Safe dose of radiation for humans in sieverts. Radiation, background radiation and exposure standards

Instructions

Civilized countries of the world have long had programs for the destruction of nuclear weapons: the lesson of Hiroshima and Nagasaki was not in vain. But there are a lot of nuclear power plants on the planet that are in no way protected from accidents. Therefore, every person should know the symptoms of radiation sickness and the dangers.

Radiation dose is measured in two units: Sievert and Gray. The dose of effective and equivalent radiation is expressed in Sieverts, and the dose of absorbed radiation is expressed in Grays. But in terms of their values, they are practically equal and do not require conversion from one unit to another.

Radiation sickness can be acute or chronic. Acute radiation sickness develops with a single and relatively short-term exposure to a dose of more than 1 Gy. The symptoms of acute radiation sickness are as follows:

Gradual increase in temperature;

Severe vomiting;

- “dying” of the bone marrow, when it is no longer able to produce white blood cells, as a result of which the body is completely defenseless against infections;

Confusion;

Severe headaches;

Burns of the skin of a “radiation” nature, when the skin is intense and almost uniform;

The appearance of intradermal hemorrhages due to damage;

Eye damage, usually premature clouding of the lens of the eye;

Degeneration of normal tissues into connective tissue - the development of sclerotic processes in large blood vessels and in the lungs;

Genetic and teratogenic, in which the risk of having grandchildren with mutations and deformities increases many times over.

Therefore, the concept of a peaceful atom is very relative. Radiation even in small doses can lead to certain consequences.

The human body absorbs the energy of ionizing radiation, and the degree of radiation damage depends on the amount of energy absorbed. To characterize the absorbed energy of ionizing radiation per unit mass of a substance, the concept of absorbed dose is used.

Absorbed dose - this is the amount of ionizing radiation energy absorbed by the irradiated body (body tissues) and calculated per unit mass of this substance. The unit of absorbed dose in the International System of Units (SI) is the gray (Gy).

1 Gy = 1 J/kg

For evaluation, they also use a non-systemic unit - Rad. Rad - derived from the English “radiationabsorbeddoze” - absorbed dose of radiation. This is radiation in which every kilogram of mass of a substance (say, the human body) absorbs 0.01 J of energy (or 1 g of mass absorbs 100 erg).

1 Rad = 0.01 J/kg 1 Gy = 100 Rad

Exposure dose

To assess the radiation situation on the ground, in working or living quarters, caused by exposure to X-ray or gamma radiation, use exposure dose irradiation. In the SI system, the unit of exposure dose is coulomb per kilogram (1 C/kg).

In practice, a non-systemic unit is more often used - x-ray (R). 1 roentgen is a dose of x-rays (or gamma rays) at which 2.08 x 10 9 pairs of ions are formed in 1 cm 3 of air (or in 1 g of air - 1.61 x 10 12 pairs of ions).

1 P = 2.58 x 10 -3 C/kg

An absorbed dose of 1 Rad corresponds to an exposure dose approximately equal to 1 roentgen: 1 Rad = 1 R

Equivalent dose

When living organisms are irradiated, various biological effects occur, the difference between which at the same absorbed dose is explained by different types of irradiation.

To compare the biological effects caused by any ionizing radiation with the effects of X-ray and gamma radiation, the concept of equivalent dose. The SI unit of equivalent dose is the sievert (Sv). 1 Sv = 1 J/kg

There is also a non-systemic unit of equivalent dose of ionizing radiation - the rem (biological equivalent of an x-ray). 1 rem is a dose of any radiation that produces the same biological effect as 1 roentgen of x-rays or gamma radiation.

1 rem = 1 R 1 Sv = 100 rem

The coefficient showing how many times the assessed type of radiation is more biologically dangerous than X-ray or gamma radiation at the same absorbed dose is called radiation quality factor (K).

For X-ray and gamma radiation K=1.

1 Rad x K = 1 rem 1 Gy x K = 1 Sv

All other things being equal, the dose of ionizing radiation is greater, the longer the irradiation time, i.e. the dose accumulates over time. The dose per unit time is called dose rate. If we say that the exposure dose rate of gamma radiation is 1 R/h, this means that in 1 hour of irradiation a person will receive a dose equal to 1 R.

Radioactive source activity (radionuclide) is a physical quantity characterizing the number of radioactive decays per unit time. The more radioactive transformations occur per unit of time, the higher the activity. In the C system, the unit of activity is the becquerel (Bq) - the amount of radioactive substance in which 1 decay occurs in 1 second.

