Therapeutic ionizing radiation has been associated with cancer. Radiation is divided into two kinds: non-ionizing radiation and ionizing radiation. The former includes radiation generated by cell phones, computers and other electrical appliances, and this kind of radiation is not harmful to the human body. Therapeutic ionizing radiation, on the other hand, belongs to the latter, including X-rays, radiation therapy for tumors, etc. This kind of radiation will destroy the chemical bonds between molecules, leading to changes in molecular properties, increasing the probability of gene mutation and ultimately inducing cancer. Although therapeutic ionizing radiation is associated with the occurrence of cancer, to a certain extent, the human body caused harm, but the damage is based on a certain amount, only exceed the threshold will damage the human body, so there is no need to be overly concerned about it, only need to do a good job of the specified protective measures.