21

I.

History of radiology. Radioactivity and dose. Dosimetry: the units of radioactivity and methods of measuring a |definition|dose of radiation exposure. The structure|building| of radiometers and dosimeters. NURS-97, IRR-99

Radiology |beam|is the section|division| of medicine, which|what| works out the theory and practice of using ionizing radiation for diagnostic (radiodiagnosis) and treatment (radiotherapy).

Radiodiagnosis studies|learns| the use of radiations for the evalvulation of different organs and systems structure|building| and functions. Radio diagnosis includes:|switches| thermography|, X-ray diagnosis|, radionuclide diagnostics| (РND|), ultrasound diagnosis (US), computer-tomography diagnosis (CТ|), and magnetic-resonance imaging (MRI|) intervention radiology.

Radiotherapy studies|learns| the use of ionizing radiation for the treatment of oncologic and unoncologic diseases.

At the end of|at close of| the 20^th century all the methods of diagnosis and treatment, wich are based on the use of ionizing radiations, ultrasound, infra-red radiation, magnetic fields of atomic nuclei, were united|combines| into a single scientific speciality — radiology.

The history of medical radiology

The x-ray discovery must be considered as one of the fastest known discoveries in the world. Wilhelm Conrad Roentgen (1845-1923), a German physicist was the professor of physics at Wurzburg (Munich) University. He began his experiments on x-rays in the late October of 1895 which ultimately yielded the actual experi­mental discovery on the 8^th of November, 1895. However, he announced about it in press on the 28th of December, 1895. The discovery was made known to the world on the 5th of January, 1896. Clinically, the first medical radiograph was produced in Great Britain by AA Campbell Swinton and JC Stanton on the 13^th of January, 1896. Although the prospects for the x-ray diagnosis were immediately recognized, Roentgen refused to enter any commercial contract to exploit his discovery. He was of the opinion that his discovery belonged to the humanity, and should not be the subject of patents, licenses and contracts. He was awarded the first Nobel Prize for physics in 1901.

In 1896 Anry Bekkerel, a French scientist discovered natural radioactivity (the second notable event).

Radioactivity is decay of unstable nuclei, giving off radiation until they become stable, for example:

The materials which|what| emit ionizing radiation are named|called| radioactive materials.

In 1896 Marie and Pierre Curie isolated polonium| and radium out of uranium ore.

In І934 Irene and Jule| Curie discovered artificial radionuclides (radionuclides or isotopes) - the varieties of elements with the identical protons number in the nuclear but different neutrons amount|quantity|, thus having the same order number in Mendeleev table |, but different|diverse| mass figures. Artificial radionuclides (radionuclides) are received |receives| in nuclear reactors while bombarding stable chemical elements by neutrons or elementary particles|lobules,cloves,sections| in accelerators of elementary particles|lobules,cloves,sections|. The nuclei of radionuclides | dicay with the emission of ionizing radiation, for example:

Radioactivity determined by the natural radionuclides is named|called| natural, while|but| the radioactivity determined by artificial radionuclides is named|called| artificial.

In 1940 Flerov and Petrgak К.О. discovered the phenomenon of the independent decomposition of the uranium nuclei into large fragments, which is accompanied by the freeing of two-three neutrons able to cause|calls| the subsequent|consequent| division of other uranium nuclei. This discovery|discovery| became the basis|foundation| for realization of the chain reeffect. In 1942 Enrico| Fermi in Chicago|/USA/ first built an operating atomic reactor. In the process of the work of the reactor they got|receives| the raw material, for making a-bombs, and in 1945, first in history, the energy of atomic nucleus was used to the humanity harm - a-bombs were thrown on the Japanese cities|towns| Hiroshima and Nagasaki by American pilots|military|, which caused the death of more than|more than| 300 thousand people.

The using of the atomic weapon|arm| became a shove|push| to the|by| stormy|rough| development of radiobiology — the science which|what| studies|learns|of biological effects. A radiobiology includes|switches|: radiation hygiene, radiation biochemistry, radiation genetics, radiation cytology, radiation immunology, and radiation ecology, and space radiobiology, radiobiology of tumours|swelling|, prophylaxis and treatment of radiodefects.

