All chemical elements form isotopes with unstable nuclei that, during their half-lives, emit α particles, β particles or γ rays. Iodine has 37 types of nuclei with the same charge, but differing in the number of neutrons, which determine the mass of the nucleus and atom. The charge of all isotopes of iodine (I) is 53. When referring to an isotope with a certain number of neutrons, write this number next to the symbol, separated by a dash. In medical practice, I-124, I-131, I-123 are used. The normal isotope of iodine (not radioactive) is I-127.

The number of neutrons serves as an indicator for various diagnostic and therapeutic procedures. Radioiodine therapy is based on different half-lives of radioactive isotopes of iodine. For example, an element with 123 neutrons decays in 13 hours, with 124 in 4 days, and I-131 will be radioactive in 8 days. I-131 is most often used, the decay of which produces γ-rays, inert xenon and β-particles.

The effect of radioactive iodine in treatment

Iodine therapy is prescribed after complete removal of the thyroid gland. With partial removal or conservative treatment, this method does not make sense to use. Thyroid follicles receive iodides from the tissue fluid that washes them. Iodide enters the tissue fluid from the blood either diffusely or through active transport. During iodine starvation, secretory cells begin to actively capture radioactive iodine, and degenerated cancer cells do this much more intensely.

β-particles released during half-life kill cancer cells.

The damaging ability of β-particles acts at a distance of 600 – 2000 nm, this is quite enough to destroy only the cellular elements of malignant cells, and not neighboring tissues.

The main goal of treatment with radioiodine therapy is the final removal of all remnants of the thyroid gland, because even the most skillful operation leaves behind these remnants. Moreover, in the practice of surgeons it has already become a custom to leave several gland cells around the parathyroid glands for their normal functioning, as well as around the recurrent nerve that innervates the vocal cords. The destruction of the iodine isotope occurs not only in residual thyroid tissue, but also in metastases in cancerous tumors, which makes it easier to monitor the concentration of thyroglobulin.

γ-rays do not have a therapeutic effect, but they are successfully used in diagnosing diseases. The γ-camera built into the scanner helps determine the localization of radioactive iodine, which serves as a signal for recognizing cancer metastases. The accumulation of the isotope occurs on the surface of the front of the neck (in the place of the former thyroid gland), in the salivary glands, along the entire length of the digestive system, and in the bladder. Not many, but there are still iodine uptake receptors in the mammary glands. Scanning allows you to identify metastases in the separated and nearby organs. Most often they are found in the cervical lymph nodes, bones, lungs and mediastinal tissues.

Prescriptions for treatment with radioactive isotopes

Radioiodine therapy is indicated for use in two cases:

1. If the condition of a hypertrophied gland is detected in the form of a toxic goiter (nodular or diffuse). The condition of diffuse goiter is characterized by the production of thyroid hormones by the entire secretory tissue of the gland. In nodular goiter, only the tissue of the nodes secretes hormones. The objectives of administering radioactive iodine are reduced to suppressing the functionality of hypertrophied areas, since the radiation of β-particles destroys precisely those areas that are prone to thyrotoxicosis. At the end of the procedure, either the normal function of the gland is restored, or hypothyroidism develops, which is easily returned to normal by using an analogue of the hormone thyroxine - T4 (L-form).
2. If a malignant neoplasm of the thyroid gland (papillary or follicular cancer) is detected, the surgeon determines the degree of risk. In accordance with this, risk groups are identified according to the level of tumor progression and possible distant localization of metastases, as well as the need for treatment with radioactive iodine.
3. The low-risk group includes patients with a small tumor, not exceeding 2 cm and located within the outline of the thyroid gland. No metastases were found in neighboring organs and tissues (especially lymph nodes). These patients do not need to be given radioactive iodine.
4. Patients with average risk have a tumor more than 2 cm, but not exceeding 3 cm. If the prognosis is unfavorable and the capsule grows in the thyroid gland, a dose of radioactive iodine of 30-100 mCi is prescribed.
5. The high-risk group has a pronounced aggressive growth pattern of the cancerous tumor. There is growth into neighboring tissues and organs, lymph nodes, and there may be distant metastases. Such patients require treatment with a radioactive isotope of more than 100 millicuries.

Procedure for administering radioactive iodine

The radioactive isotope of iodine (I-131) is synthesized artificially. Used orally in the form of gelatin capsules (liquid). The capsules or liquid are odorless and tasteless and should only be swallowed with a glass of water. After drinking the liquid, it is recommended to immediately rinse your mouth with water and swallow it without spitting it out.

If you have dentures, it is better to temporarily remove them before consuming liquid iodine.

You cannot eat food for two hours; you can (even need) drink plenty of water or juice. Iodine-131, which is not absorbed by the thyroid follicles, is excreted in the urine, so urination should occur every hour with monitoring of the isotope content in the urine. Medicines for the thyroid gland are taken no earlier than after 2 days. It is better if the patient’s contact with other people during this time is strictly limited.

Before the procedure, the doctor must analyze the medications you are taking and stop them at different times: some of them a week, others at least 4 days before the procedure. If a woman is of childbearing age, then pregnancy planning will have to be postponed for a period determined by the doctor. Previous surgery requires a test to determine the presence or absence of tissue capable of absorbing iodine-131. 14 days before the start of the administration of radioactive iodine, a special diet is prescribed, in which the normal isotope of iodine-127 must be completely eliminated from the body. Your doctor will advise you on a list of products for effective iodine removal.

Treatment of cancer tumors with radioactive iodine

If an iodine-free diet is properly followed and the period of restrictions on taking hormonal medications is followed, the thyroid cells are completely cleared of iodine residues. When radioactive iodine is administered against the background of iodine starvation, cells tend to capture any isotope of iodine and are affected by β-particles. The more actively cells absorb a radioactive isotope, the more they are affected by it. The dose of irradiation to the thyroid follicles that capture iodine is several tens of times greater than the effect of the radioactive element on surrounding tissues and organs.

