How is radioactive iodine obtained 131. How is radioactive iodine treated? Treatment with radioactive iodine

Scheme of the decay of iodine-131 (simplified)

Iodine-131 (iodine-131, 131 I), also called radioiodine(despite the presence of other radioactive isotopes of this element), is a radioactive nuclide of the chemical element iodine with atomic number 53 and mass number 131. Its half-life is about 8 days. The main application is found in medicine and pharmaceuticals. It is also one of the main products of fission of uranium and plutonium nuclei, which pose a risk to human health, which has made a significant contribution to the harmful effects on human health after nuclear tests in the 1950s, the Chernobyl accident. Iodine-131 is a significant fission product of uranium, plutonium and, indirectly, thorium, accounting for up to 3% of nuclear fission products.

Standards for the content of iodine-131

Treatment and prevention

Application in medical practice

Iodine-131, as well as some radioactive isotopes of iodine (125 I, 132 I), are used in medicine for the diagnosis and treatment of thyroid diseases. According to the radiation safety standards NRB-99/2009 adopted in Russia, discharge from the clinic of a patient treated with iodine-131 is allowed with a decrease in the total activity of this nuclide in the patient's body to a level of 0.4 GBq.

see also

Notes

Links

• Patient brochure on radioactive iodine treatment From the American Thyroid Association

Health

Concerns about exposure to radioactive substances are growing. Countries around the world are either banning or stepping up screening of imported products from earthquake-hit Japan after radioactive substances were found in food and water from nuclear power plant explosions.

The three main radioactive substances that cause concern among specialists and which have been discovered in Japan are radioactive iodine-131, radioactive cesium-134 and radioactive cesium-137.

Radioactive iodine-131

Last week, 22,000 Bq (becquerels) of radioactive iodine-131 per kilogram were found in green leafy vegetables in Japan. This level exceeds the maximum permissible level by 11 times.

Eating a kilogram of such vegetables, you get half the amount of radiation that the average person receives from the natural environment in a year.

Eating that many vegetables daily for 45 days would result in an accumulation of 50 millisieverts, the annual radiation limit that is set for a nuclear plant worker. Millisieverts express the amount of radiation absorbed by human tissues.

Impact 100 millisieverts a year increases the risk of cancer. This is the equivalent of a full body scan with three CT scans (computed tomography).

When inhaled or swallowed, iodine-131 accumulates in the thyroid gland and increases the risk of thyroid cancer. Children, fetuses in the womb and young people are especially susceptible to this effect.

The risk of thyroid cancer can be reduced by taking potassium iodide, which prevents the accumulation of radioactive iodine.

However, iodine-131 decays relatively quickly and its radioactivity is halved every 8 days. This means that it loses its effect in 80 days.

Radioactive cesium-134 and radioactive cesium-137

Vegetables in Japan have also been contaminated with 14,000 Bq of cesium per kilogram. This exceeds the allowable limit by more than 11 times.

If you eat a kilogram of such contaminated vegetables every day for a month, then this will lead to an accumulation of radiation of 20 millisieverts.

External exposure to large amounts of radioactive cesium can cause burns, acute radiation sickness and death. It may also increase the risk of cancer. Inhalation and absorption of cesium allows it to be distributed into soft tissues, especially muscle tissues, increasing the risk of cancer. It can also call spasms, involuntary muscle contractions, and infertility.

Unlike iodine, absorption of radioactive cesium cannot be prevented once a person has been exposed to it.

This substance is more of a concern than iodine-131 because it is more persistent and takes much longer to break down.

The half-life of Cesium-137 is 30 years, which means that this is how long it takes to halve its radioactivity. Requires at least 240 years for its radioactivity to be exhausted.

The half-life of Cesium-134 is 2 years, which means that it will take about 20 years for it to become harmless.

The effect of short-term and high-level exposure published by the US Environmental Protection Agency.