Another unit of radioactivity is the curie. 1 curie is the activity of such an amount of radioactive substance in which 3.7 x 10 10 decays occur per second.

The time during which the number of atoms of a given radioactive substance is reduced by half due to decay is called half-life . The half-life can vary widely: for uranium-238 (U) – 4.47 ppb. years; uranium-234 – 245 thousand years; radium-226 (Ra) – 1600 years; iodine-131 (J) – 8 days; radon-222 (Rn) – 3.823 days; polonium-214 (Po) – 0.000164 sec.

Among the long-lived isotopes released into the atmosphere as a result of the explosion of the nuclear power plant in Chernobyl, there are strontium-90 and cesium-137, the half-lives of which are about 30 years, so the Chernobyl nuclear power plant zone will be unsuitable for normal life for many decades.

RADIATION RISK COEFFICIENTS

It should be taken into account that some parts of the body (organs, tissues) are more sensitive than others: for example, with the same equivalent dose of radiation, cancer is more likely to occur in the lungs than in the thyroid gland, and irradiation of the gonads is especially dangerous due to the risk of genetic damage. Therefore, irradiation doses to organs and tissues should be taken into account with different coefficients. Taking the radiation risk coefficient of the whole organism as one, for different tissues and organs the radiation risk coefficients will be as follows:

0.03 – bone tissue;

0.03 – thyroid gland;

0.12 – light;

0.12 – red bone marrow;

0.15 – mammary gland; 0.25 – ovaries or testes;

0.30 – other fabrics.

RADIATION DOSES RECEIVED BY HUMAN

Populations in any region of the globe are exposed to ionizing radiation every day. This is, first of all, the so-called background radiation of the Earth, which consists of:

cosmic radiation coming to Earth from Space;

In addition, people encounter artificial sources of radiation, including radioactive nuclides (radionuclides), created by human hands and used in the national economy.

On average, the radiation dose from all natural sources of ionizing radiation is about 200 mR per year, although this value can vary in different regions of the globe from 50 to 1000 mR/year or more (Table 1). The dose received from cosmic radiation depends on altitude; the higher above sea level, the greater the annual dose.

Table 1

Natural sources of ionizing radiation

Artificial sources of ionizing radiation (Table 2):

medical diagnostic and treatment equipment;

people who constantly use the aircraft are additionally exposed to minor radiation;

nuclear and thermal power plants (the dose depends on the proximity of their location);

phosphate fertilizers;

Buildings made of stone, brick, concrete, wood - poor indoor ventilation can increase the radiation dose caused by inhaling the radioactive gas radon, which is formed during the natural decay of radium contained in many rocks and building materials, as well as in the soil. Radon is an invisible, tasteless and odorless heavy gas (7.5 times heavier than air), etc.

Each inhabitant of the Earth throughout his life is annually exposed to a dose of an average of 250-400 mrem.

It is considered safe for a person to accumulate a radiation dose of no more than 35 rem over his entire life. At radiation doses of 10 rem, no changes are observed in the organs and tissues of the human body. With a single irradiation dose of 25-75 rem, short-term minor changes in blood composition are clinically determined.

When irradiated with a dose of more than 100 rem, the development of radiation sickness is observed:

100 – 200 rem – I degree (light);

200 – 400 rem – II degree (average);

400 – 600 rem – III degree (severe);

more than 600 rem – IV degree (extremely severe).

A person who picks up a dosimeter for the first time suddenly discovers that it is not entirely clear what it shows... But situations can be different, and our lives may depend on how well we understand the dosimeter’s readings.

In one of the following articles we will tell you how to use a dosimeter, where to start, what to do, and what not to do. Now let's talk about what the dosimeter shows and why it may be important for us.

What indicators will be especially important to us?

Firstly, to put it simply, our accumulated dose.

In dosimetry, only indicators of the absorbed equivalent effective dose are used. It is measured in Sieverts.

The fact is that the body is capable of accumulating all the radiation absorbed during its life in the form of irreversible changes in tissues and organs, as well as radionuclides deposited in internal tissues. Since some background radiation is constantly present in nature, a person accumulates a dose of 100 to 700 mSv (millisieverts) during his life. This figure is calculated for 70 years of life. In this situation, it is not at all difficult to calculate the rate of accumulated dose received per year or per day. It turns out that under normal conditions in a year we “should” collect a norm of 1.43 - 10 mSv, and per day, respectively, 0.004 - 0.027 mSv. The accumulated dose equivalent is measured after the dosimeter is turned on and until it is turned off or until the measurement results are reset to zero.