French experts estimate that almost 90% of patients with lung metastases survived after treatment with a radioactive isotope. The ten-year survival rate after the procedure was more than 90%. And these are patients with the last (IVc) stage of a terrible disease.

Of course, the described procedure is not a panacea, because complications after its use are not excluded.

First of all, it is sialadenitis (inflammation of the salivary glands), accompanied by swelling and pain. This disease develops in response to the introduction of iodine and the absence of thyroid cells capable of capturing it. Then the salivary gland has to take over this function. It is worth noting that sialadenitis progresses only with high doses of radiation (above 80 mCi).

There are cases of disruption of the reproductive function of the reproductive system, but with repeated irradiation, the total dose of which exceeds 500 mCi.

Treatment procedure after thyroidectomy

Cancer patients are often prescribed iodine therapy after removal of the thyroid gland. The goal of this procedure is to completely destroy the cancer cells remaining after the operation not only in the thyroid area, but also in the blood.

After taking the drug, the patient is placed in a single room, which is equipped in accordance with the specifics.

Medical personnel are limited in contact for a period of up to five days. At this time, visitors should not be allowed into the ward, especially pregnant women and children, in order to protect them from the flow of radiation particles. The patient's urine and saliva are considered radioactive and must be specially disposed of.

Pros and cons of radioactive iodine treatment

The described procedure cannot be called completely “harmless”. Thus, during the action of a radioactive isotope, temporary phenomena are observed in the form of painful sensations in the area of ​​the salivary glands, tongue, and the front of the neck. There is a dry mouth and a sore throat. The patient feels nauseous, has frequent vomiting, swelling, and food becomes unpalatable. In addition, old chronic diseases worsen, the patient becomes lethargic, gets tired quickly, and is prone to depression.

Despite the negative aspects of treatment, the use of radioactive iodine is increasingly used in the treatment of the thyroid gland in clinics.

The positive reasons for this pattern are:

• there is no surgical intervention with cosmetic consequences;
• general anesthesia is not required;
• the relative cheapness of European clinics compared to operations with high quality of service and scanning equipment.

Radiation hazard from contact

It should be remembered that the benefits provided by the use of radiation are obvious to the patient himself. For the people around him, radiation can play a cruel joke. Not to mention the patient’s visitors, let us mention that medical workers provide care only when necessary and always wear protective clothing and gloves.

After discharge, you cannot be in contact with a person closer than 1 meter, and during a long conversation you should move away 2 meters. In the same bed, even after discharge, it is not recommended to sleep in the same bed with another person for 3 days. Sexual contacts and being near a pregnant woman are strictly prohibited for a week from the date of discharge, which occurs five days after the procedure.

How to behave after irradiation with an iodine isotope?

For eight days after discharge, you should keep children away from you, especially touching them. After using the bath or toilet, flush with water three times. Hands are washed thoroughly with soap.

It is better for men to sit on the toilet when urinating to prevent splashing of radiation urine. Breastfeeding should be stopped if the patient is a nursing mother. The clothes the patient wore during treatment are placed in a bag and washed separately a month or two after discharge. Personal items are removed from common areas and storage. In the event of an emergency visit to the hospital, it is necessary to warn medical personnel about the recent completion of a course of irradiation with iodine-131.

Iodine isotope I-131 has long been successfully used in the diagnosis and treatment of thyroid diseases. But for some reason, not only among patients in our country, but also among medical workers, there are various prejudices and fears about the method of radioiodine therapy. This is due to the rare use of this treatment method in clinical practice and the lack of awareness of doctors on this issue.

What is hidden under the terrible name “radioactive iodine”?

I-131 has the ability to spontaneously disintegrate an atom. The half-life is 8 days. In this case, a neutral xenon atom, a gamma radiation quantum and a beta particle (electron) are formed. The therapeutic effect is carried out precisely thanks to beta particles. Such particles have a very high speed of movement, but a short range in tissues (up to 2 mm). Thus, they penetrate biological tissues (thyroid cells) and destroy the cell (cytotoxic effect).

Thanks to Iodine accumulates in the human body exclusively in the cells of the thyroid gland, I-131 carries out its action only here, it does not affect any other tissues.

Gamma radiation, which is formed during the radioactive decay of an iodine atom, penetrates the human body (has a long range, but little energy). Thus, it does not affect the cells of the body. But it can be used for diagnostic purposes. This way you can determine where else iodine has accumulated in the body using a special gamma camera that detects such radiation. If such foci exist, then we can think about the existence of metastases of thyroid cancer.

Radioactive iodine therapy is prescribed in 2 cases:

• with overproduction of thyroid hormones (diffuse toxic goiter, thyrotoxicosis, thyroid adenoma);
• malignant tumor of the thyroid gland (papillary and follicular cancer).

All chemical elements form isotopes with unstable nuclei that, during their half-lives, emit α particles, β particles or γ rays. Iodine has 37 types of nuclei with the same charge, but differing in the number of neutrons, which determine the mass of the nucleus and atom. The charge of all isotopes of iodine (I) is 53. When referring to an isotope with a certain number of neutrons, write this number next to the symbol, separated by a dash. In medical practice, I-124, I-131, I-123 are used. The normal isotope of iodine (not radioactive) is I-127.

The number of neutrons serves as an indicator for various diagnostic and therapeutic procedures. Radioiodine therapy is based on different half-lives of radioactive isotopes of iodine. For example, an element with 123 neutrons decays in 13 hours, with 124 in 4 days, and I-131 will be radioactive in 8 days. I-131 is most often used, the decay of which produces γ-rays, inert xenon and β-particles.