Unlike cancer, these effects from acute exposure tend to appear immediately, causing so-called radiation sickness, including symptoms such as nausea, hair loss, and skin burns. If a person receives a lethal dose, then death occurs within 2 months.

Exposure 50-100 millisieverts: changes in blood chemistry

Impact 500 millisievert: nausea, for several hours

Impact 700 millisievert: vomit

Impact 750 millisievert: hair loss, within 2-3 weeks

Impact 900 millisievert: diarrhea

Exposure to 1,000 millisieverts: bleeding

Impact 4,000 millisieverts: possible death within 2 months if left untreated

Exposure to 10,000 millisieverts: destruction of the intestinal mucosa, internal bleeding and death within 1-2 weeks

Impact 20,000 millisieverts: damage to the central nervous system and loss of consciousness within minutes, and death within hours or days

radioactive iodine

Among the 20 radioisotopes of iodine formed in the fission reactions of uranium and plutonium, a special place is occupied by 131-135 I (T 1/2 = 8.04 days; 2.3 h; 20.8 h; 52.6 min; 6.61 h), characterized by a high yield in fission reactions, high migratory ability and bioavailability. In the normal mode of operation of nuclear power plants, releases of radionuclides, including radioisotopes of iodine, are small. Under emergency conditions, as evidenced by major accidents, radioactive iodine, as a source of external and internal exposure, was the main damaging factor in the initial period of the accident.

Simplified scheme for the decay of iodine-131. The decay of iodine-131 produces electrons with energies up to 606 keV and gamma quanta, mainly with energies of 634 and 364 keV.

The main source of radioiodine intake for the population in the zones of radionuclide contamination was local food of plant and animal origin. A person can receive radioiodine along the chains:

• plants → human,
• plants → animals → human,
• water → hydrobionts → human.

Surface contaminated milk, fresh dairy products and leafy vegetables are usually the main source of radioiodine intake for the population. Assimilation of the nuclide by plants from the soil, given the short period of its life, is of no practical importance.

In goats and sheep, the content of radioiodine in milk is several times higher than in cows. Hundredths of incoming radioiodine accumulate in animal meat. Significant amounts of radioiodine accumulate in the eggs of birds. The coefficients of accumulation (excess over the content in water) 131 I in marine fish, algae, mollusks reaches 10, 200-500, 10-70, respectively.

The isotopes 131-135 I are of practical interest. Their toxicity is low compared to other radioisotopes, especially alpha-emitting ones. Acute radiation injuries of severe, moderate and mild degree in an adult can be expected with oral intake of 131 I in the amount of 55, 18 and 5 MBq/kg of body weight. The toxicity of the radionuclide upon inhalation intake is approximately twice as high, which is associated with a larger area of ​​contact beta irradiation.

All organs and systems are involved in the pathological process, especially severe damage in the thyroid gland, where the highest doses are formed. The doses of irradiation of the thyroid gland in children due to its small mass when receiving the same amount of radioiodine are much higher than in adults (the mass of the gland in children, depending on age, is 1: 5-7 g, in adults - 20 g).

Radioactive Iodine Radioactive iodine contains much more detailed information, which, in particular, may be useful to medical professionals.

radioactive cesium

Radioactive cesium is one of the main dose-forming radionuclides of uranium and plutonium fission products. The nuclide is characterized by high migratory ability in the environment, including food chains. The main source of radiocesium intake for humans is food of animal and vegetable origin. Radioactive cesium supplied to animals with contaminated feed accumulates mainly in muscle tissue (up to 80%) and in the skeleton (10%).

After the decay of radioactive isotopes of iodine, radioactive cesium is the main source of external and internal exposure.

In goats and sheep, the content of radioactive cesium in milk is several times higher than in cows. In significant quantities, it accumulates in the eggs of birds. The coefficients of accumulation (excess over the content in water) of 137 Cs in the muscles of fish reaches 1000 or more, in mollusks - 100-700,
crustaceans - 50-1200, aquatic plants - 100-10000.

