X-rays are also called roentgen rays. It is a short-wave electromagnetic radiation with a wavelength of (20 ~ 0.06) × 10-8 cm. Roentgen rays have strong penetrating ability, and can penetrate many substances that are opaque to visible light, such as ink paper and wood. This invisible ray can make many solid substances emit visible fluorescence, make the photographic film sensitive and ionize the air. The shorter the wavelength, the greater the energy of X-rays, which is called hard X-rays. The longer the wavelength, the lower the energy, which is called soft X-rays. When high-speed electrons bombard a metal target in vacuum, the target emits X-rays, which is the structural principle of an X-ray tube. The emitted X-rays can be divided into two categories: (1) If the electron energy blocked by the target does not exceed a certain limit, only continuous spectrum radiation is emitted. This kind of radiation is called bremsstrahlung; (2) a discontinuous, it only has a few special linear spectrum, this kind of emission linear spectrum radiation is called characteristic radiation. The properties of continuous spectrum have nothing to do with the target material, while the characteristic spectrum has something to do with the target material. Different materials have different characteristic spectra, which is why they are called "characteristics". X-rays are characterized by short wavelength and high frequency. Therefore, X-rays must be produced by atomic transition between two energy levels with very different energy levels. Therefore, the innermost electron of an atom emits X-ray spectrum when it transitions, and the outer electron emits spectrum when it transitions. X-rays will not deflect in electric and magnetic fields. This shows that X-rays are uncharged particle streams. 1906 experiment proves that X-ray is an electromagnetic wave with short wavelength, so it can produce interference and diffraction phenomena. X-rays are used to help people with medical diagnosis and treatment; Used for the inspection of nondestructive materials in industry; In the fields of basic science and applied science, X-ray spectroscopy and X-ray absorption are widely used in crystal structure analysis, chemical analysis and atomic structure research.

In order to make a definite diagnosis, clinicians often need patients to go to the radiology department for various examinations, such as fluoroscopy, radiography, barium meal in digestive tract, special radiography and so on. So patients often ask radiologists questions of one kind or another, and the most common question is: Do these tests have a great impact on my health? Answering this question is not a simple sentence, it should be treated according to the specific situation.

Let's talk about the basic principle of X-ray. X-ray was discovered by German physicist Roentgen William Conrad on1895165438+1October 8th. At that time, because people didn't understand this kind of ray, they gave it an unknown name "X", and later people called it "X-ray". X-rays are really harmful to human health. The greater the X-ray exposure, the greater the damage to human health. X-ray irradiation can accumulate in the body, and its main harm is that it has certain lethality to white blood cells in human blood components, which reduces the number of white blood cells in human blood, and then leads to the decline of immune function of the body, which is easy to make bacteria invade the body and cause diseases. According to the principle of X-ray theory, the patient's safe exposure should be within 100 roentgen during X-ray examination, and the allowable exposure times and time should be determined according to this exposure. For example, chest fluoroscopy should not exceed 12 minutes in a few days, and gastrointestinal examination should not exceed 10 minutes. As for the photo inspection, because the exposure is different in different parts, the corresponding allowable exposure times are also different. The influence of patients doing 2 ~ 3 times a year on their health can be ignored. Moreover, with the continuous development of medical images, green screen and green film are used in films and clips at present, which reduces the X-ray irradiation dose by 1/2 compared with the original dose, which further protects the health of patients and does not reduce the diagnosis effect at all. In addition, in recent years, major hospitals have adopted the method of taking photos as the main method, supplemented by perspective. On the one hand, it can reduce patients' excessive intake of X-rays (fluoroscopy is larger than X-rays taken), on the other hand, it can provide basis for the diagnosis of diseases and facilitate treatment and review and comparison.

Although X-ray examination is safe for most people, it should be emphasized that pregnant women, infants and children should try to avoid X-ray examination because they are very sensitive to X-rays. If examination is needed, especially pelvic measurement or fetal examination, the exposure times shall not exceed 2 ~ 3 times. X-ray examination of infants and young children is best to expose only the examination site and cover the rest. In general, it should be relatively safe if it does not exceed the allowed irradiation time and times. But everyone's sensitivity to X-rays is different, and it is also related to the general health of the human body. More importantly, the so-called safe exposure dose does not guarantee that it is also safe for genetic factors, because it is not clear how much exposure dose is enough to affect heredity. However, from the point of view of prevention, the fewer X-rays, the better.