The effect of radioactive iodine in treatment

Iodine therapy is prescribed after complete removal of the thyroid gland. With partial removal or conservative treatment, this method does not make sense to use. Thyroid follicles receive iodides from the tissue fluid that washes them. Iodide enters the tissue fluid from the blood either diffusely or through active transport. During iodine starvation, secretory cells begin to actively capture radioactive iodine, and degenerated cancer cells do this much more intensely.

β-particles released during half-life kill cancer cells. The damaging ability of β-particles acts at a distance of 600 – 2000 nm, this is quite enough to destroy only the cellular elements of malignant cells, and not neighboring tissues.

The main goal of treatment with radioiodine therapy is the final removal of all remnants of the thyroid gland, because even the most skillful operation leaves behind these remnants. Moreover, in the practice of surgeons it has already become a custom to leave several gland cells around the parathyroid glands for their normal functioning, as well as around the recurrent nerve that innervates the vocal cords. The destruction of the iodine isotope occurs not only in residual thyroid tissue, but also in metastases in cancerous tumors, which makes it easier to monitor the concentration of thyroglobulin.

γ-rays do not have a therapeutic effect, but they are successfully used in diagnosing diseases. The γ-camera built into the scanner helps determine the localization of radioactive iodine, which serves as a signal for recognizing cancer metastases. The accumulation of the isotope occurs on the surface of the front of the neck (in the place of the former thyroid gland), in the salivary glands, along the entire length of the digestive system, and in the bladder. Not many, but there are still iodine uptake receptors in the mammary glands. Scanning allows you to identify metastases in the separated and nearby organs. Most often they are found in the cervical lymph nodes, bones, lungs and mediastinal tissues.

Prescriptions for treatment with radioactive isotopes

Radioiodine therapy is indicated for use in two cases:

If the condition of a hypertrophied gland is detected in the form of a toxic goiter (nodular or diffuse). The condition of diffuse goiter is characterized by the production of thyroid hormones by the entire secretory tissue of the gland. In nodular goiter, only the tissue of the nodes secretes hormones. The objectives of administering radioactive iodine are reduced to suppressing the functionality of hypertrophied areas, since the radiation of β-particles destroys precisely those areas that are prone to thyrotoxicosis. At the end of the procedure, either the normal function of the gland is restored, or hypothyroidism develops, which is easily returned to normal by using an analogue of the hormone thyroxine - T4 (L-form). If a malignant neoplasm of the thyroid gland (papillary or follicular cancer) is detected, the surgeon determines the degree of risk. In accordance with this, risk groups are identified according to the level of tumor progression and possible distant localization of metastases, as well as the need for treatment with radioactive iodine. The low-risk group includes patients with a small tumor, not exceeding 2 cm and located within the outline of the thyroid gland. No metastases were found in neighboring organs and tissues (especially lymph nodes). These patients do not need to be given radioactive iodine. Patients with average risk have a tumor more than 2 cm, but not exceeding 3 cm. If the prognosis is unfavorable and the capsule grows in the thyroid gland, a dose of radioactive iodine of 30-100 mCi is prescribed. The high-risk group has a pronounced aggressive growth pattern of the cancerous tumor. There is growth into neighboring tissues and organs, lymph nodes, and there may be distant metastases. Such patients require treatment with a radioactive isotope of more than 100 millicuries.

Procedure for administering radioactive iodine

The radioactive isotope of iodine (I-131) is synthesized artificially. Used orally in the form of gelatin capsules (liquid). The capsules or liquid are odorless and tasteless and should only be swallowed with a glass of water. After drinking the liquid, it is recommended to immediately rinse your mouth with water and swallow it without spitting it out.

If you have dentures, it is better to temporarily remove them before consuming liquid iodine.

You cannot eat food for two hours; you can (even need) drink plenty of water or juice. Iodine-131, which is not absorbed by the thyroid follicles, is excreted in the urine, so urination should occur every hour with monitoring of the isotope content in the urine. Medicines for the thyroid gland are taken no earlier than after 2 days. It is better if the patient’s contact with other people during this time is strictly limited.

Before the procedure, the doctor must analyze the medications you are taking and stop them at different times: some of them a week, others at least 4 days before the procedure. If a woman is of childbearing age, then pregnancy planning will have to be postponed for a period determined by the doctor. Previous surgery requires a test to determine the presence or absence of tissue capable of absorbing iodine-131. 14 days before the start of the administration of radioactive iodine, a special diet is prescribed, in which the normal isotope of iodine-127 must be completely eliminated from the body. Your doctor will advise you on a list of products for effective iodine removal.

Treatment of cancer tumors with radioactive iodine

If an iodine-free diet is properly followed and the period of restrictions on taking hormonal medications is followed, the thyroid cells are completely cleared of iodine residues. When radioactive iodine is administered against the background of iodine starvation, cells tend to capture any isotope of iodine and are affected by β-particles. The more actively cells absorb a radioactive isotope, the more they are affected by it. The dose of irradiation to the thyroid follicles that capture iodine is several tens of times greater than the effect of the radioactive element on surrounding tissues and organs.

The whole body is scanned after sequential radioactive iodine therapy in a patient with papillary thyroid cancer

French experts estimate that almost 90% of patients with lung metastases survived after treatment with a radioactive isotope. The ten-year survival rate after the procedure was more than 90%. And these are patients with the last (IVc) stage of a terrible disease.

Of course, the described procedure is not a panacea, because complications after its use are not excluded. First of all, it is sialadenitis (inflammation of the salivary glands), accompanied by swelling and pain. This disease develops in response to the introduction of iodine and the absence of thyroid cells capable of capturing it. Then the salivary gland has to take over this function. It is worth noting that sialadenitis progresses only with high doses of radiation (above 80 mCi).

