Doing this once can cause cancer risk

There has always been a claim that radioactive medical examinations such as CT scans are harmful to health, which makes many people who have heard of it but do not know the truth very resistant to such examinations.

In fact, radioactive examinations do produce radiation, but as a necessary medical measure, the radiation dose of the machine is fixed, and occasionally conducting one or two such examinations in accordance with the examination principles will not cause significant impact on health.

How much radiation does CT emit?

The unit of measurement for radiation dose is mSv. You can understand how much radiation CT emits through the following example. The dose for a 20-hour flight is 0.1mSv, the dose for a chest X-ray is about 0.2mSv, the dose for a CT scan is about 2mSv-10mSv, and the dose for a chest X-ray is about 1.1mSv.

The International Radiological Commission recommended in 1990 that the dose limit for the public due to any work and life exposure is 1mSv/year. In fact, the radiation dose received by imaging workers (workers who take X-rays or CT scans) is far more than 1mSv, but the average annual dose within 5 years does not exceed 20mSv, and the annual dose does not exceed 50mSv.

How CT can cause harm to people

X-rays are high-energy particles that disrupt cell function and metabolism when they penetrate the human body. If the dosage is not large, it will only produce short-term effects, the human body can repair itself, and the harm will be relatively small.

If the X-ray dose is high, it will damage genes and produce various harmful biological effects. Moreover, as the radiation dose increases, the probability of biological effects will also increase.

Biological effects not only include carcinogenic effects, but also include effects on hematopoiesis, reproduction, genetics, growth and development, and hormone regulation. Madame Curie, whom we all know, died of leukemia caused by long-term and excessive exposure to radioactive substances.

What is the probability of cancer caused by a CT scan?

Assuming that the human body is exposed to radiation, it takes the following process for a tumor to appear: first, the radiation causes DNA breaks in some cells. These damaged cells will undergo genetic repair, and most cells that fail the repair will end up with apoptosis. Gene mutations may occasionally occur, but the mutated cells will in most cases be eliminated by the immune system.

After being irradiated once, it is indeed not easy for normal cells to go through layers of low-probability events and become immortal cells. From animal experiments, it can be seen that unless exposed to long-term, high-dose radiation, cancer is generally unlikely to occur, and the probability of bone marrow suppression is even higher.

Madame Curie, who dealt with radioactive substances all day long, died of aplastic anemia (bone marrow suppression) because of long-term and excessive exposure to radioactive substances, which is equivalent to taking a CT scan all the time.

Risks and Benefits

CT is very suitable for detecting early lung cancer, judging cerebral hemorrhage, vascular reconstruction, and staging of malignant tumors. However, it is unnecessary to use CT to diagnose gastric ulcers or pelvic CT to diagnose uterine fibroids. Because each disease has its most suitable examination method, appropriate examinations should be used, or ultrasound examinations should be used. If the diagnosis is not clear, further examinations are needed.

When conducting CT examinations, we should strictly follow the three basic principles of basic radiation protection of the International Commission on Radiological Protection.

First, the principle of legitimacy, which requires ensuring that the application of ionizing radiation does less harm to the public than benefit;

The second is the optimization principle, which is to keep any exposure at a reasonable minimum level and avoid unnecessary exposure;

The third is the limitation principle, which ensures that the dose received by an individual does not exceed the prescribed dose limit, thereby minimizing the harm caused by radioactive examination to the examinee.

Taking the screening and early detection of lung cancer as an example, low-dose, high-resolution CT can detect early lung cancer without symptoms, which provides more opportunities for surgical resection. The benefits of early detection brought by CT to people at high risk of lung cancer outweigh the harm of a single exposure.

However, for patients with common pneumonia, it is not necessary to undergo repeated CT examinations in a short period of time. Chest X-rays and other methods can be used instead.

In short, CT examinations can be used safely when necessary. One or two examinations will not cause serious harm to the human body, but it should not be used indiscriminately or abused because it is thought to have little harm.