Radiation Therapy

The term "radiation therapy" generally refers to the use of ionizing radiation. While ionizing radiation is sometimes used in the case of an overactive thyroid, most applications are in radiation oncology. Ionizing radiation can hinder the reproduction of fast-growing cancer cells.

‘放射治疗’一词通常指使用电离辐射。虽然电离辐射有时用于治疗甲状腺功能亢进，但大多数应用均在放射肿瘤学领域。电离辐射可以抑制快速生长的癌细胞的繁殖。

Ionizing radiation, particularly x-rays and gamma rays, has proved to be a useful therapeutic ttool for the treatment of cancer. This may seem paradoxical after discussing radiation hazards and the possibility of a radiation-caused cancer, but the risk of a cancer-causing mutation is quite small and the most probable result of the interaction of radiation with a cell is that the cell will fail to reproduce. Since the basic problem with a cancer is that the cells reproduce uncontrollably, then irradiation would seem to be an excellent tool to use against it. The drawback is that there is no way to irradiate the cancer without also damaging the normal tissue surrounding it. The value of radiation therapy hinges upon our our ability to find ways to damage the cancer more than the normal tissue, or at least to limit the damage to the normal tissue so that there is no unacceptable loss of function. The ratio of cancer cells killed to normal cells killed is called the "therapeutic ratio". The effectiveness of the therapy depends upon making the therapeutic ratio as high as possible.

电离辐射，特别是X射线和伽马射线，已被证明是治疗癌症的一种有用的治疗工具。在讨论辐射危害和辐射导致癌症的可能性之后，这似乎有些矛盾，但癌症引发突变的风险相当小，而辐射与细胞相互作用的最可能结果是该细胞无法繁殖。由于癌症的基本问题是细胞不受控制地繁殖，因此辐射似乎是一种很好的对抗癌症的工具。缺点是无法在不损害周围正常组织的情况下对癌症进行辐射治疗。放射治疗的价值取决于我们能否找到方法使癌细胞受到的损害大于正常组织，或者至少限制对正常组织的损害，以避免不可接受的功能丧失。被杀死的癌细胞与被杀死的正常细胞的比例称为“治疗比”。治疗的效果取决于尽可能提高治疗比。

It has been observed that undifferentiated cells and rapidly dividing cells are more sensitive to radiation than well differentiated and slowly reproducing cells. Accordingly, radiation is observed to have a greater effect upon rapidly dividing cancer cells than upon the surrounding normal cells. However, a number of types of normal cells also rapidly reproduce and must be carefully monitored during radiation therapy; examples are the white blood cells and blood platelets. Intestinal membrane cells also reproduce rapidly.

已观察到未分化的细胞和快速分裂的细胞比分化良好且分裂缓慢的细胞对辐射更敏感。因此，辐射对快速分裂的癌细胞的影响比对周围正常细胞的影响更大。然而，一些类型的正常细胞也分裂迅速，因此在进行放射治疗时必须仔细监测；例如白细胞和血小板。肠道膜细胞也分裂迅速。