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目的:研究多叶准直器(MLC)漏散射线在脑转移瘤患者的放射治疗中对晶体及眼球受照剂量的影响。方法:针对10例脑转移瘤行全脑放疗的患者分别设计两种全脑放疗计划(plan1,plan2)。两种计划的机架角度相同,准直器角度分别为0°(plan1)和45°(plan2)。在处方剂量相同并保证处方剂量线包绕整个脑组织的前提下,比较两种计划的剂量体积直方图(DVH)及晶体与眼球的受照剂量。用SPSS 10.0统计学软件对每个分析指标做配对t检验,判断是否有统计学意义。结果:两种计划均满足临床要求,三维剂量分布基本一致。plan1与plan2相比,10例患者的左侧晶体的最大受照剂量平均分别为3.609和2.604 Gy(t=8.299,P<0.05),右侧晶体的最大受照剂量平均分别为3.522和2.428 Gy(t=7.567,P<0.05),左侧眼球的平均受照剂量平均分别为9.737和8.221 Gy(t=3.244,P<0.05),右侧眼球的平均受照剂量平均分别为8.390和7.148 Gy(t=3.232,P<0.05)。结论:在全脑放疗中,叶片漏散射线对晶体及眼球的受照剂量影响很大,旋转MLC可减少叶片漏散射线,显著降低晶体及眼球的受照剂量。
OBJECTIVE: To study the effect of leakage flux of multi-leaf collimator (MLC) on the dose of crystal and eyeball during radiotherapy in patients with brain metastases. Methods: Two whole brain radiotherapy plans (plan 1, plan 2) were designed for 10 patients with brain metastases undergoing whole brain radiotherapy. Both plans have the same gantry angles with collimator angles of 0 ° (plan1) and 45 ° (plan2). The two planned dose-volume histograms (DVHs) and the lens and eyeballs were compared at the same prescription dose and with the line of prescription dose wrapped around the entire brain tissue. SPSS 10.0 statistical software paired t test for each analysis of indicators to determine whether there is statistical significance. Results: Both plans met the clinical requirements and the three-dimensional dose distribution was basically the same. plan1 Compared with plan2, the maximum dose of the left lens in the 10 patients was 3.609 and 2.604 Gy (t = 8.299, P <0.05) respectively, and the average dose of the right lens was 3.522 and 2.428 Gy (t = 7.567, P <0.05). The average dose of the left eyeball averaged 9.737 and 8.221 Gy (t = 3.244, P <0.05). The mean dose of the right eyeball was 8.390 and 7.148 Gy (t = 3.232, P <0.05). CONCLUSION: In whole-brain radiotherapy, scattered radiation of leaves has a great influence on the dose of crystal and eyeball. Rotating MLC can reduce the scattered radiation of leaves and significantly reduce the dose of crystal and eyeball.