The structure|building| of the atom. The atomic nucleus consists of protons, neutrons and other elementary particles|parts,stakes,portions,shares| which are kept|retained,maintained,deducted| together due to the nuclear attreffect. The protons and neutrons sum|amount| makes|folds| the mass number of chemical elements. Around|about| the nucleus negatively charged electrons rotate|turned,wrapped,applied|. The number of the protons in the nuclear equals to its |its| number in Mendeleev periodic system.

The atomic nuclei of heavy elements are unsteady and beginning with the 84th element turn into other nuclides.

The types of radioactive interaction|conversions|

1. The alpha-decay |- is the emission of alpha-particles ( ) out of nuclei of natural radioactive elements:

2. The electronic nuclear beta-decay - | is the emission of beta-particles (electron, ) out of natural or artificial radioactive elements:

3. The positron | nuclear beta-decay is the emission of beta-particles (positron, ) out of natural or artificial radioactive elements:

4. The K-capture|capture,rapture,seizure| (orbital electron capture) a nuclear proton captures |delights,enthrals,enraptures| an electron from the K-layer (the nearest level|next| to|by| the nuclear one) and turns into a neutron. The order number of the element diminishes by one. The electron from another layer passes to the freed |turns| place in the K-layer which is accompanied by the emitting of the characteristic radiation quantum:

5. The spontaneous decay of nuclei is observed|exists| in the radioactive elements with the greate atomic number (²³⁵U, ²³⁹Pu etc.) if their nuclei are captured by slow neutrons:

The nuclear decay is accompanied by the emission of nuclear energy. Neutrons (which emerge at the decay of nuclei) cause|calls| the decay of other nuclei (nuclear chain reeffects).|stands|

6. Thermonuclear reeffects (synthesis of nuclei) emerge if the teADLratures achieve several|a little| millions degrees. At this rate the nuclei of light|light| elements are united into the nuclei o heavier|difficult| elements:

The law of the radioactive decay permanency: in the regular intervals of time there occurs the nuclear transformation|conversion| of equal parts (portions)|portions| of active radionuclides atoms:

N_t=N₀ e-lt

Where N₀ is the amount|quantity| of active atoms in the initial|elementary| moment (t=0); N_t is the amount|quantity| of the radioactive atoms which remained in|from,because of| the time of t; e - is the permanent|constant| of the decay, which is determined by the part|part,stake,portion,share| of the atoms, which dicay per a|after| time unit.

The part|part,stake,portion,share| of the atomic nuclei, which decay, is a constant for every radionuclide| and named|called| |constant| the decay constant (λ):

,

where T (half-decay period) is theduring which|what| the half of active atomic nuclei of this radionuclides dicay. Radionuclides with the period of half-decay more than 15 days are considered to be long-living radionuclides, less than 15 days — short-living radionuclides |.

The radioactive substance activity is a number of nuclear interaction|conversions| per|after| a time unit.The unit of activity is becquerel | (Bq |) - one transformation|conversion| per second; МBq=10⁶ Bq|, GBq=10⁹ Bq|, ТBq=10¹² Bq|). The

systemless| unit of activity is curie (Cu|). 1 Cu| = 3,71010Bq, derivatives of|marching| Cu|: milicurie | (mCu|) = 3,7·107Bq; microcurie (mcCu|) = 3,7·104Bq.

Ionizing radiation is the radiation which|what| at interacting with the material causes the|to| excitation of the material atoms and molecules and leads to the emerging of oppositely charged ions.

Types of ionizing radiations:

• corpuscular: alpha-radiation, beta-rays, proton radiation, and neutron radiation;

• quantum or photonic: gamma-radiation (electromagnetic radiation that arises up during the transformation|conversion| of radioactive nuclei or during the intereffect of the fast|quick,fast| charged particles with the material), x-ray (brake radiation) and space radiation.

The properties|virtues| of ionizing radiations:

1) The penetrating property - is the ability|virtue| of the ionizing radiation to penetrate through different|diverse| materials|fabrics| (inversely proportional to the material density|Wednesday|);

2) The ionizing property —is the ability|virtue| of the ionizing radiation to split molecules into positively and negatively charged ions, for example: H₂O = H⁺ + OH-;

3) The photochemical property — is the ability|virtue| of the ionizings radiation|virtue| to cause photolysis AgBr = Ag⁺ + Br ^- (used while luminescenting photographic materials|fabrics|);

4) The luminescent (scintillation) property — is the ability|virtue| of the ionizings radiation|virtue| to cause scintillation |s (luminescence) of some|certain| chemical materials;

