子宫颈癌术后调强放疗照射野设计的探讨

Beam design in cervical cancer treatment with intensity-modulated radiation therapy

目的通过对子宫颈癌调强放疗各种布野方案的比较，探讨符合临床要求的最佳照射方案。方法对10例子宫颈癌患者采用调强治疗方案，处方剂量为46Gy，分次量为2Gy。每位患者做6个不同的治疗计划，分别为5野、7野、9野均分照射，初始入射角度选用0°和180°。分别计算比较靶区的覆盖度、均匀性、适形度各项指标。结果7野和9野的靶区适形度基本一致，7野的均匀性最好，5野靶区覆盖度也能达到要求，但适形度和均匀度都次于7、9野；9野IMRT计划与5野IMRT计划相比没有减少正常组织的受照剂量，但增加了子野数和照射的总跳数，延长了治疗时间。结论在子宫颈癌的调强放疗中，综合考虑各种物理和生物因素，建议在设计照射野时尽量选择7野照射。

Objective To find the optimal beam arrangement for clinical cervical cancer treatment with intensity modulated radiation therapy （IMRT） technique through comparison between different beam arrangements. Methods Six IMRT plans were designed for 10 patients with cervical cancer. The prescribed close was 46 Gy, while the fractionated dose was 2 Gy, and 5,7,9 equispaced beams were applied. The initial beam angle degrees were 0 and 180. The terms of target coverage, target dose uniformity, and target conformability were calculated and compared. Results The target conformabilities between 7 and 9-beam plans were identical, and dose uniformity between the two angies beams was the best in 7-beam plan. The target coverage was satisfactory in 5-beam plan, but the dose uniformity and target conformability in it were inferior to those in 7 and 9-beam plans. The close on normal tissues in 9-beam plan was not less than that in 5-beam plans, but the treatment was prolonged due to the increased segments and monitor units （MU）. Conclusions Considering the physical and biological factors during the cervical cancer treatment with IMRT, 7-beam plan would be the best choice for the beam design.