鼻咽癌调强常用布野方案剂量学比较

目的:分析在鼻咽癌逆向调强(IMRT)中两组鼻咽癌患者,用均匀9野、7野及7野非共面调强在相同条件下的剂量学差异。方法:选取28例鼻咽癌病例,分成两组,其中9野调强14例,7野调强14例,对其分别采用各自组中相同的物理调强参数,在TPS上计算需对比的设野方案计划,然后试图探讨相同计划下不同设野对靶区和重要器官的影响。结果:两组病患调强结果显示,非共面7野的靶区的最高剂量要稍大于9野,最小剂量要低于9野,7野的适形度要略差于9野,但两者差异几乎不明显,对于危及器官,9野与7野没有明显差异,在统计意义上没有显著意义。结论:对于鼻咽癌肿瘤病人,9野和7野调强在各自的条件约束下都能完成较好的计划,靶区适形度和靶区覆盖率也相差不大,综合考虑物理及生物效应,对于靶区较大的病患建议使用9野调强,对于需要特别保护晶体,7野非共面计划比较合理,对于较小肿瘤用7野照射计划相对效益更高,但总的来说照射野角度的不同对计划的影响并没有想象中那么明显,物理优化条件的好坏几乎决定了计划本身的质量。

Dosimetric Comparison of Typical Different External Beam Irradiation Techniques in Intensity Modulated Radiation Therapy Plans for Nasopharnx Carcinoma

Objective： To find the optimal beam arrangement for NPC treatment with intensity modulated radiation therapy（IMRT） technique through comparisons of 9 beam with coplanar and 7 beam with coplanar or non-coplanar arrangements in two group of the NPC’s patients with the same physical conditions.Methods： Selected 28 patients with Nasopharynx Carcinoma,cut into two group,14 patients with the physical condition of seven fields in non-coplanar technique;another 14 patient with the physical condition of nine fields in coplanar technique;We used the same condition to optimize all the plans in each group.We compared the plan,try to the influence of the important organ in different machine beam angle in same physical optimal conditions.Results： In two group IMRT’s plans are all showed,the max dose of the 7 field with the non-coplanar technique is a litter greater than the 9 field with the same surface technique,the min dose of 7 field with non-coplanar is a little lower than the dose of coplanar plan.There were not obvious differences in brain stem,spinal cord etc.among the plans of different beam’s technique.And there was also little difference in the dose distribution and conformity to the target among the plans in each of groups.All the plan’s compared results are no statistical mean.Conclusions： Different beam arrangements with the appropriate references of the physical conditions can provide desirable dose distribution for Nasopharynx Carcinoma,whatever the 7 field or 9 field.Consider the biological effects of tissues for the dose,if the targets is bigger,suggest the 9 field,it can provide the fitted conformal.7 field plan can fit all most of the tumor,it also can provide the lower MU and times than 9 field.The influence that the different angle of beam effect the plan is not obvious in our image,the fitting of optimal physical condition is much better important than the angle setting of beams.