There are cases of disruption of the reproductive function of the reproductive system, but with repeated irradiation, the total dose of which exceeds 500 mCi.

Cancer patients are often prescribed iodine therapy after removal of the thyroid gland. The goal of this procedure is to completely destroy the cancer cells remaining after the operation not only in the thyroid area, but also in the blood. After taking the drug, the patient is placed in a single room, which is equipped in accordance with the specifics.

Medical personnel are limited in contact for a period of up to five days. At this time, visitors should not be allowed into the ward, especially pregnant women and children, in order to protect them from the flow of radiation particles. The patient's urine and saliva are considered radioactive and must be specially disposed of.

Pros and cons of radioactive iodine treatment

The described procedure cannot be called completely “harmless”. Thus, during the action of a radioactive isotope, temporary phenomena are observed in the form of painful sensations in the area of ​​the salivary glands, tongue, and the front of the neck. There is a dry mouth and a sore throat. The patient feels nauseous, has frequent vomiting, swelling, and food becomes unpalatable. In addition, old chronic diseases worsen, the patient becomes lethargic, gets tired quickly, and is prone to depression.

Despite the negative aspects of treatment, the use of radioactive iodine is increasingly used in the treatment of the thyroid gland in clinics. The positive reasons for this pattern are:

there is no surgical intervention with cosmetic consequences; general anesthesia is not required; the relative cheapness of European clinics compared to operations with high quality of service and scanning equipment.

Radiation hazard from contact

It should be remembered that the benefits provided by the use of radiation are obvious to the patient himself. For the people around him, radiation can play a cruel joke. Not to mention the patient’s visitors, let us mention that medical workers provide care only when necessary and always wear protective clothing and gloves.

After discharge, you cannot be in contact with a person closer than 1 meter, and during a long conversation you should move away 2 meters. In the same bed, even after discharge, it is not recommended to sleep in the same bed with another person for 3 days. Sexual contacts and being near a pregnant woman are strictly prohibited for a week from the date of discharge, which occurs five days after the procedure.

How to behave after irradiation with an iodine isotope?

For eight days after discharge, you should keep children away from you, especially touching them. After using the bath or toilet, flush with water three times. Hands are washed thoroughly with soap. It is better for men to sit on the toilet when urinating to prevent splashing of radiation urine. Breastfeeding should be stopped if the patient is a nursing mother. The clothes the patient wore during treatment are placed in a bag and washed separately a month or two after discharge. Personal items are removed from common areas and storage. In the event of an emergency visit to the hospital, it is necessary to warn medical personnel about the recent completion of a course of irradiation with iodine-131.

Treatment with radioactive iodine is sometimes the only chance to save a person suffering from one of the forms (papillary or follicular) of differentiated thyroid cancer.

The main goal of radioiodine therapy is to destroy the follicular cells of the thyroid gland. However, not every patient can receive a referral for this type of treatment, which has a number of indications and contraindications.

What is radioiodine therapy, in what cases is it used, how to prepare for it and in which clinics can you receive treatment? All these questions can be answered in our article.

Concept of method

In radioiodine therapy, radioactive iodine is used (in medical literature it can be called iodine-131, radioiodine, I-131) - one of the thirty-seven isotopes of the well-known iodine-126, which is available in almost every first aid kit.

Having a half-life of eight days, radioiodine breaks down spontaneously in the patient's body. In this case, xenon and two types of radioactive radiation are formed: beta and gamma radiation.

The therapeutic effect of radioiodine therapy is provided by a flow of beta particles (fast electrons), which have increased penetrating ability into biological tissues located around the zone of iodine-131 accumulation due to the high emission speed. The penetration depth of beta particles is 0.5-2 mm. Since their range of action is limited only by these values, radioactive iodine works exclusively within the thyroid gland.

The equally high penetrating ability of gamma particles allows them to easily pass through any tissue of the patient’s body. To record them, high-tech equipment is used - gamma cameras. Gamma radiation, which does not produce any therapeutic effect, helps to detect localization of radioiodine accumulations.

Having scanned the patient’s body in a gamma camera, the specialist can easily identify areas of accumulation of the radioactive isotope.

This information is of great importance for the treatment of patients suffering from thyroid cancer, since the glowing foci that appear in their bodies after a course of radioiodine therapy allow us to conclude about the presence and location of metastases of the malignant neoplasm.

The main goal of treatment with radioactive iodine is the complete destruction of the tissue of the affected thyroid gland.

The therapeutic effect, which occurs two to three months after the start of therapy, is similar to the result obtained by surgical removal of this organ. Some patients may be prescribed a second course of radioiodine therapy if the pathology recurs.

Indications and contraindications

Radioiodine therapy is prescribed to treat patients suffering from:

Hyperthyroidism is a disease caused by an increased activity of the functioning of the thyroid gland, accompanied by the appearance of small benign nodular neoplasms. Thyrotoxicosis - a condition caused by an excess of thyroid hormones, which is a complication of the aforementioned disease. All types of thyroid cancer, characterized by the occurrence of malignant neoplasms in the tissues of the affected organ and accompanied by the addition of an inflammatory process. Treatment with radioactive iodine is especially necessary for patients in whose bodies distant metastases have been found that have the ability to selectively accumulate this isotope. The course of radioiodine therapy in relation to such patients is carried out only after a surgical operation to remove the affected gland. With the timely use of radioiodine therapy, most patients suffering from thyroid cancer can be completely cured.

Radioiodine therapy has proven effective in the treatment of Graves' disease, as well as nodular toxic goiter (otherwise referred to as functional autonomy of the thyroid gland). In these cases, radioactive iodine treatment is used instead of surgery.

The use of radioiodine therapy is especially justified in case of relapse of the pathology of the already operated thyroid gland. Most often, such relapses occur after operations to remove diffuse toxic goiter.