But in some “non-standard situations” it happens that a person can catch a radiation dose that is many times higher than the natural background levels. This dose can be accumulated at a time (one-time exposure), short-term (irradiation for up to 4 days in a row) or over many years.

Radiation with small doses over a long period of time is considered much more dangerous than irradiation with a large dose over a short period of time. Perhaps due to the fact that the human body is still able to fight radiation and restore damaged tissue.

Here is a breakdown of the consequences of accumulating a particular dose.

3 mSv/year is considered an absolutely safe normal dose of background radiation.

20 mSv/year is the annual radiation dose limit for workers in nuclear and other types of radiation-hazardous work.

150 mSv/year - increases the likelihood of cancer.

250 mSv - after reaching this threshold of the accumulated dose, the liquidator of the Chernobyl accident was no longer allowed to perform dangerous work and was sent away from Chernobyl.

With short-term irradiation, the limit of the maximum permissible accumulated dose rises.

Up to 0.01 mSv - this dose can be ignored.

If during one shift a worker has a risk of exceeding the threshold of 0.2 mSv, such work is classified as radiation hazardous and requires wearing a dosimeter.

Up to 100 mSv is the permissible one-time(!) emergency exposure of the population. By medical methods, no noticeable deviations in the structure of tissues and organs are observed.

One-time exposure to more than 200 mSv is considered potentially dangerous and critical to health.

Irradiation with a dose of 500-1000 mSv causes a feeling of fatigue, and moderate changes in the composition of the blood are observed. The condition returns to normal after some time. But there is a possibility of cancer occurring in the future.

1000-1500 mSv (1-1.5 Sv) at a time can cause symptoms indicating a reaction of organs and systems - nausea, vomiting, impaired performance. Various forms of radiation sickness occur.

After doses of 1500 mSv (1.5 Sv) and higher (high levels of radiation), it is customary to measure the absorbed dose in Grays (1 Sv = 1 Gy). Obviously, the irradiated object is no longer perceived as “biological” (this is the black humor of doctors).

1.5-2.5 Gy (1500-2500 mSv) - a short-term mild form of radiation sickness is observed, which appears in the form of pronounced leukopenia (decrease in the number of leukocytes) that lasts a long time. In 30-50% of cases, vomiting may occur on the first day after irradiation. At doses greater than 2 gray, there is a high risk of death.

2.5-4 Gy (2500-4000 mSv) - radiation sickness of moderate severity occurs. All irradiated patients experience nausea and vomiting on the first day after irradiation, the leukocyte count sharply decreases, and subcutaneous hemorrhages appear. Such doses cause significant, irreparable damage to health, baldness and leukemia.

Now about something completely unpleasant. Lethal doses of penetrating radiation:

3-4 Gy (3000-4000 mSv) - bone marrow damage; within a month after irradiation, death is possible in 50% of those exposed (without medical intervention).

4-7 Gy (4000-7000 mSv) - a severe form of radiation sickness develops and mortality is high.

Article navigation:

In what units is radiation measured and what permissible doses are safe for humans. Which background radiation is natural and which is acceptable. How to convert one unit of radiation measurement to another.

Permissible doses of radiation

• permissible level of radioactive radiation from natural radiation sources, in other words, the natural radioactive background, in accordance with regulatory documents, can be present for five years in a row not higher how

  0.57 µSv/hour

In subsequent years, background radiation should not exceed  0.12 μSv/hour



• maximum permissible total annual dose received from all technogenic sources, is
  

The value of 1 mSv/year should in total include all episodes of man-made exposure to radiation on humans. This includes all types of medical examinations and procedures, including fluorography, dental x-rays, and so on. This also includes flying on airplanes, going through security at the airport, obtaining radioactive isotopes from food, and so on.

How is radiation measured?