The intake of cesium to a person depends on the nature of the diet. So after the Chernobyl accident in 1990, the contribution of various products to the average daily intake of radiocesium in the most contaminated areas of Belarus was as follows: milk - 19%, meat - 9%, fish - 0.5%, potatoes - 46%, vegetables - 7.5%, fruits and berries - 5%, bread and bakery products - 13%. An increased content of radiocesium is recorded in residents who consume large quantities of "gifts of nature" (mushrooms, wild berries, and especially game).

Radiocesium, entering the body, is relatively evenly distributed, which leads to almost uniform exposure of organs and tissues. This is facilitated by the high penetrating power of gamma quanta of its daughter nuclide 137m Ba, which is approximately 12 cm.

In the original article by I.Ya. Vasilenko, O.I. Vasilenko. Radioactive cesium contains much more detailed information about radioactive cesium, which, in particular, may be useful to medical professionals.

radioactive strontium

After the radioactive isotopes of iodine and cesium, the next most important element whose radioactive isotopes contribute the most to pollution is strontium. However, the share of strontium in irradiation is much smaller.

Natural strontium belongs to microelements and consists of a mixture of four stable isotopes 84Sr (0.56%), 86Sr (9.96%), 87Sr (7.02%), 88Sr (82.0%). According to the physicochemical properties, it is an analogue of calcium. Strontium is found in all plant and animal organisms. The body of an adult contains about 0.3 g of strontium. Almost all of it is in the skeleton.

Under the conditions of normal operation of nuclear power plants, releases of radionuclides are insignificant. They are mainly due to gaseous radionuclides (radioactive noble gases, 14 C, tritium and iodine). Under conditions of accidents, especially large ones, releases of radionuclides, including strontium radioisotopes, can be significant.

Of greatest practical interest are 89 Sr (T 1/2 = 50.5 days) and 90 Sr (T 1/2 = 29.1 years), characterized by a high yield in the fission reactions of uranium and plutonium. Both 89 Sr and 90 Sr are beta emitters. The decay of 89 Sr produces a stable isotope of yttrium ( 89 Y). The decay of 90 Sr produces beta-active 90 Y, which in turn decays to form a stable isotope of zirconium (90 Zr).

C scheme of the decay chain 90 Sr → 90 Y → 90 Zr. The decay of strontium-90 produces electrons with energies up to 546 keV; the subsequent decay of yttrium-90 produces electrons with energies up to 2.28 MeV.

In the initial period, 89 Sr is one of the components of environmental pollution in the zones of near fallout of radionuclides. However, 89 Sr has a relatively short half-life and over time 90 Sr begins to predominate.

Animals receive radioactive strontium mainly with food and, to a lesser extent, with water (about 2%). In addition to the skeleton, the highest concentration of strontium was noted in the liver and kidneys, the minimum - in the muscles and especially in fat, where the concentration is 4-6 times lower than in other soft tissues.

Radioactive strontium belongs to osteotropic biologically hazardous radionuclides. As a pure beta emitter, it poses the main danger when it enters the body. The nuclide is mainly supplied to the population with contaminated products. The inhalation route is less important. Radiostrontium is selectively deposited in the bones, especially in children, exposing the bones and the bone marrow contained in them to constant radiation.

Everything is described in detail in the original article by I.Ya. Vasilenko, O.I. Vasilenko. Radioactive strontium.

Everyone knows the high danger of radioactive iodine-131, which caused a lot of trouble after the accidents in Chernobyl and Fukushima-1. Even minimal doses of this radionuclide cause mutations and cell death in the human body, but the thyroid gland suffers especially from it. The beta and gamma particles formed during its decay are concentrated in its tissues, causing severe radiation and the formation of cancerous tumors.

Radioactive iodine: what is it?

