When we are sick and go to the doctor, the doctor often recommends blood tests and imaging tests after asking about the medical history and examining the body. However, with the strengthening of people’s awareness of radiation safety, when we go to various medical imaging departments for examinations, we can’t help worrying about whether the examination contains radiation and the extent of radiation damage to our bodies.
Are medical imaging tests all radioactive? Which medical imaging tests have relatively large radiation and which medical imaging tests have relatively small radiation?
Before answering the above questions, we need to first understand what radiation is and the types of radiation.
What is radiation?
Microscopic particles with certain energy (such as X-rays, gamma rays, alpha particles, beta particles, neutrons, light waves, electromagnetic waves, etc.) have a certain penetrating ability, which is called radiation. According to the source of radiation, radiation can be divided into natural radiation and artificial radiation; according to the different particle energy and damage mechanism strong>, radiation can be divided into ionizing radiation and electromagnetic radiation.
Natural ionizing radiation refers to ionizing radiation that has existed since the existence of the earth, mainly including cosmic rays, crustal terrestrial radiation, and radiation emitted by natural radionuclides in nature. It can be seen that since the birth of human beings, it has been accompanied by ionizing radiation to multiply.
In addition to natural ionizing radiation exposure, we are also exposed to artificial ionizing radiation, most of which comes from medical radiation. The well-known medical imaging examinations X-ray, CT and nuclear medicine are accompanied by ionizing radiation.
What is the radiation dose for a medical examination
Taking a chest examination as an example, the exposure time of each X-ray film is about 0.2 seconds. The radiation dose is about 0.04 millisieverts (millisieverts are a measure of ionizing radiation).
X-rays are also used for chest X-ray, but the exposure time is relatively long, each time it takes 1 to 3 minutes, and the radiation dose is 0.1 to 0.8 millisieverts each time.
CT scans a certain thickness of the human body with an X-ray beam. According to the difference in the absorption rate and transmittance of X-rays by different tissues of the human body, it is measured by a detector and processed by a computer. Sectional or stereoscopic images of the examination site. The radiation dose for a CT scan of the chest is about 1 millisievert.
The radiation dose of PET/CT in nuclear medicine examination is higher than that of CT, and the radiation dose of one PET/CT is more than 1 millisievert. If multiple inspections or multiple inspections are performed, the radiation dose received by the human body will also increase accordingly.
Is medical radiation safe?
As mentioned above, natural radiation exists in our living environment, and these natural radiations are safe for human beings. Since we want to discuss whether medical radiation is safe, we can compare natural radiation with medical radiation.
Under normal circumstances, the effective dose of natural radiation received by a person in one year is 2.4 millisieverts. Since there are more cosmic rays in the sky than the ground, we will also receive more natural radiation than the ground when we take an airplane. For example, the natural radiation dose received by a round trip between Beijing and Guangzhou is about 0.015 millisieverts. F, the natural radiation dose received by a round-trip flight between Beijing and New York is about 0.05 millisieverts.
It can be seen that X-ray, CT and nuclear medicine examinations contain radiation, but the radiation dose of a single examination is not large, which is within the scope of safety permission.
Health knowledge “focus on”
In order to meet the needs of the disease, we should calmly accept various medical imaging examinations , don’t be too scared.
Is radiation-free medical imaging available?
If you are still concerned about medical radiation, there must be such a question “Is there any medical imaging examination without radiation?” Of course, Ultrasound and MRI are the same. No radiation.
Ultrasonography and MRI are completely free of ionizing radiation because the principle of examination and imaging is different from the above-mentioned X-ray, CT and nuclear medicine examinations with ionizing radiation.
Although there is no ionizing radiation, these two methods are not perfect. For example, ultrasound is not suitable for the examination of lungs and bones, and MRI is expensive and takes a long time to scan. , not suitable for emergency patients or especially critically ill patients.
So, if you really need an imaging test, the doctor will choose the appropriate test method according to your specific situation, whether it is with or without radiation, it is safe for most people of. Of course, if there are special circumstances, such as pregnant women, or if there are metal implants in the body, please explain to the doctor in advance, the doctor will consider it according to your special situation.
At the end, a digression, the ionizing radiation dose received by the residents around the nuclear power plant due to the operation of the nuclear power plant is less than 0.01 millisievert per person per year, and for each smoker, if they smoke 1 pack per day Smoke, with an annual radiation dose of about 35 millisieverts, is far greater than most medical radiation doses. After reading this, is it time for smokers to quit smoking?
Source of content:
People’s Health Publishing House published “The Truth Behind the Rumors, Doctors Have Good Words”
Editor of this book: Song Juexian of the Health Anti-Counterfeiting Squad
The author of this article: Hu Bing, The Third Affiliated Hospital of Sun Yat-sen University