第22题: [单项选择]楔形板用于临床应用的主要目的是()。 A. 减少皮肤剂量,得到较理想的靶区的剂量分布 B. 对人体不均匀组织进行补偿 C. 提高百分深度量 D. 得到较理想的靶区的剂量分布 E. 降低剂量率 参考答案:D 答案解析:楔形板在临床上的应用主要是得到较理想的靶区的剂量分布,其原理为:楔形板因其两端厚度不同,对射线的吸收也不同,穿透过楔形板的射野可以在体内形成不对称的剂量分布。两个或多个使用楔形板的射野可以合成一个比较
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When was Michael’s last space mission 参考答案:(in) January 答案解析:[听力原文] 11-20
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Flight C1676 crashed and exploded in fog and rain Monday night near Taipei airport as it