Iodine-131 is a radioactive isotope of ordinary iodine, called "radioiodine". Due to a fairly long half-life (8.04 days), it quickly spreads over large areas, causing radiation contamination of soil and vegetation. I-131 radioiodine was first isolated in 1938 by Seaborg and Livinggood by irradiating tellurium with a stream of deuterons and neutrons. Subsequently, Abelson discovered it among the fission products of the atoms of uranium and thorium-232.

Sources of radioiodine

Radioactive iodine-131 is not found in nature and enters the environment from man-made sources:

1. Nuclear power plants.
2. Pharmaceutical production.
3. Tests of atomic weapons.

The technological cycle of any power or industrial nuclear reactor includes the fission of uranium or plutonium atoms, during which a large amount of iodine isotopes accumulate in the plants. Over 90% of the entire family of nuclides are short-lived isotopes of iodine 132-135, the rest is radioactive iodine-131. During the normal operation of a nuclear power plant, the annual release of radionuclides is small due to filtration, which ensures the decay of nuclides, and is estimated by experts at 130-360 Gbq. If there is a violation of the tightness of a nuclear reactor, radioiodine, having high volatility and mobility, immediately enters the atmosphere along with other inert gases. In the gas and aerosol emission, it is mostly contained in the form of various organic substances. Unlike inorganic iodine compounds, organic derivatives of the iodine-131 radionuclide pose the greatest danger to humans, since they easily penetrate the lipid membranes of cell walls into the body and are subsequently carried with blood to all organs and tissues.

Major accidents that have become a source of iodine-131 contamination

In total, there are two major accidents at nuclear power plants that have become sources of radioiodine contamination of large areas - Chernobyl and Fukushima-1. During the Chernobyl disaster, all the iodine-131 accumulated in the nuclear reactor was released into the environment along with the explosion, which led to radiation contamination of a zone with a radius of 30 kilometers. Strong winds and rains carried radiation around the world, but the territories of Ukraine, Belarus, the southwestern regions of Russia, Finland, Germany, Sweden, and the UK were especially affected.

In Japan, explosions at the first, second, third reactors and the fourth power unit of the Fukushima-1 nuclear power plant occurred after a strong earthquake. As a result of the violation of the cooling system, several radiation leaks occurred, leading to a 1250-fold increase in the number of iodine-131 isotopes in sea water at a distance of 30 km from the nuclear power plant.

Another source of radioiodine is nuclear weapons testing. So, in the 50-60s of the twentieth century, explosions of nuclear bombs and shells were carried out in the state of Nevada in the United States. Scientists noticed that I-131 formed as a result of explosions fell out in the nearest areas, and it was practically absent in semi-global and global fallouts due to a short half-life. That is, during the migrations, the radionuclide had time to decompose before falling along with precipitation to the Earth's surface.

Biological effects of iodine-131 on humans

Radioiodine has a high migration ability, easily enters the human body with air, food and water, and also enters through the skin, wounds and burns. At the same time, it is quickly absorbed into the blood: after an hour, 80-90% of the radionuclide is absorbed. Most of it is absorbed by the thyroid gland, which does not distinguish stable iodine from its radioactive isotopes, and the smallest part is absorbed by muscles and bones.

By the end of the day, up to 30% of the total incoming radionuclide is fixed in the thyroid gland, and the accumulation process directly depends on the functioning of the organ. If hypothyroidism is observed, then radioiodine is absorbed more intensively and accumulates in the tissues of the thyroid gland in higher concentrations than with reduced gland function.

Basically, iodine-131 is excreted from the human body with the help of the kidneys within 7 days, only a small part of it is removed along with sweat and hair. It is known that it evaporates through the lungs, but it is still not known how much is excreted from the body in this way.

Iodine-131 toxicity

Iodine-131 is a source of dangerous β- and γ-irradiation in a ratio of 9:1, capable of causing both mild and severe radiation injuries. Moreover, the most dangerous is the radionuclide that enters the body with water and food. If the absorbed dose of radioiodine is 55 MBq/kg of body weight, acute exposure of the whole body occurs. This is due to the large area of ​​beta-irradiation, which causes a pathological process in all organs and tissues. The thyroid gland is especially severely damaged, intensively absorbing radioactive isotopes of iodine-131 together with stable iodine.