5) The biological property — is the ability|virtue| of the ionizings radiation|virtue| to cause|virtue| functional, anatomic and metabolic changes|changing| at the others levels of the biological organization (molecular, subcellular, cellular, organs systems level and organismic level);

6) The cumulative property—is the ability|virtue| of the ionizings radiation|virtue| to accumulate|virtue| negative effects of radiation exposures in the organism, which eventually can cause|calls| undesirable remote|distant| consequences(malignant tumours|swelling|, congenital malformations, genes mutations, life-span reduction |abbreviations,shortening| );

7) The thermal property - is the ability|virtue| of the ionizings radiation|virtue| to be accompanied by thermal energy emission.

Radioactive radiations are not perceived by sense organs, they are invisible, do not have either smells or taste|relish|, that is why|that is why| at the moment of radiation exposure the organism does not feel its effect|act|.

The Material- ionizing radiation intereffect

The primary mechanisms of the material- ionizing radiation intereffect are the excitation of the atom or its |its| ionization |appears| as a result of|because of,owing to| transferring of the radiation energy to the atomic electron.

Depending on the magnitude|value| of linear energy transmission (LET|) all ionizing radiations are divided into rarely|seldom| - and densely- ionizing radiations |. To the Rarely-ionizing radiations belong the radiations with LET | less than 10 кеV/mкm — β-| and quantum radiations. The densely- ionizing radiation has LET | more than 10 кеV/mкm - neutrons, protons, nuclei of heavy|difficult| chemical elements.

Different|diverse| types of radiations cause|calls| different types of ionization.

The primarily-ionizing | radiations transfer their ionization to the medium directly by |Wednesday| charged particles|lobules,cloves,sections| (α-|, β-|particles, protons, heavy|difficult| ions, π-mesons.

The quantum radiations (x-ray photography and γ-radiation) and the neutrons radiation belong|behaves| to the|by| secondary-ionizing radiations|.

The material- ionizing quantum radiation intereffect

At the material- ionizing quantum radiation intereffect arise up the following effects:

1. The photoelectric|photovoltaic| effect (photoeffect) comes as a result of|because of,owing to| transmission of the whole quantum energy to the orbital electron (the energy of quantum is 0,1 - 0,3 МеV)|.

2. The Compton effect (Compton | dispersion) consists in the transmission of part|portion| of the γ-quantum energy to the electron|Wednesday| and changing|changing| of its initial direction (the energy of quantum is 0,1 - 0,3 МеV)|.

3. Formation of electrons-positrons pairs|couples| arises up as a result of collision of a photon with the nucleus (the photon energy is more than 1 МeV|).

The material - ionizing corpuscular radiation intereffect

At the|particles| intereffect of α-particles with the material there arises up the excitation and ionization of atoms as a result of|because of,owing to| inelastic collisions with orbital electrons. If α-particles|particles| strike the atomic nucleus there arises up the nuclear reeffect with the emission of particles (neutrons, α-particles|particles| and others).

The β-particles intereffect with the material leads to ionization, the excitation of atomic nuclei and braking radiation (as a result of|because of,owing to| inelastic and elastic collisions with orbital electrons).

Breag`s curve|. The charged particles penetrate more deeply into materials which increase the number of |quantity| intereffects|increases| with atoms and molecules. The speed of particles diminishes - consequently, the probability of new intereffects rises up - and the frequency of ionizations increases.

With the augmentation of a run, the particle ionization increases in the substance and culminates (Breag`s peak), and then quickly decreases up to zero.

The material - neutrons intereffect.

The material - neutrons intereffect depends on the neutron energy.

1. Slow neutrons:a|but|) ultracold — 10 ^-7 eV|; b) cold — to 5 •10 ^-3 eV|; c) thermal — to 0,5 eV|; d) super-thermal — to 10 eV|.

2. Resonance neutrons — 0,5 кeV|.

3. Intermediate neutrons — 0,2 МeV|.

4. Fast neutrons — to 20 МeV|.

5. Very fast|quick,fast| neutrons - to 300 МeV|.

6. Ultrafast (relativistic) neutrons — over|more than| 300 МeV|.

Slow neutrons are captured by nuclei|Wednesday|, as a result there can be the induced radioactivity, for example:

Resonances neutrons are captured |enthralled| only by heavy|difficult| nuclei. For intermediate and fast|quick,fast| neutrons the elastic collisions and nuclear reeffects are|appears| typical|model|.