To assess the physical properties of radioactive materials, the following quantities are used:

• radioactive source activity(Ci or Bq)
• energy flux density(W/m2)

To assess the effects of radiation on substance (not living tissue), apply:

• absorbed dose(Gray or Rad)
• exposure dose(C/kg or X-ray)

To assess the effects of radiation on living tissues, apply:

• equivalent dose(Sv or rem)
• effective equivalent dose(Sv or rem)
• equivalent dose rate(Sv/hour)

Assessment of the effect of radiation on non-living objects

The effect of radiation on a substance is manifested in the form of energy that the substance receives from radioactive radiation, and the more the substance absorbs this energy, the stronger the effect of radiation on the substance. The amount of energy of radioactive radiation affecting a substance is estimated in doses, and the amount of energy absorbed by the substance is called - absorbed dose .

Absorbed dose is the amount of radiation that is absorbed by a substance. The SI system uses - Gray (Gr).

1 Gray is the amount of radioactive radiation energy of 1 J that is absorbed by a substance weighing 1 kg, regardless of the type of radioactive radiation and its energy.

1 Gray (Gy) = 1 J/kg = 100 rad

This value does not take into account the degree of exposure (ionization) to the substance of various types of radiation. A more informative value is exposure dose of radiation.

Exposure dose is a quantity characterizing the absorbed dose of radiation and the degree of ionization of the substance. The SI system uses - Coulomb/kg (C/kg).

1 C/kg= 3.88*10 3 R

The non-systemic exposure dose unit used is X-ray (R):

1 R = 2.57976*10 -4 C/kg

Dose of 1 Roentgen- this is the formation of 2.083 * 10 9 pairs of ions per 1 cm 3 of air

Assessment of the effects of radiation on living organisms

If living tissues are irradiated with different types of radiation having the same energy, the consequences for living tissue will vary greatly depending on the type of radioactive radiation. For example, the consequences of exposure alpha radiation with an energy of 1 J per 1 kg of a substance will be very different from the effects of an energy of 1 J per 1 kg of a substance, but only gamma radiation. That is, with the same absorbed dose of radiation, but only from different types of radioactive radiation, the consequences will be different. That is, to assess the effect of radiation on a living organism, simply the concept of absorbed or exposure dose of radiation is not enough. Therefore, for living tissues the concept was introduced equivalent dose.

Equivalent dose is the dose of radiation absorbed by living tissue, multiplied by the coefficient k, which takes into account the degree of danger of various types of radiation. The SI system uses - Sievert (Sv) .

Used non-system equivalent dose unit - rem (rem) : 1 Sv = 100 rem.

The higher the “k coefficient”, the more dangerous the effect of a certain type of radiation is on the tissues of a living organism.

For a better understanding, we can define “equivalent radiation dose” a little differently:

Equivalent radiation dose - this is the amount of energy absorbed by living tissue (absorbed dose in Gray, rad or J/kg) from radioactive radiation, taking into account the degree of impact (damage) of this energy on living tissue (K coefficient).

In Russia, since the Chernobyl accident, the non-systemic unit of measurement microR/hour, reflecting exposure dose, which characterizes the measure of ionization of a substance and the dose absorbed by it. This value does not take into account the differences in the effects of different types of radiation (alpha, beta, neutron, gamma, x-ray) on a living organism

The most objective characteristic is - equivalent radiation dose, measured in Sieverts. To assess the biological effects of radiation, it is mainly used equivalent dose rate radiation, measured in Sieverts per hour. That is, this is an assessment of the impact of radiation on the human body per unit of time, in this case per hour. Considering that 1 Sievert is a significant dose of radiation, for convenience, a multiple of it is used, indicated in micro Sieverts - μSv/hour:

1 Sv/hour = 1000 mSv/hour = 1,000,000 μSv/hour.

Values ​​that characterize the effects of radiation over a longer period, for example, 1 year, can be used.

For example, the radiation safety standards NRB-99/2009 (clauses 3.1.2, 5.2.1, 5.4.4) indicate the norm of permissible radiation exposure for the population from man-made sources 1 mSv/year .

The regulatory documents SP 2.6.1.2612-10 (clause 5.1.2) and SanPiN 2.6.1.2800-10 (clause 4.1.3) indicate acceptable standards for natural sources of radioactive radiation, size 5 mSv/year . The wording used in the documents is "acceptable level", very successful, because it is not valid (that is, safe), namely acceptable .