The problem of the development of thyroid pathology became relevant during the accident at the Chernobyl nuclear power plant, when the population was exposed to I-131. People received large doses of radiation not only by inhaling contaminated air, but also by drinking fresh cow's milk with a high content of radioiodine. Even the measures taken by the authorities to exclude natural milk from the sale did not solve the problem, since about a third of the population continued to drink milk obtained from their own cows.

It is important to know!
Especially strong irradiation of the thyroid gland occurs when dairy products are contaminated with iodine-131 radionuclide.

As a result of radiation, the function of the thyroid gland decreases, with the subsequent possible development of hypothyroidism. This not only damages the thyroid epithelium, where hormones are synthesized, but also destroys the nerve cells and blood vessels of the thyroid gland. The synthesis of the necessary hormones is sharply reduced, the endocrine status and homeostasis of the whole organism are disturbed, which can serve as the beginning of the development of cancerous tumors of the thyroid gland.

Radioiodine is especially dangerous for children, since their thyroid glands are much smaller than those of an adult. Depending on the age of the child, the weight can be from 1.7 g to 7 g, while in an adult it is about 20 grams. Another feature is that radiation damage to the endocrine gland can be latent for a long time and manifest itself only during intoxication, illness, or during puberty.

A high risk of developing thyroid cancer occurs in children under one year of age who have received a high dose of irradiation with the isotope I-131. Moreover, the high aggressiveness of tumors has been precisely established - within 2-3 months, cancer cells penetrate into the surrounding tissues and blood vessels, metastasize to the lymph nodes of the neck and lungs.

It is important to know!
Thyroid tumors are 2-2.5 times more common in women and children than in men. The latent period of their development, depending on the dose of radioiodine received by a person, can reach 25 years or more, in children this period is much shorter - on average, about 10 years.

"Useful" iodine-131

Radioiodine, as a remedy for toxic goiter and cancerous tumors of the thyroid gland, began to be used as early as 1949. Radiotherapy is considered a relatively safe method of treatment; without it, various organs and tissues are affected in patients, the quality of life worsens and its duration decreases. Today, the I-131 isotope is used as an additional tool to combat the recurrence of these diseases after surgery.

Like stable iodine, radioiodine is accumulated and retained for a long time by thyroid cells, which use it for the synthesis of thyroid hormones. Since tumors continue to perform a hormone-forming function, they accumulate iodine-131 isotopes. When they decay, they form beta particles with a range of 1-2 mm, which locally irradiate and destroy thyroid cells, and the surrounding healthy tissues are practically not exposed to radiation.

Lydia Lyushukova

I-131 is radioactive iodine, more correctly, an isotope of iodine synthesized artificially. Its half-life is 8 hours, at which time 2 types of radiation are formed - beta and gamma radiation. The substance is absolutely colorless and tasteless, has no aroma.

When does a substance provide health benefits?

In medicine, it is used to treat the following diseases:

• hyperthyroidism - a disease caused by increased activity of the thyroid gland, in which small nodular benign formations are formed in it;
• thyrotoxicosis - a complication of hyperthyroidism;
• diffuse toxic goiter;
• thyroid cancer - during it, malignant tumors appear in the body of the gland, and the inflammatory process joins.

The isotope penetrates the active cells of the thyroid gland, destroying them - both healthy and diseased cells are affected. Iodine has no effect on surrounding tissues.

At this time, the function of the organ is inhibited.

An isotope is introduced into the body enclosed in a capsule - or in the form of a liquid - it all depends on the state of the gland, a one-time treatment or a course is necessary.