Considering the high probability of developing postoperative complications, specialists prefer to use radioiodine treatment.

An absolute contraindication to radioactive therapy is:

Pregnancy: exposure to radioactive iodine on the fetus can cause defects in its further development. The period of breastfeeding a baby. Nursing mothers taking radioactive iodine treatment need to wean their baby off the breast for quite a long time.

Pros and cons of the procedure

The use of iodine-131 (compared to surgical removal of the affected thyroid gland) has a number of advantages:

It does not involve the need to put the patient under anesthesia. Radiotherapy does not require a rehabilitation period. After treatment with an isotope, the patient's body remains unchanged: no scars and scars (inevitable after surgery) that disfigure the neck remain on it. Laryngeal edema and unpleasant sore throat that develop in a patient after taking a capsule with radioactive iodine are easily stopped with topical preparations. Radioactive radiation associated with the intake of the isotope is localized mainly in the tissues of the thyroid gland - it almost does not spread to other organs. Since reoperation for a malignant tumor of the thyroid gland can be life threatening, radioiodine therapy, which can completely stop the consequences of recurrence, is a completely safe alternative to surgery.

At the same time, radioiodine therapy has an impressive list of negative aspects:

It should not be used on pregnant women. Breastfeeding mothers are forced to stop breastfeeding their children. Given the ability of the ovaries to accumulate radioactive isotopes, you will have to protect yourself from pregnancy for six months after completion of therapy. Due to the high probability of disturbances associated with the normal production of hormones necessary for the proper development of the fetus, the birth of offspring should be planned only two years after the use of iodine-131. Hypothyroidism, which inevitably develops in patients undergoing radioiodine therapy, will require long-term treatment with hormonal drugs. After using radioiodine, there is a high probability of developing autoimmune ophthalmopathy, leading to changes in all soft tissues of the eye (including nerves, fatty tissue, muscles, synovial membranes, fatty and connective tissues). A small amount of radioactive iodine accumulates in the tissues of the mammary glands, ovaries and prostate gland. Exposure to iodine-131 can provoke a narrowing of the lacrimal and salivary glands with a subsequent change in their functioning. Radioiodine therapy can lead to significant weight gain, fibromyalgia (severe muscle pain) and unreasonable fatigue. During treatment with radioactive iodine, an exacerbation of chronic diseases may occur: gastritis, cystitis and pyelonephritis; patients often complain of changes in taste, nausea and vomiting. All these conditions are short-term and respond well to symptomatic treatment. The use of radioactive iodine increases the likelihood of developing malignant tumors of the small intestine and thyroid gland. One of the main arguments of opponents of radioactive therapy is the fact that the thyroid gland, destroyed as a result of exposure to the isotope, will be lost forever. As a counter-argument, one can make the argument that after surgical removal of this organ, its tissues also cannot be restored. Another negative factor of radioiodine therapy is associated with the need for three-day strict isolation of patients who have taken a capsule with iodine-131. Since their body then begins to emit two types (beta and gamma) of radioactive radiation, during this period the patients become dangerous to others. All clothing and items used by a patient undergoing radioiodine treatment are subject to either special treatment or disposal in compliance with radioactive protection measures.

Which is better, surgery or radioactive iodine?

Opinions on this matter are contradictory even among specialists involved in the treatment of thyroid diseases.

Some of them believe that after a thyroidectomy (surgical operation to remove the thyroid gland), a patient taking estrogen-containing drugs can lead a completely normal life, since regular intake of thyroxine can replenish the function of the missing gland without causing side effects. Proponents of radioiodine therapy focus on the fact that this type of treatment completely eliminates the side effects (the need for anesthesia, removal of the parathyroid glands, damage to the recurrent laryngeal nerve) that are inevitable during surgery. Some of them are even disingenuous, claiming that radioiodine therapy will lead to euthyroidism (normal functioning of the thyroid gland). This is an extremely erroneous statement. In fact, radioiodine therapy (as well as thyroidectomy surgery) is aimed at achieving hypothyroidism, a condition characterized by complete suppression of the thyroid gland. In this sense, both treatment methods pursue completely identical goals. The main advantages of radioiodine treatment are complete painlessness and non-invasiveness, as well as the absence of the risk of complications arising after surgery. Patients, as a rule, do not experience complications associated with exposure to radioactive iodine.

So which technique is better? In each specific case, the final word remains with the attending physician. If there are no contraindications to prescribing radioiodine therapy in a patient (suffering, for example, from Graves' disease), he will most likely advise preferring it. If the doctor believes that it is more appropriate to perform a thyroidectomy, you need to listen to his opinion.

Preparation

It is necessary to begin preparing for taking the isotope two weeks before the start of treatment.

It is advisable to prevent iodine from getting on the surface of the skin: Patients are prohibited from lubricating wounds with iodine and applying iodine mesh to the skin. Patients should avoid visiting the salt room, swimming in sea water and inhaling sea air saturated with iodine. Residents of sea coasts require isolation from the external environment for at least four days before starting therapy. Vitamin complexes, nutritional supplements and drugs containing iodine and hormones fall under a strict ban: they should be discontinued four weeks before radioiodine therapy. A week before taking radioactive iodine, all medications prescribed for the treatment of hyperthyroidism are canceled. Women of childbearing age are required to take a pregnancy test: this is necessary to eliminate the risk of pregnancy. Before the procedure for taking a capsule with radioactive iodine, a test is carried out for the absorption of radioactive iodine by the tissues of the thyroid gland. If the gland was removed surgically, an iodine sensitivity test of the lungs and lymph nodes is performed, since it is they who take on the function of accumulating iodine in such patients.

Diet before therapy

The first step in preparing a patient for radioiodine therapy is to follow a low-iodine diet aimed at reducing the iodine content in the patient's body in every possible way so that the effect of the radioactive drug will be more tangible.

