在肿瘤医院里，医生常常使用各种放射线来治疗癌症，这就是放射疗法，简称“放疗”。放疗的运用，至今已有90多年的历史。最早使用的放射线是x射线，后来又使用放射性同位素产生的x、β、r射线，以及各类加速器所产生的电子束、质子束、中子束、负兀介子束和重粒子束等。当放射 In the cancer hospital, doctors often use a variety of radiation to treat cancer, which is radiation therapy, referred to as “radiotherapy.” The use of radiotherapy so far has more than 90 years of history. The earliest used radiation was x-rays, and later x-, beta-, and r-rays produced by radioisotopes, as well as electron beams, proton beams, neutron beams, negative pions and heavy particle beams generated by various types of accelerators. When radiation