But in regulatory documents there are contradictions regarding the permissible level of radiation from natural sources. If we sum up all the permissible standards specified in regulatory documents (MU 2.6.1.1088-02, SanPiN 2.6.1.2800-10, SanPiN 2.6.1.2523-09) for each individual natural source of radiation, we obtain that background radiation from all natural sources of radiation (including the rare gas radon) should not exceed 2.346 mSv/year or 0.268 μSv/hour. This is discussed in detail in an article on this site. However, the regulatory documents SP 2.6.1.2612-10 and SanPiN 2.6.1.2800-10 indicate an acceptable standard for natural radiation sources of 5 mSv/year or 0.57 μS/hour.

As you can see, the difference is 2 times. That is, an increasing factor of 2 was applied to the permissible standard value of 0.268 μSv/hour without any justification. This is most likely due to the fact that in the modern world we are massively surrounded by materials (primarily building materials) containing radioactive elements.

Please note that in accordance with regulatory documents, the permissible level of radiation from natural sources radiation 5 mSv/year, and from artificial (man-made) sources of radioactive radiation only 1 mSv/year.

It turns out that when the level of radioactive radiation from artificial sources exceeds 1 mSv/year, negative effects on humans can occur, that is, lead to diseases. At the same time, the standards allow that a person can live without harm to health in areas where the level is 5 times higher than the safe man-made exposure to radiation, which corresponds to the permissible natural background radioactive level of 5 mSv/year.

According to the mechanism of its effect, types of radiation radiation and the degree of its effect on a living organism, natural and man-made sources of radiation they do not differ.

Still, what do these norms say? Let's consider:

• the norm of 5 mSv/year indicates that a person over the course of a year can receive a maximum total dose of radiation absorbed by his body of 5 miles Sievert. This dose does not include all sources of technogenic impact, such as medical ones, from environmental pollution with radioactive waste, radiation leaks at nuclear power plants, etc.
• to estimate what dose of radiation is permissible in the form of background radiation at a given moment, we calculate: the total annual rate of 5000 μSv (5 mSv) is divided by 365 days a year, divided by 24 hours a day, we get 5000/365/24 = 0, 57 µSv/hour
• the resulting value is 0.57 μSv/hour, this is the maximum permissible background radiation from natural sources, which is considered acceptable.
• on average, the radioactive background (it has long ceased to be natural) fluctuates between 0.11 - 0.16 μSv/hour. This is normal background radiation.

We can summarize the permissible radiation levels in force today:

• According to regulatory documentation, the maximum permissible level of radiation (background radiation) from natural radiation sources can be 0.57 μS/hour.
• If we do not take into account the unreasonable increasing coefficient, and also do not take into account the effect of the rarest gas - radon, we obtain that, in accordance with regulatory documentation, normal background radiation from natural radiation sources should not exceed 0.07 µSv/hour
• maximum permissible normative total dose received from all man-made sources, is 1 mSv/year.

We can say with confidence that the normal, safe radiation background is within 0.07 µSv/hour , operated on our planet before the industrial use of radioactive materials, nuclear energy and atomic weapons (nuclear tests) by humans.

And as a result of human activity, we now believe acceptable radiation background is 8 times higher than the natural value.

It is worth considering that before the active exploration of the atom by man, humanity did not know what cancer was in such massive numbers as is happening in the modern world. If cancer cases were registered in the world before 1945, they could be considered isolated cases compared to statistics after 1945.

Think about it , according to WHO (World Health Organization), in 2014 alone, about 10,000,000 people died on our planet from cancer, this is almost 25% of the total number of deaths, that is in fact, every fourth person who dies on our planet is a person who died from cancer.

Also, according to WHO, it is expected that in the next 20 years, the number of new cancer cases will increase by approximately 70% compared to today. That is, cancer will become the leading cause of death. And no matter how carefully, the governments of states with nuclear energy and atomic weapons would not mask the general statistics on the causes of mortality from cancer. We can confidently say that the main cause of cancer is the effect on the human body of radioactive elements and radiation.

For reference:

To convert µR/hour to µSv/hour You can use a simplified translation formula:

1 μR/hour = 0.01 μSv/hour

1 µSv/hour = 100 µR/hour

0.10 µSv/hour = 10 µR/hour

The specified conversion formulas are assumptions, since μR/hour and μSv/hour characterize different quantities, in the first case it is the degree of ionization of the substance, in the second it is the absorbed dose by living tissue. This translation is not correct, but it allows us to at least approximately assess the risk.

Conversion of radiation values

To convert values, enter the desired value in the field and select the original unit of measurement. After entering the value, the remaining values ​​in the table will be calculated automatically.