Because the low-iodine diet is given two weeks prior to taking the radioactive iodine capsule, the patient is brought to a state of iodine starvation; as a result, tissues capable of absorbing iodine do so with maximum activity.

Prescribing a diet low in iodine requires an individual approach to each patient, so the recommendations of the attending physician in each case are of decisive importance.

A low-iodine diet does not mean that the patient must give up salt. You should only use a non-iodized product and limit its amount to eight grams per day. The diet is called low-iodine because the consumption of foods with low (less than 5 mcg per serving) iodine content is still allowed.

Patients undergoing radioiodine therapy should completely stop using:

Seafood (shrimp, crab sticks, sea fish, mussels, crabs, algae, seaweed and dietary supplements created on their basis). All types of dairy products (sour cream, butter, cheeses, yoghurts, dry milk porridges). Ice cream and milk chocolate (a small amount of dark chocolate and cocoa powder can be included in the patient’s diet). Salted nuts, instant coffee, chips, canned meat and fruit, French fries, oriental dishes, ketchup, salami, pizza. Dried apricots, bananas, cherries, applesauce. Iodized eggs and dishes with lots of egg yolks. This does not apply to the consumption of egg whites that do not contain iodine: during the diet you can eat them without any restrictions. Dishes and foods colored in different shades of brown, red and orange, as well as medicines containing food dyes of similar colors, since many of them may contain iodine-containing dye E127. Factory-produced bakery products containing iodine; cornflakes. Soy products (tofu cheese, sauces, soy milk) rich in iodine. Parsley and dill, leaf and watercress. Cauliflower, zucchini, persimmons, green peppers, olives, potatoes baked in their jackets.

During the period of a low-iod diet, the following is allowed:

Peanut butter, unsalted peanuts, coconuts. Sugar, honey, fruit and berry jams, jellies and syrups. Fresh apples, grapefruits and other citrus fruits, pineapples, cantaloupes, raisins, peaches (and their juices). White and brown rice. Egg noodles. Vegetable oils (except soybean). Raw and freshly cooked vegetables (except potatoes with skins, beans and soy). Frozen vegetables. Poultry (chicken, turkey). Beef, veal, lamb meat. Dried herbs, black pepper. Cereal dishes, pasta (in limited quantities). Carbonated soft drinks (lemonade, diet cola that do not contain erythrosine), tea and well-filtered coffee.

Treatment with radioactive iodine for the thyroid gland

This type of treatment is one of the highly effective procedures, the distinctive feature of which is the use of a small amount of radioactive substance, which selectively accumulates in those areas that require therapeutic action.

It has been proven that, in comparison with external beam irradiation (with a comparable exposure dosage), radioiodine therapy is capable of creating in the tissues of a tumor focus a dose of radiation that is fifty times higher than that of radiation treatment, while the effect on bone marrow cells and bone and muscle structures was tens times smaller.

The selective accumulation of a radioactive isotope and shallow penetration of beta particles into the thickness of biological structures provides the possibility of a targeted effect on the tissue of tumor foci with their subsequent destruction and complete safety in relation to adjacent organs and tissues.

How is radioiodine therapy performed? During the session, the patient receives a regular-sized gelatin capsule (odorless and tasteless), which contains radioactive iodine. The capsule should be swallowed quickly with a large amount of water (at least 400 ml).

Sometimes the patient is offered radioactive iodine in liquid form (usually in a test tube). After taking this drug, the patient will need to rinse his mouth thoroughly and then swallow the water used for this. Patients using removable dentures will be asked to remove them before the procedure.

In order for radioiodine to be better absorbed, ensuring a high therapeutic effect, the patient must refrain from eating and drinking any drinks for an hour.

After taking the capsule, radioactive iodine begins to accumulate in the tissues of the thyroid gland. If it was surgically removed, the accumulation of the isotope occurs either in the tissues remaining from it or in partially changed organs.

Radioiodine is excreted through feces, urine, secretions of the sweat and salivary glands, and the patient’s breath. That is why radiation will settle on objects surrounding the patient. All patients are warned in advance that a limited number of things should be taken to the clinic. Upon admission to the clinic, they are required to change into the hospital linen and clothing issued to them.

After taking radioiodine, patients in an isolation ward must strictly adhere to the following rules:

When brushing your teeth, avoid splashing water. The toothbrush should be rinsed thoroughly with water. When visiting the toilet, you must use the toilet carefully, avoiding splashing urine (for this reason, men should only urinate while sitting). It is necessary to wash off urine and feces at least twice, until the tank is full. Any accidental splashing of fluid or secretions should be reported to the nurse or aides. When vomiting, the patient should use a plastic bag or toilet (flush the vomit twice), but under no circumstances use a sink. It is prohibited to use reusable handkerchiefs (there must be a supply of paper ones). Used toilet paper is flushed away with the stool. The entrance door should be kept closed. Leftover food is placed in a plastic bag. Feeding birds and small animals through the window is strictly prohibited. Showering should be daily. If there is no bowel movement (it should be daily), you need to inform the nurse: the attending physician will definitely prescribe a laxative.

Visitors (especially small children and pregnant women) are not allowed to visit a patient in strict isolation. This is done in order to prevent their radiation contamination by the flow of beta and gamma particles.

Treatment procedure after thyroidectomy

Radioiodine therapy is often prescribed to cancer patients who have undergone surgery to remove the thyroid gland. The main goal of such treatment is the complete destruction of abnormal cells that could remain not only in the area where the removed organ is located, but also in the blood plasma.

The patient who has taken the drug is sent to an isolated ward, equipped taking into account the specifics of the treatment. All patient contacts with medical personnel wearing a special protective suit are limited to the most necessary procedures.

