Radiation in medicine is very broad, physical examination and X-ray inspection, computed tomography (CT), nuclear medicine tests include positron emission tomography (PET) and bone scan, magnetic resonance imaging (MRI), ultrasound, etc. these technologies have become an important diagnostic tool of modern medicine, but a lot of people worried about the problem, that is, radiation carcinogenesis.
Radiation is divided into two categories, ionizing radiation and non-ionizing radiation. Ionizing radiation refers to the ability to make high-frequency ionizing radiation substances occur, this radiation can damage DNA molecules, it is possible to induce cancer. Non-ionizing radiation is low-frequency radiation, there is not enough energy directly damage DNA molecules, it is also no evidence that radiation can induce cancer.
For healthy people, the physical examination is the main exposure to radiation. In the physical examination, X-ray, computed tomography (CT), nuclear medicine tests belong to ionizing radiation, the radiation source is Zhidezhuyi. MRI, ultrasound is non-ionizing radiation, is relatively safe.
Research on ionizing radiation carcinogenesis for many reasons, mainly from high-dose radiation groups, such as the atomic bomb survivors in Japan, nuclear power plant affected by the spill, patients receiving radiotherapy and radiation accept a large number of people at work. As for the risk of low dose ionizing radiation can increase cancer, there is no clear evidence, but professional bodies and recognized scientists tend dangerous low dose ionizing radiation increases the risk of cancer, but this risk is very low, and and about the amount of radiation received. Ionizing radiation will only increase the risk of cancer, do not contribute to the growth and spread of cancer already exists.
And ionizing radiation-related tumors mainly leukemia, and a few years after receiving radiation appeared, other tumors of the lung, skin cancer, thyroid cancer, multiple myeloma, breast cancer and stomach cancer, these cancers are usually accepted radiation after 10-15 years after the emergence of cancer and receiving radiation related to the site, children are more sensitive than adults.
Ionizing radiation naturally occurring in nature, the radiation dosage units of millisievert (mSv), according to US data, the amount of people living in the US average by natural ionizing radiation per year 2-3mSv, some areas such as Colorado State higher year reached 10mSv. The so-called high-dose radiation is 200mSv above.
A chest X-ray radiation is 0.02-0.1mSv, equivalent to 2.4-10 days of natural radiation, X-ray radiation in dentistry only 0.01mSv about its possibility of cancer is negligible.
Breast cancer screening mammography (MAMMOGRAM) radiation is about 0.4mSv, research in this area there are dozens of items, including a small number of healthy women found several MAMMOGRAM inspection and inspection of high-risk groups are not compared to breast cancer 1.5-fold increased risk, high-risk groups screened and non-screened compared to risk of breast cancer increased by 2.5 times, which several studies are small, not enough to describe the problem.
The current view is that healthy people 40 years of age will not lead to annual increases risk of breast cancer, which is why the annual MAMMOGRAM screening until 45 years later because, as is the possibility of cancer many years later emerged, if after 45-50 years screened again, because people may not be able to accept this live obtained by radiation cancer age. For those with BRCA1 / BRCA2 mutations who will have to pay particular attention, because of the low dose radiation on genetic mutation big impact.
CT radioactive radiation than X-ray high 500-1100 times, head CT reach 2.6mSv, with respect to the natural radiation of the year. Body CT and achieved 10.6mSv, so only one-off occasion. After the introduction of radiation carcinogenesis factors can be found CT abuse very seriously. US National Cancer Institute (NCI) estimates that in 2007 the United States took a total of 72 million CT, resulting in 29,000 cases of cancer, so that the total incidence of cancer in the US population increased by 2%. A 2009 study considered every 400-2000 times a routine chest CT can cause one tumor.
Lung cancer screening using low dose CT, radiation is about 1.5mSv, equivalent to the amount of natural radiation for six months, although lower than the head and body CT CT radiation dose, but still very cautious about the agency, until recently recommendation smokers inspection, and not all smokers. Eligible smokers is 30-year history of smoking a pack of cigarettes per day suck (30 years multiplied by 1 pack per day, if the 2 packs of cigarettes a day for 15 years is enough), or they are still smoking, or quit smoking less than 15 years . This system more stringent standard is to weigh the pros and cons, it is determined after more good than harm to recommend low-dose CT, other populations including smokers smoking history do not meet the above criteria is not recommended annual inspection, the reason is likely to harm than good.
This cautious attitude is not negative effects of radioactivity. The radiation is a very effective diagnostic techniques, many diseases rely on this technology to the discovery and diagnosis, including tumor early diagnosis and treatment, not because of possible carcinogenicity and unworthy.
After research and analysis, FDA accepted that the probability of ionizing radiation 10mSv dying of cancer will increase 0.05%, so the amount of radiation equivalent to a abdominal CT. Provide 0.05% What is the concept? Americans lifetime chance of dying from cancer was 20%, according to an abdominal CT may become after a 20.05 percent, an increase of 2.5%, not really something. But if often according to CT, adds up, even get on, such as looking for 100 times, the probability of dying from cancer becomes 25% from 20%, an increase of 25%, this rate of increase is very significant, and more than offset some healthy habits to prevent cancer effect.
Overall, the increase in medical radiation received on cancer risk or very low, or negligible, but only if the examination can not be too frequent. Medical field is both a great gap between rich and poor and overuse, many people do not physical, while others over-physical. In the absence of the necessary conditions to do a lot of checks, received a different degree of ionizing radiation. If you do this every year, adds up, it caused the cancer risk is high.
Everything goes too far, on healthy, both physical examination can not, and do a physical examination on what projects are done, so as to ensure more good than harm.
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