Background &Objectives:It was difficult to get a good tissued ose distribution using fixed field irradiation technique in large field. But the translating scanning beam irradiation can make it.

背景与目的：用固定野技术行特大野照射时，很难得到理想的组织剂量分布，而平移扫描式照射却能做到。

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Background and objective brain irradiation is the traditional treatment for NSCLC patients with brain metastases, whereas combined with chemotherapy is the nowadays treatment direction.

背景与目的脑放疗是非小细胞肺癌脑转移的传统治疗，化疗与脑放疗的联合是近年的研究方向。

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