头颈部肿瘤静态调强中强度分级数的研究

目的:研究在头颈部肿瘤静态调强放疗中强度分级数对计划结果的影响,确定在临床调强放疗中最佳的强度分级参数。方法:利用商用的放疗计划系统,分别对5个临床头颈部肿瘤病例作静态调强放疗计划。在强度矩阵离散化时,设置离散化等级分别为3、4、5、6、7、8、10、15和20。比较和分析强度分级数对放疗计划结果的影响。结果:从总的趋势来看,随着强度分级数的提高,PTV的最小剂量增大,最大剂量减小,剂量标准差减小;危及器官受到的剂量照射降低;总的子野数目增加;总的机器跳数降低。结论:提高强度分级数,意味着可能提高IMRT计划的质量。综合强度分级数对PTV、OAR和治疗时间的影响,建议在计划设计时,将强度分级数控制在5~10级范围内。

The Study of the Intensity Discrete Level in the Static IMRT Plans for the Head and Neck Cancer

Objective： To study the effect and fmd the optimal parameter of the intensity discrete level in the static IMRT plans for the head and neck cancer. Methods： The static IMRT plans for five patients with head and neck cancers have been ob- tained. For every patient, nine plans with different intensity discrete levels of 3, 4, 5, 6, 7, 8, 10, 15 and 20 are obtained. The ef- fect of the intensity discrete level on the results of the treatment plans is compared and analyzed. Results： Overall, the mini- mum dose, the maximum dose and the dose standard deviation of PTV become larger, less and less respectively when the in- tensity discrete level increases. At the same time, the OAR suffers less irradiation, the total number of the segments increases and the total machine unit reduces. Conclusion： Increasing the number of the intensity discrete level may mean a better static IMRT plan. Considering the effect of the intensity discrete level on PTV, the OAR and the treatment time, the intensity discrete level range from 5 to 10 is suggested.