鼻咽癌调强放疗中对危及器官勾画及计划优化改进的剂量学探讨

Dosimetry Study to Improve the Method of Organs At Risk(OAR) Delineations and Planning Optimization in Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma

【目的】研究不同T分期和N分期下危及器官(OAR)的剂量学分布特点,对鼻咽癌调强放射治疗中的危及器官勾画和放疗计划优化的改进进行初步探讨,找出能精简的或是在优化条件下可以改进的OAR,指导以后的放疗工作,使今后放疗计划的优化和实施更加合理有效。【方法】选取2013年6月至2014年8月期间,连续收治的148例初诊鼻咽癌患者,勾画全套的OAR,并筛选出一些有研究价值的OAR,并将它们的剂量数据进行收录汇总,采用SPSS 19.0进行统计,比较这些OAR在不同分期下剂量的平均值,找出它们与T、N分期的关系,再统计出不同分期下剂量超量情况,归纳其特点,找出可以精简的OAR或是需要改进的优化参数。【结果】与T分期相关在特定分期绝大部分患者不超量的OAR有:眼球(T1-T4),晶体(T1-T2)。与N分期相关在特定分期绝大部分患者不超量的OAR有:声门喉(N0-N3)、声门上喉(N0-N1)、下咽缩肌(N0)、气管(N0-N1)、口腔(N0-N1)、臂丛神经(N0)。其余的OAR在各个分期均存在不同程度的超量。【结论】对于眼球、晶体这些在特定分期很容易满足剂量限制的OAR,评价放疗计划时可以不做过多关注,在优化计划时,对这些OAR可以考虑给一个相对较低的权重,以降低其它OAR的优化负担。而对于中耳、内耳这些非常容易超量的OAR,则需要改进优化条件,力求满足或尽量满足其限制剂量。对于喉、臂丛神经这些在特定分期不超量且理论上能够精简的结构,我们可以尝试性地精简它们。

【Objective】 This study was aimedthe dosimetric distribution of OARs（organs at risk） for nasopharyngeal carcinoma（NPC） according to different T stages and N stages, to improve the method of OAR delineations and planning optimization in intensity modulated radiation therapy（IMRT）. 【Methods】 A total of 148 NPC patients were retrospectively included. Dose-volume data of OARs were collected and analyzed. The Average dose in different stages were compared to find the relationship between OARs and T /N stage. Then we record whether the dose of each OARs exceed the limit dose or not, and sum up the characteristics of dose with different stages. Obtained the OARs those can be retrenched or optimal parameters those need to be improved. 【Results】 Those OARs not exceeding the limit dose among the most of patients on specific T stage are ： Eyes（T1-T4） and Lens（T1-T2）; Those OARs who＇s dose will not exceed the limit dose among the most of patients on Specific N stage are ： Larynx_Glottic（N0-N3）, Larynx_Supraglottic（N0-N1）, Pharynx Const_I（N0）, Trachea（N0-N1）, Oral Cavity（N0-N1）, Brachial Plex（N0）. Other OARs have different levels of dose exceeding in each T / Nstage. 【Conclusion】 For those OARs who＇s dose not exceeding the dose limit, like eyes and lens, we could take less attention on them when we evaluate the radiotherapy treatment planning. And also we can give a lower weight to them to reduce other OAR＇s pressure during the plan optimizing. For those OARs who ＇s dose hard to meet the goal, like middle ear and inner ear, we need improve optimization conditions to meet the goal as far as possible. For those OARs who ＇s dose easy to meet the goal and could theoretically be retrenched,like larynx and brachial plexus,we can try to retrench them.