,and a non-coplanar IMRT plan(10 plans in total)was established every 10°.The dosimetry parameters of the two kinds of IMRT plans were compared for the target volumes and organs at risk such as bladder,tectum,small intestine,left and right femoral heads and pelvis.SPSS 22.0 software was used for statistical analysis.Results There were no significant differences between the target volume parameters of the coplanar and non-coplanar IMRT plans(P>0.05);the non-coplanar IMRT plans had no statistical differences in V_(30) and V_(40) values of bladder and rectum when compared with the coplanar IMRT plans(P>0.05);the values of the small intestine D_(1 cc) of the non-coplanar IMRT plans were obviously higher than those of the coplanar IMRT plans in case the couch rotation angle was not 345°(P<0.05);the values of the left femoral head V_(20),V_(30),D_(mean) and right femoral head V_(20) in the non-coplanar IMRT plans with 315°and 325°couch rotation angles were lower than those in the coplanar IMRT plans(P<0.05),the values of the right femoral head V_(20) in the non-coplanar IMRT plans with 35°and 45°couch rotation angles were lower than those in the coplanar IMRT plans,and the right femoral head D_(mean) values in the non-coplanar IMRT plans with 25°,35°and 45°couch rotation angles were lower than those in the coplanar IMRT plans(P<0.05);the values of the pelvis V_(10) and D_(mean) in the non-coplanar IMRT plans with 315°couch rotation angle were lower than those in the coplanar IMRT plans(P<0.05),and the values of the pelvis V_(10) in the non-coplanar IMRT plans with 45°couch rotation angle were lower than those in the coplanar IMRT plans(P<0.05).Conclusion The non-coplanar plans with different couch rotation angles have no significant effects on the dose of the target volume,while affects the doses to the left and right femoral heads and pelvis to some extent.It's suggested the couch rotation angle be 315°or 45°when developing a non-coplanar IMRT plan for cervical cancer patients.