鼻咽癌调强治疗照射野布野方向对剂量分布的影响

Influence of dose distribution selected from different beam orientation for a nasopharyngeal carcinoma IMRT plan

目的:研究不同布野方向对5野鼻咽癌同期增量调强计划剂量分布的影响。方法:取同一病例分别从患者头部上半球、下半球和全球设5个照射野,设计调强治疗计划,分别得出其剂量分布结果,对比靶区及各主要危及器官受量。结果:靶区剂量分布差别不大;全球5野均匀分布照射时,腮腺受量明显少于其他布野方式;从下半球布野视交叉受量最少。结论:不同布野方向对5野鼻咽癌同期增量调强计划靶区剂量分布影响不大,全球5野均匀分布照射可更好地保护腮腺,当靶区距视交叉较近时推荐从下半球布野。

Purpose： To evaluate the different dose distribution created by three different plans on a nasopharyngeal carcinoma case with simultaneous integrated boost intensity modulated radiation therapy （ SIB-IMRT）. Methods： we designed three different SIB-IMRT plans on a nasopharyngeal carcinoma case, one was from anterior direction of the head, 5 non-equally spaced fields, another was from posterior direction of the head, 5 non-equally spaced fields also, third was 5 equally spaced fields around the head. Each plan had its dose distribution to the target and main critical structures. Results： No significant difference of dose distribution to the target when comparing the previous three different IMRT plans. However. dose to the parotids delivered from 5-equally spacd was obviously lower than the other plans, dose to the optic chiasm was much lower created by the plan designed from the posterior direction of the head with 5 non-equally spacea field. Conclusions： For a nasopharyngeal carcinoma case, there is no significant difference of dose distribution to the target compared with three different 5-beam orientation SIB-IMRT plans. To protect parotids, we recommend designing a plan with equal beam direction around the head. When the target is very close to the optic chiasm, plauning from posterior direction of the head should be better.