As an important imaging examination, CT has unparalleled advantages for the detection of certain diseases, such as acute cerebral infarction, cerebral hemorrhage, head trauma and lung lesions.
Especially with the pandemic of the new crown and various respiratory viruses, the number of lung CT scans may be much more than in recent years!
But recently, a study published in Nature showed that even at low doses, CT scans increased the risk of certain malignancies. What's going on?
1. Do 1 more CT time
This cancer has a 43% increased risk
The study, published in Nature Medicine, collected data from more than 940,000 children and adolescents from nine countries, who cumulatively underwent more than 1.33 million CT scans, an average of 1.52 per patient.
After an average follow-up of about 7.8 years, 790 cases of hematologic malignancies were recorded, including 578 cases of malignant lymphoma and 203 cases of myeloid malignancies and acute leukemia.
The results showed that an increased relative risk of all hematologic malignancies was observed at a radiation dose of ≥ 10 mGy and a 166% increase in the risk of all hematologic malignancies at a radiation dose ≥ 50 mGy.
According to the analysis, with each additional CT scan, the overall risk of developing hematologic malignancies increased by 43%, the risk of lymphoid malignancies increased by 42%, and the risk of bone marrow malignancies and AL increased by 48%.
In fact, similar investigations and studies are not unique, as pointed out in the "Research Progress on Carcinogenic Risk Assessment of Children's CT Scans" published in the second issue of the Chinese Journal of Radiation Medicine and Protection in 2020 that the most common radiation tumors in children and adolescents are mainly leukemia and brain tumors.
The paper concludes that while the medical benefits of CT scans in children are undeniable, epidemiological studies have consistently and proportionally corresponded to the increased risk of leukemia and brain tumors in children exposed to CT scans.
Therefore, reducing unnecessary CT scans and lowering the dose of radiation in children is essential to reduce the risk of leukemia and brain tumors in children.
【Caution】
These findings are not intended to cause panic, but rather to remind us that the use of radiation in the medical field is a double-edged sword. It can be a powerful tool or a potential carcinogenic killer, and it is important not to take it lightly even for low-dose CT tests, especially for adolescents, and the dose needs to be adjusted reasonably to minimize radiation-related risks.
[Radiation comparison of several common examinations]
- B-ultrasound: no radiation
Ultrasonography uses sound wave reflection and no radiation.
B-ultrasound mainly screens for lesions in the abdominal cavity and pelvic organs.
- Magnetic resonance imaging (MRI): No radiation
Magnetic resonance is a man-made magnetic field that uses electromagnetic signals to image without radiation.
MRI can be done in many areas, including the brain, blood vessels, muscles, ligaments, spine, etc., but it is recommended to do MRI if you are symptomatic or advised by your doctor.
- X光：辐射很小(0.1mSv)
The principle is to use X-rays to penetrate the body and form an image, similar to taking a photograph.
It is mainly used to take chest X-rays during daily physical examinations to screen for lung diseases.
- CT：辐射较高(2-15 mSv)
CT scans also use rays to penetrate the body, but compared to X-rays, more subtle lesions can be seen.
CT is most commonly used to examine diseases of the head, chest, abdomen, and spine.
Second, the risk of CT radiation is relatively high
How many times a year can I do it?
Since the cumulative damage of CT radiation should not be underestimated, how many times a year is it relatively safe to do it?
Epidemiological statistical studies have shown that when the human body receives acute radiation at a time of less than 100 mSv, the definitive effect on the human body cannot be observed in medicine, that is, obvious tissue damage.
The radiation dose of common medical CT examination is:
1次低剂量螺旋CT，约为1mSv
1次头颅CT扫描，约为2mSv
1 chest CT scan, about 3mSv
1次腹部或盆腔CT，约为10mSv
Therefore, if the maximum limit of abdominal or pelvic CT is calculated, adults should do no more than 10 CT times a year, which is a relatively safe range.
If you want to be more secure and try to stay away from the potential threat of cancer, then it is safer to have a single-digit mSv per year. It can be converted to: 10 low-dose spiral CT, 5 head CT, 3 chest CT, and 1 abdominal or pelvic CT.
In addition, according to the recommendations of the American College of Radiology, the number of imaging examinations that an adult can accept in his lifetime is: 50 CT tests for the head, 66 low-dose chest CT tests for physical examination, 5000 chest X-rays, 18 chest CT tests, and 12 CT tests for the abdomen.
【Expert Reminder】
It is worth noting that for high-risk groups and patients, if CT examination is performed for the purpose of clarifying diagnosis or guiding treatment, patients should fully trust and cooperate with the doctor to conduct the examination, and should not refuse the examination because of fear of radiation and miss the opportunity for early diagnosis.
For healthy people, it is necessary to be cautious to do this kind of examination, especially PET-CT, which is not only expensive, but also has a large radiation dose, which is mainly used for diagnosis and monitoring of cancer patients, and is not recommended for healthy people.
[4 types of people should pay more attention to the number of times they do CT]
Although the cumulative dose of ionizing radiation is associated with cancer risk as a random effect, there are 4 groups of people who receive the same cumulative dose of ionizing radiation who may have a higher risk of cancer!
A study published in the journal European Radiology evaluated the risk of multiple radiological tests to induce cancer and found that 4 groups of people were at higher risk:
(1) People with congenital diseases;
(2) people suffering from genitourinary diseases;
(3) people with digestive diseases;
(4) People with oncological diseases
3. These common items around you
may mitigate radiation hazards
What should you do when you inevitably need a CT scan?
In fact, we can also help alleviate the potential harm caused by radiation by regularly consuming the following foods in our daily lives.
1. Tea
Tea polyphenols in tea have antioxidant properties, which can protect cells from oxidative damage caused by radiation, and can also intervene in apoptosis signaling pathways, inhibit abnormal apoptosis, and maintain the health of tissues.
The content of tea polyphenols varies from tea to tea, and the content of green tea, white tea, and oolong tea is generally higher.
2. Foods containing glutathione
Glutathione is a sulfur-containing amino acid that also neutralizes free radicals and reduces oxidative stress caused by radiation, and is also involved in repairing DNA damage and reducing the formation of abnormal cells, thereby reducing the risk of disease.
Animal meats such as beef, pork, and chicken, as well as nuts such as almonds and walnuts, contain a certain amount of glutathione.
In addition, foods rich in vitamin C (such as winter dates, sea buckthorn, kiwifruit, green peppers, Chinese cabbage, etc.) can help promote the production and regeneration of glutathione in the body, and vegetables rich in sulfate (such as onions, garlic, artichokes, spinach, etc.) can provide raw materials for the synthesis of glutathione in the body.
3. Cruciferous vegetables such as white radish
Radiation can damage DNA and induce cancer. And a blockbuster study published in Science by scientists from Harvard University showed that indole-3-carbinol (I3C), which is rich in white radish, can inhibit the growth of tumors.
Under normal circumstances, eating no more than 400mg of I3C per day is enough, and basically one pound of white radish is up to the standard.
Other cruciferous vegetables, such as cauliflower, kale, Chinese cabbage, cabbage, etc., also contain I3C, which can be eaten more appropriately every day.
Today's review
Have you taken a serious look at the test: which common examination has relatively high radiation?
Come and leave your answer in the comment area~