Patients treated with radioactive iodine are required to:

Increase the amount of fluid you drink to speed up the removal of iodine-131 breakdown products from the body. Shower as often as possible. Use personal hygiene items. Using the toilet, pull off the water twice. Change underwear and bedding daily. Since radiation is easily removed by washing, the patient’s clothes can be washed along with the clothes of the rest of the family. Avoid close contact with small children: pick them up and kiss them. Stay close to babies as little as possible. For three days after discharge (this occurs on the fifth day after taking the isotope), sleep only alone, separately from healthy people. It is allowed to have sexual contact, as well as to be near a pregnant woman, only a week after discharge from the clinic. If a patient who has recently undergone treatment with radioactive iodine is urgently admitted to the hospital, he is obliged to inform medical personnel about this, even if the radiation was carried out in the same clinic. All patients who have undergone radioiodine therapy will take thyroxine for life and visit the endocrinologist's office twice a year. In all other respects, their quality of life will be the same as before treatment. The above restrictions are temporary.

Consequences

Radioiodine therapy can cause certain complications:

Sialadenitis – inflammatory disease of the salivary glands, characterized by an increase in their volume, compaction and pain. The impetus for the development of the disease is the introduction of a radioactive isotope in the absence of a removed thyroid gland. In a healthy person, thyroid cells would become active in an effort to eliminate the threat and absorb radiation. In the body of the operated person, this function is taken over by the salivary glands. Progression of sialadenitis occurs only when receiving a high (above 80 millicuries - mCi) dose of radiation. Various reproductive disorders, but such a reaction of the body occurs only as a result of repeated irradiation with a total dosage exceeding 500 mCi.

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 is particularly affected by 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 its rather 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 Livingood by irradiating tellurium with a flux of deuterons and neutrons. It was subsequently discovered by Abelson among the fission products of uranium and thorium-232 atoms.

Sources of radioiodine

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

1. Nuclear power plants.
2. Pharmacological production.
3. Testing 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 number of iodine isotopes accumulate in the installations. Over 90% of the entire family of nuclides are short-lived isotopes of iodine 132-135, the rest is radioactive iodine-131. During normal operation of a nuclear power plant, the annual release of radionuclides is small due to the filtration that ensures the decay of nuclides, and is estimated by experts at 130-360 Gbq. If the seal of a nuclear reactor is breached, radioiodine, having high volatility and mobility, immediately enters the atmosphere along with other inert gases. In gas-aerosol emissions it is mostly contained in the form of various organic substances. Unlike inorganic iodine compounds, organic derivatives of the radionuclide iodine-131 pose the greatest danger to humans, since they easily penetrate through the lipid membranes of cell walls into the body and are subsequently distributed through the blood to all organs and tissues.

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

In total, two major accidents at nuclear power plants are known, which became 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 throughout the world, but the territories of Ukraine, Belarus, the southwestern regions of Russia, Finland, Germany, Sweden, and Great Britain 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. The failure of the cooling system resulted in several radiation leaks, leading to a 1,250-fold increase in the amount of iodine-131 isotopes in seawater 30 km from the nuclear power plant.

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

Biological effects of iodine-131 on humans

Radioiodine has a high migration ability, easily penetrates 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 recorded 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 thyroid tissues in higher concentrations than with reduced gland function.

Basically, iodine-131 is eliminated from the human body through 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 of it is excreted from the body this way.

Toxicity of iodine-131

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 radionuclide is considered to be one that enters the body with water and food. If the absorbed dose of radioiodine is 55 MBq/kg of body weight, acute exposure to 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, as it intensively absorbs radioactive isotopes of iodine-131 along with stable iodine.

The problem of the development of thyroid pathology also 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 consuming fresh cow's milk with a high content of radioiodine. Even measures taken by the authorities to exclude natural milk from 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!
Particularly strong irradiation of the thyroid gland occurs when dairy products are contaminated with the radionuclide iodine-131.

As a result of irradiation, the function of the thyroid gland decreases with the subsequent possible development of hypothyroidism. In this case, not only the thyroid epithelium, where hormones are synthesized, is damaged, but also the nerve cells and vessels of the thyroid gland are destroyed. The synthesis of necessary hormones sharply decreases, the endocrine status and homeostasis of the whole organism are disrupted, which can serve as the beginning of the development of thyroid cancer.

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 range 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 remain latent for a long time and appear only during intoxication, illness, or during puberty.

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

It is important to know!
In women and children, thyroid tumors occur 2-2.5 times more often 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 against toxic goiter and thyroid cancer, began to be used back in 1949. Radiotherapy is considered a relatively safe method of treatment; without it, patients are affected by various organs and tissues, the quality of life deteriorates and its duration decreases. Today, the I-131 isotope is used as an additional means to combat relapses of these diseases after surgery.

Like stable iodine, radioiodine accumulates and is retained for a long time by thyroid cells, which use it to synthesize thyroid hormones. As 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, while surrounding healthy tissues are practically not exposed to radiation.

