宫颈癌术后盆腔不同体外照射疗法的剂量学研究

目的：比较三维适形放射治疗（3DCRT ）、不同射野数目的调强适形放射治疗（IM-RT）和简化调强放射治疗（sIMRT）在宫颈癌根治术后计划靶体积（PTV）剂量分布、危及器官（OAR）保护以及机器跳数方面的差异，探讨宫颈癌术后盆腔外照射的合理方法。方法选择10例宫颈癌术后需行盆腔放疗的患者，分别制定4个野3DCRT ，5野、7野及9野IM RT ，5个野sIM RT 计划，处方剂量50 Gy ，通过分析靶区剂量分布均匀度、适形度，危及器官受照体积及机器跳数，比较5种计划的优缺点。结果5F-IM RT、7F-IM RT、9F-IM RT的PT V剂量分布均匀性好于3DCRT和sIM RT。5种放疗计划中以7F-IM RT 及9F-IM RT 靶区的适形度最优，5F-IM RT 次之，sIM RT 稍逊于 IM RT ，3DCRT最差。IM RT及sIM RT在高剂量区对小肠、膀胱及直肠的保护作用明显优于3DCRT。sIM-RT仅在20 Gy剂量水平对小肠的保护作用逊于7F-IM RT及9F-IM RT ，但对于直肠、膀胱的保护不逊于IM RT。sIM RT的机器跳数大于3DCRT ，但明显低于IM RT放疗计划。结论 sIM RT 是一种性价比较高的放疗技术，在宫颈癌术后盆腔放疗时值得推荐。

Study on the comparative dosimetry of different pelvic external irradiation in postoperative patients with cervical cancer

Objective To evaluate dose distribution of the target and protection of organ at risk （OAR） achieved with three dimensional conformal radiotherapy （3DCRT ） ,intensity-modulated radio-therapy （IMRT ） of different field number ,and simple intensity-modulated radiotherapy （sIMRT ） , and comparison of different monitor units （MU） were also included in patients with cervical cancer un-derwent radical hysterectomy and pelvic lymphadenectomy .Methods 10 high-risk patients with cervical cancer were selected ,and all of them needed pelvic radiotherapy after operation .The plans of 3DCRT （4 fields） ,IMRT （5 fields） ,IMRT （7 fields） ,IMRT （9 fields） and sIMRT （5 fields） for every pa-tient were designed ,and the prescribed dose was 50Gy .To compare the advantages and disadvantages of 5 plans by analyzing the homogeneity and conformity of dose contribution in the target ,the volume of organ at risk and monitor units were also evaluated .Results As homogeneity of PTV dose distribu-tion was concerned ,5F-IMRT ,7F-IMRT and 9F-IMRT were better than 3DCRT and sIMRT .The target conformabilities of 7F-IMRT and 9F-IMRT were the best ,5F-IMRT and sIMRT were better , 3DCRT was the normal .At high dose levels the IMRT and sIMRT plans could protect the small intes-tine ,bladder and rectum better than 3DCRT .sIMRT showed the same protection as IMRT in rectum , bladder ,and only showed lower preformance in V20 for small intestine .Monitor units of sIMRT were higher than 3DCRT ,but significantly lower than IMRT radiotherapy plans .Conclusion sIMRT is a cost-effective radiotherapy technique ,worthy of recommendation to patients with cervical cancer who need pelvic radiotherapy after operation .