How big is the radiation damage of imaging inspection

"Does a chest radiograph increase the risk of cancer?"

"Can a CT child be deformed when I am pregnant?"

"Does the cell phone emit a lot of radiation?"

A few days ago, at the second China Cancer Summit Forum hosted by the National Cancer Center, the China International Association for the Promotion of Health Care, the Cancer Hospital of the Chinese Academy of Medical Sciences, and the China Cancer Foundation, Lu Jingjing, the chief physician of the Department of Radiology of Peking Union Medical College Hospital, was right. The problem of ray damage in image inspection is explained in detail. Through her introduction, these doubts have been answered one by one.

"Why do the public panic about radiation? Because radiation is colorless and tasteless, invisible, intangible, invisible, invisible, invisible, and inaudible." Lu Jingjing said that radiation is divided into non-ionizing radiation and ionizing radiation. Non-ionizing radiation includes ultraviolet rays, visible light, infrared rays, radiofrequency pulses from microwave ovens, radio waves generated by wireless phones and radio stations, etc. As the energy of non-ionizing radiation is low, you do not need to worry too much about it. What people really need to be vigilant about is ionizing radiation with a short wavelength and high frequency. Because the energy of ionizing radiation is so high that it can open the covalent bonds of biological proteins or DNA, it will then cause tissue damage, protein denaturation, and gene mutation. Ionizing radiation includes X-rays, cosmic rays, gamma rays, and radiation for radiotherapy.

Lu Jingjing pointed out that radiation is not that terrible. Natural radionuclides can be found in the human body. At the same time, we also receive radiation from the universe and isotopes in the natural environment every day. These natural radiation sources will bring us about 2.4 mSv (millisievert, radiation dose unit authors note) of radiation every year. Therefore, our body is actually exposed to radiation all the time. Regarding the impact of radiation on the human body, Lu Jingjing said that if the radiation dose reaches 100mSv, one year of exposure will cause damage to the human body; if the radiation dose reaches 1000mSv, even if it is only a short-term exposure, people will experience symptoms such as anemia, nausea, and vomiting. ; If the radiation reaches more than 4000mSv (short-term exposure), it may cause death.

So, what is the radiation dose for imaging inspection? According to Lu Jingjing, the radiation amount of a chest X-ray is about 0.1mSv, the radiation amount of a head CT is equivalent to 20 chest X-rays, about 2mSv, and the radiation amount of a chest CT is about 7mSv. , And the radiation dose received by an abdominal and pelvic CT enhanced examination can reach 20mSv.

Many people worry that the radiation from imaging examinations will increase the risk of other diseases. In this regard, Lu Jingjing pointed out that the effects of radiation on the human body can be divided into physical effects and genetic effects. The physical effect is the influence on the individual, which includes the deterministic effect and the random effect. The deterministic effect is the effect that will inevitably appear as the dose reaches a certain level, such as radiation sickness, cataract, infertility, and deformity. Other diseases, such as cancer, are random effects. Lu Jingjing said that the cancer-causing probability of taking an X-ray film is basically negligible, and the cancer-causing probability of a CT scan is also low. However, the probability of cancer will increase as the radiation dose increases. "It's like what we said always walk by the river, how can you not wet your shoes'. So in general, we still have to reduce the number of image inspections." Lu Jingjing said.

The impact of different imaging examinations on the fetus will also vary due to the different radiation doses. According to Lu Jingjing, chest X-rays, mammography, etc. are all very low-dose examinations, and the impact of these examinations can be ignored. Women should try to avoid doing middle-dose examinations such as head and chest CT and high-dose examinations such as whole-body CT during pregnancy. So what is the recommended radiation dose for deciding whether to keep the fetus after X-ray exposure during pregnancy? Lu Jingjing said that if the fetus's self-absorbed dose exceeds 100mSv, it is recommended to terminate the pregnancy, and it is recommended to keep the fetus below this value.

"The reason why children are given so much attention to radiation is not that children are very fragile, but the impact of imaging examinations on them is a lifetime. If a child's life expectancy is 80 years old, then the imaging examination is done at the age of 10. , The impact on him will be 70 years. Some children fell from the bed, and their parents sent the children to the hospital, saying that they were very worried about the child’s brain hemorrhage, and asked for a head CT. The worries of bleeding are gone, but the impact of CT on the child has really happened." Lu Jingjing said.

Lu Jingjing believes that the basic principle of radiation protection is to do nothing. There is no absolutely safe inspection. Everyone should consider whether the benefit is greater than the price paid, and weigh it before deciding whether to accept the image inspection. "As doctors, we will also give warnings and popular science to patients and the public, explain scientifically what radiation is, the radiation dose and risks of imaging examinations, and help everyone grasp the advantages and disadvantages of receiving imaging examinations."