X-ray examinations in medicine still play a leading role. Sometimes without data it is impossible to confirm or make a correct diagnosis. Every year, techniques and X-ray technology are improved, become more complex, and become safer, but, nevertheless, the harm from radiation remains. Minimizing the negative impact of diagnostic radiation is a priority goal of radiology.

Our task is to understand, at a level accessible to anyone, the existing figures of radiation doses, their units of measurement and accuracy. We will also touch upon the reality of possible health problems that this type of medical diagnosis can cause.

What is X-ray radiation

X-rays are a stream of electromagnetic waves with wavelengths in the range between ultraviolet and gamma radiation. Each type of wave has its own specific effect on the human body.

At its core, X-ray radiation is ionizing. It has high penetrating ability. Its energy poses a danger to humans. The higher the dose received, the higher the harmfulness of radiation.

About the dangers of exposure to X-ray radiation on the human body

Passing through the tissues of the human body, X-rays ionize them, changing the structure of molecules, atoms, in simple terms - “charging” them. The consequences of the resulting radiation can manifest themselves in the form of diseases in the person himself (somatic complications), or in his offspring (genetic diseases).

Each organ and tissue is affected differently by radiation. Therefore, radiation risk coefficients have been created, which can be seen in the picture. The higher the coefficient value, the higher the tissue’s susceptibility to the effects of radiation, and hence the risk of complications.

The hematopoietic organs most susceptible to radiation are the red bone marrow.

The most common complication that appears in response to radiation is blood pathologies.

A person experiences:

• reversible changes in blood composition after minor amounts of radiation;
• leukemia – a decrease in the number of leukocytes and a change in their structure, leading to disruptions in the body’s functioning, its vulnerability, and decreased immunity;
• thrombocytopenia – a decrease in the content of platelets, blood cells responsible for clotting. This pathological process can cause bleeding. The condition is aggravated by damage to the walls of blood vessels;
• hemolytic irreversible changes in the composition of the blood (decomposition of red blood cells and hemoglobin) as a result of exposure to powerful doses of radiation;
• erythrocytopenia - a decrease in the content of erythrocytes (red blood cells), causing the process of hypoxia (oxygen starvation) in the tissues.

FriendnopathologistsAnd:

• development of malignant diseases;
• premature aging;
• damage to the lens of the eye with the development of cataracts.

Important: X-ray radiation becomes dangerous in case of intensity and duration of exposure. Medical equipment uses low-energy radiation of short duration, so it is considered relatively harmless when used, even if the examination has to be repeated many times.

A single exposure to radiation that a patient receives during conventional radiography increases the risk of developing a malignant process in the future by approximately 0.001%.

note: unlike exposure to radioactive substances, the harmful effects of rays stop immediately after turning off the device.

The rays cannot accumulate and form radioactive substances, which will then become independent sources of radiation. Therefore, after an x-ray, no measures should be taken to “remove” radiation from the body.

In what units are the doses of received radiation measured?

It is difficult for a person far from medicine and radiology to understand the abundance of specific terminology, dose numbers and units in which they are measured. Let's try to bring the information to an understandable minimum.

So how is X-ray dose measured? There are many units of measurement for radiation. We won't go into everything in detail. Becquerel, curie, rad, gray, rem - this is a list of the main quantities of radiation. They are used in various measurement systems and areas of radiology. Let us dwell only on those that are practically significant in x-ray diagnostics.

We will be more interested in X-rays and sieverts.

The level of penetrating radiation emitted by an X-ray machine is measured in a unit called “roentgen” (P).

To assess the effect of radiation on humans, the concept was introduced equivalent absorbed dose (EDD). In addition to EPD, there are other types of doses - all of them are presented in the table.

The equivalent absorbed dose (in the picture - Effective equivalent dose) is a quantitative amount of energy that the body absorbs, but it takes into account the biological response of body tissues to radiation. It is measured in sieverts (Sv).

A sievert is approximately comparable to the value of 100 roentgens.

The natural background radiation and doses delivered by medical X-ray equipment are much lower than these values, so they are measured using the values ​​of a thousandth (milli) or one millionth (micro) of Sievert and Roentgen.

In numbers it looks like this:

• 1 sievert (Sv) = 1000 millisievert (mSv) = 1,000,000 microsievert (µSv)
• 1 roentgen (R) = 1000 milliroentgen (mR) = 1,000,000 milliroentgen (µR)

To estimate the quantitative part of the radiation received per unit of time (hour, minute, second), the concept is used - dose rate, measured in Sv/h (sievert-hour), μSv/h (microsievert-hour), R/h (roentgen-hour), μR/h (micro-roentgen-hour). Likewise - in minutes and seconds.