Pros and Cons of Radioiodine Thyroid Treatment

Isotope treatment is considered safer than surgery:

1. The patient does not need to be put under anesthesia;
2. There is no rehabilitation period;
3. Aesthetic defects do not appear on the body - scars and scars; it is especially valuable that the neck is not disfigured - for women, its appearance is of great importance.

A dose of iodine is most often injected into the body once, and if it causes an unpleasant symptom - itching in the throat and swelling, then it is easy to stop it with topical drugs.

The resulting radiation does not spread to the patient's body - it is absorbed by the only organ that is affected.

The amount of radioactive iodine depends on the disease.

In thyroid cancer, reoperation is life-threatening, and radioactive iodine treatment is the best way to stop a recurrence.

Cons and contraindications

The disadvantages of the technique are some consequences of treatment:

• Contraindications to treatment are conditions of pregnancy and lactation;
• The accumulation of the isotope occurs not only in the tissues of the gland itself - which is natural, but also in the ovaries, so you need to carefully protect yourself for 6 months after the therapeutic effect. In addition, the function of producing hormones that are necessary for the proper formation of the fetus may be impaired, so doctors warn that it is better to postpone plans for the birth of children for 1.5-2 years;
• One of the main drawbacks of the treatment is the uptake of the isotope by the mammary glands, adnexa in women, and the prostate in men. Let in small doses, but in these organs iodine accumulates;
• One of the consequences of the treatment of thyroid cancer and hyperthyroidism with radioactive iodine is hypothyroidism - this disease, caused by artificial means, is much more difficult to treat than if it were the result of a malfunction of the thyroid gland. In this case, continuous hormonal therapy may be required;
• The consequences of treatment with radioactive iodine may be a change in the function of the salivary and lacrimal glands - the I-131 isotope causes their narrowing;
• Complications can also affect the organs of vision - there is a risk of developing endocrine ophthalmopathy;
• Weight may increase, causeless fatigue and muscle pain may appear - fibromyalgia;
• Chronic diseases are exacerbated: pyelonephritis, cystitis, gastritis, vomiting and a change in taste sensations may occur. These effects are short-term, diseases are quickly stopped by conventional methods.

Opponents of the method of treating the thyroid gland with iodine largely exaggerate the negative consequences of this method.

If there is a complication - hypothyroidism, then hormonal drugs will have to be taken for life. With untreated hyperthyroidism, you have to take drugs of the opposite effect all your life in the same way, and at the same time be afraid that the nodes in the thyroid gland will become malignant.

Weight increases - if you lead an active lifestyle and eat rationally, then the weight will not increase much, but the quality of life will increase and life itself will be longer.

Fatigue, fatigue - these symptoms are inherent in all endocrine disorders, and they cannot be directly associated with the use of radioactive iodine.

After the use of the isotope, the risk of getting cancer of the small intestine and thyroid gland increases.

Unfortunately, no one is immune from the recurrence of the disease, and the possibility of an oncological process in individual organs - if there were already atypical cells in the body - is high even without the use of radioactive iodine.

A thyroid gland destroyed by radiation cannot be restored.

After surgery, the removed tissue also does not grow.

It should be noted one more feature of the treatment, which is considered a negative factor - within 3 days after taking radioactive iodine, patients must be in isolation. They pose a danger to others by emitting beta and gamma radiation.

Clothes and things that were in the ward and on the patient will need to be washed with running water in the future or destroyed.

Preparation for the procedure

Prepare to receive radioactive iodine should be in advance - as early as 10-14 days before treatment.

Start by changing your diet. Foods with a high content of iodine are removed from the diet - the cells should experience iodine hunger. But you should not completely refuse salt - it is enough to reduce its amount to 8 g per day.

If the thyroid gland is absent - it was removed, and now the disease has recurred, then the lungs and lymph nodes take over the accumulation of iodine - it is on their sensitivity that a test will be carried out - how the isotope is absorbed by the body.

It is required to abandon all medications used, including hormonal drugs - this must be done no later than 4 days before the start of treatment.