The radioactive isotope 131 of iodine has a half-life. Radioactive isotopes produced by fission (Digest) During fission, various isotopes are formed, one might say, half of the periodic table. The probability of isotope formation varies. Some isotopes are formed with a higher probability, some with a much lower probability (see figure). Almost all of them are radioactive. However, most of them have very short half-lives (minutes or less) and decay quickly into stable isotopes. However, among them there are isotopes that, on the one hand, are readily formed during fission, and on the other, have half-lives of days and even years. They are the main danger to us. Activity, i.e. the number of decays per unit time and, accordingly, the number of “radioactive particles”, alpha and/or beta and/or gamma, is inversely proportional to the half-life. Thus, if there are the same number of isotopes, the activity of the isotope with a shorter half-life will be higher than that with a longer half-life. But the activity of an isotope with a shorter half-life will decay faster than with a longer one. Iodine-131 is formed during fission with approximately the same “hunting” as cesium-137. But iodine-131 has a half-life of “only” 8 days, and cesium-137 has a half-life of about 30 years. During the fission of uranium, at first the amount of its fission products, both iodine and cesium, increases, but soon equilibrium occurs for iodine – as much of it is formed, so much of it disintegrates. With cesium-137, due to its relatively long half-life, this equilibrium is far from achieved. Now, if there is a release of decay products into the external environment, at the initial moments, of these two isotopes, iodine-131 poses the greatest danger. Firstly, due to the peculiarities of its fission, a lot of it is formed (see figure), and secondly, due to its relatively short half-life, its activity is high. Over time (after 40 days), its activity will decrease by 32 times, and soon it will practically not be visible. But cesium-137 may not “shine” so much at first, but its activity will decrease much more slowly. Below we talk about the most “popular” isotopes that pose a danger during accidents at nuclear power plants. 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 hours; 20.8 hours; 52.6 minutes; 6.61 hours), characterized by a high yield in fission reactions, high migration ability and bioavailability. During normal operation of nuclear power plants, emissions of radionuclides, including radioisotopes of iodine, are small. In emergency conditions, as evidenced by major accidents, radioactive iodine, as a source of external and internal irradiation, was the main damaging factor in the initial period of the accident. Simplified diagram of the breakdown of iodine-131. The decay of iodine-131 produces electrons with energies up to 606 keV and gamma rays, mainly with energies of 634 and 364 keV. The main source of radioiodine for the population in areas of radionuclide contamination was local food products of plant and animal origin. A person can receive radioiodine through the following chains: plants → people, plants → animals → humans, water → hydrobionts → humans. Milk, fresh dairy products and leafy vegetables with surface contamination are usually the main source of radioiodine for the population. The absorption of the nuclide by plants from the soil, given its short lifespan, is of no practical importance. In goats and sheep, the radioiodine content in milk is several times higher than in cows. Hundredths of incoming radioiodine accumulate in animal meat. Radioiodine accumulates in significant quantities in bird eggs. The accumulation coefficients (exceeding the content in water) of 131 I in marine fish, algae, and mollusks reach 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 degrees in an adult can be expected with oral intake of 131 I in amounts of 55, 18 and 5 MBq/kg body weight. The toxicity of the radionuclide during inhalation is approximately two times higher, which is associated with a larger area of ​​contact beta irradiation. All organs and systems are involved in the pathological process, especially severe damage to the thyroid gland, where the highest doses are formed. Radiation doses to the thyroid gland in children due to its small mass when receiving the same amounts of radioiodine are significantly 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 contains much detailed information about radioactive iodine, which, in particular, may be useful to medical professionals. Radioactive cesium Radioactive cesium is one of the main dose-forming radionuclides of fission products of uranium and plutonium. The nuclide is characterized by a high migration ability in the external environment, including food chains. The main source of radiocesium for humans is food of animal and plant origin. Radioactive cesium supplied to animals with contaminated feed mainly accumulates in muscle tissue (up to 80%) and in the skeleton (10%). After the decay of radioactive isotopes of iodine, the main source of external and internal radiation is radioactive cesium. In goats and sheep, the content of radioactive cesium in milk is several times higher than in cows. It accumulates in significant quantities in bird eggs. The accumulation coefficients (exceeding 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 humans depends on the nature of the diet. Thus, 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%. Increased levels of radiocesium are recorded in residents who consume large quantities of “gifts of nature” (mushrooms, wild berries and especially game). Radiocesium, entering the body, is distributed relatively evenly, which leads to almost uniform irradiation of organs and tissues. This is facilitated by the high penetrating ability of gamma rays of its daughter nuclide 137m Ba, equal to approximately 12 cm. In the original article by I.Ya. Vasilenko, O.I. Vasilenko. Radioactive cesium contains much 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, the radioactive isotopes of which make the greatest contribution to pollution, is strontium. However, the share of strontium in irradiation is much less. Natural strontium is a trace element and consists of a mixture of four stable isotopes 84 Sr (0.56%), 86 Sr (9.96%), 87 Sr (7.02%), 88 Sr (82.0%). According to its physicochemical properties, it is an analogue of calcium. Strontium is found in all plant and animal organisms. The adult human body contains about 0.3 g of strontium. Almost all of it is in the skeleton. Under normal operating conditions of a nuclear power plant, radionuclide emissions are insignificant. They are mainly caused by gaseous radionuclides (radioactive noble gases, 14 C, tritium and iodine). During accidents, especially large ones, releases of radionuclides, including strontium radioisotopes, can be significant. 89 Sr is of greatest practical interest (T 1/2 = 50.5 days) and 90 Sr (T 1/2 = 29.1 years), characterized by high yield in 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 ytrium (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 diagram of the decay chain 90 Sr → 90 Y → 90 Zr. The decay of strontium-90 produces electrons with energies up to 546 keV, and the subsequent decay of ytrium-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 areas of nearby radionuclide fallout. However, 89 Sr has a relatively short half-life and, over time, 90 Sr begins to predominate. Animals receive radioactive strontium mainly through food and, to a lesser extent, through water (about 2%). In addition to the skeleton, the highest concentration of strontium is observed in the liver and kidneys, the minimum is in muscles and especially in fat, where the concentration is 4–6 times lower than in other soft tissues. Radioactive strontium is classified as an osteotropic biologically hazardous radionuclide. As a pure beta emitter, it poses the main danger when it enters the body. The population mainly receives the nuclide through contaminated products. The inhalation route is less important. Radiostrontium selectively deposits in bones, especially in children, exposing the bones and the bone marrow they contain to constant radiation. Everything is described in detail in the original article by I.Ya. Vasilenko, O.I. Vasilenko. Radioactive strontium.