It can be even simpler:

• total radiation is measured in roentgens;
• the dose received by a person is in sieverts.

Radiation doses received in sieverts accumulate over a lifetime. Now let's try to find out how many sieverts a person receives.

Natural radiation background

The level of natural radiation is different everywhere, it depends on the following factors:

• altitude above sea level (the higher, the harder the background);
• geological structure of the area (soil, water, rocks);
• external reasons - the material of the building, the presence of nearby enterprises that provide additional radiation exposure.

Note:The most acceptable background is considered to be one in which the radiation level does not exceed 0.2 μSv/h (microsievert-hour), or 20 μR/h (micro-roentgen-hour)

The upper limit of the norm is considered to be up to 0.5 μSv/h = 50 μR/h.

Over several hours of exposure, a dose of up to 10 μSv/h = 1 mR/h is allowed.

All types of X-ray examinations fit into safe standards for radiation exposure, measured in mSv (millisieverts).

Permissible radiation doses for humans accumulated over a lifetime should not exceed the limits of 100-700 mSv. Actual exposure values ​​for people living at high altitudes may be higher.

On average, a person receives a dose of 2-3 mSv per year.

It is summed up from the following components:

• solar and cosmic radiation radiation: 0.3 mSv – 0.9 mSv;
• soil-landscape background: 0.25 – 0.6 mSv;
• radiation from housing materials and buildings: 0.3 mSv and above;
• air: 0.2 – 2 mSv;
• food: from 0.02 mSv;
• water: from 0.01 – 0.1 mSv:

In addition to the external dose of radiation received, the human body also accumulates its own deposits of radionuclide compounds. They also represent a source of ionizing radiation. For example, in bones this level can reach values ​​from 0.1 to 0.5 mSv.

In addition, there is irradiation with potassium-40, which accumulates in the body. And this value reaches 0.1 – 0.2 mSv.

note: To measure background radiation, you can use a conventional dosimeter, for example RADEKS RD1706, which gives readings in sieverts.

Forced diagnostic doses of X-ray irradiation

The amount of equivalent absorbed dose for each x-ray examination may vary significantly depending on the type of examination. The radiation dose also depends on the year of manufacture of the medical equipment and the workload on it.

Important: modern X-ray equipment produces radiation tens of times lower than the previous one. We can say this: the latest digital X-ray technology is safe for humans.

But we will still try to give average figures for the doses that a patient can receive. Let us pay attention to the difference between the data produced by digital and conventional X-ray equipment:

• digital fluorography: 0.03-0.06 mSv (the most modern digital devices produce radiation in a dose of 0.002 mSv, which is 10 times lower than their predecessors);
• film fluorography: 0.15-0.25 mSv, (old fluorographs: 0.6-0.8 mSv);
• X-ray of the chest organs: 0.15-0.4 mSv;
• dental (dental) digital radiography: 0.015-0.03 mSv., conventional: 0.1-0.3 mSv.

In all of these cases we are talking about one picture. Studies in additional projections increase the dose in proportion to the frequency of their conduct.

The fluoroscopic method (involves not photographing an area of ​​the body, but a visual examination by a radiologist on a monitor screen) produces significantly less radiation per unit of time, but the total dose may be higher due to the duration of the procedure. Thus, during 15 minutes of chest X-ray, the total dose of radiation received can be from 2 to 3.5 mSv.

Diagnosis of the gastrointestinal tract – from 2 to 6 mSv.

Computed tomography applies doses ranging from 1-2 mSv to 6-11 mSv, depending on the organs being examined. The more modern the X-ray machine is, the lower the doses it gives.

We especially note radionuclide diagnostic methods. One radiotracer-based procedure produces a total dose of 2 to 5 mSv.

A comparison of the effective doses of radiation received during the most commonly used diagnostic tests in medicine and the doses received daily by humans from the environment is presented in the table.

Important:Magnetic resonance imaging does not use x-rays. In this type of study, an electromagnetic pulse is sent to the diagnosed area, exciting the hydrogen atoms of the tissues, then the response that causes them is measured in the generated magnetic field with a high intensity level.Some people mistakenly classify this method as X-ray.