For fast|quick,fast| neutronsboth inelastic and elastic collisions are characteristic|character,typical|. As a, result protons, α-particles|particles|, neuteron and other particles capable of ionising are irradiated (indirect ionization by neutrons).

DOSIMETRY OF IONISING RADIATION EXPOSURE

Dosimetry is the quantification and evaluation |definition| |quantity|of ionizing radiations.

The tasks of clinical dosimetry:

1) revealing |discovery| the radiation sources |spring,source|, identification of the radiation types |appearance|, activity and energy;

2) determining the radiation influence degree on the object being irradiated.

The dose of ionizing radiations is|calls| the energy transferred from radiation to the elementary volume or mass of the material being exposed.

The exposure radiation dose (photonic: x-ray photography and gamma-radiations - ERD)- this is a quantitative characteristic of radiation based on its ability|power| to ionize the air. As a |after| unit of the exposure radiation dose in the SI system there is accepted such a dose , which|what| in 1 kg of dry air generates the ions with the charge of 1 Coulomb(Cl, ampere-second) | (every sign)— Cl/кg. The out-systemic| unit of the exposure radiation dose is a Roentgen (R). At radiating with the expouse radiation dose equal to 1R in 1 sm³ of dry air under normal physical conditions there are formed 2,08·10⁹ pairs|couples| of ions. The derivative of|marching| Roentgen: 0,001R=1 mR|; 0,000001 Р = 1mкR.

The exposure radiation dose power|capacity| of photonic radiation (Р_ERD|) is the exposure radiation dose per a time unit —1 Cl/кg·sec =1 А/кg. An out-system unit — R/hour, mR/sec|yes|.

The absorbed ionizing radiation dose (RAD) is the energy transferred from radiation to a mass unit of the material being exposed. In the SI system Grey | (Gy|) is |appears| 1 Joule /кg. An out-system unit of the absorbed dose is rad (from „ radiation adsorbed dose”).

1 Gy| = 100 rad, 1 rad = 0,01 Gy|.

The power|capacity| of the absorbed ionizing radiation dose (P_RAD) is RAD per a time unit (Gy/sec, rad/sec).

The integral absorbed radiation dose is the average energy transferred to a certain|definite| mass of the exposed tissues, organ, part|portion| or the whole body, - Gy·kg (rad·kg).

The equivalent radiation dose (Н) — Sivert |¹ (Sv|) is such absorbed ionizing radiation dose(of any|some| type), which|what| causes the same biological effect as 1 Gy| of the absorbed ionizing radiation dose of x-ray or gamma-radiations (Joule /kg); 0.01 Sv=1 ber( the biological equivalent of roentgen).

The personal effective radiation exposure dose is the sum|amount| of equivalent radiation doses which the|what| human absorbs during|receives| the life-time.

The collective effective radiation exposure dose is equal to the personal effective radiation accumulated doses of the public group for a|after| definite time|definite| interval|space|.A measurement unit — person - Sivert | (person-Sv).

The public dose is equal to all the effective radiation accumulated doses of the country public from all the sources|springs| of radiation exposure. A measurement unit – Sivert (Sv) |.

The equivalent radiation dose (НТ|) in an organ or tissue of Т is the magnitude which is defined as a result of montiplication of the absorbed dose D in a separate organ or tissue T in the radiation suspended factor of WR.

НT = ДТ| • WR

The radiation suspended factor is the coefficient|ratio| which|what| takes into account the biological efficiency of different|diverse| types of ionizing radiations in the association with the different|diverse| magnitude|value| of the linear transmission of energy (LTE|). LTЕ| is the ratio of the complete energy of dЕ which is passed to the material by the charged particle as a result of|because of,owing to| collisions on the way of dL, and the|by| length of this way.

The value|importance,meaning| of the radiation suspended| factors (SR) (see|q.v.| table|. 1.1.).

_{Table 1.1. The Value|importance,meaning| of the radiation suspended factors (SR)}

Types of radiation		WR
Photons-x-rays and G-rays, all energies	1
B-ray|, muons, all energies		1
Protons (<10 МeV|)		10
Neutrons (2 – 10 МeV|)	10
Alpha –rays, heavy|difficult| nuclei of return	20

The distribution of doses in separate organs and tissues depends on the magnitudes|values| of equivalent doses and the value|importance,meaning| of the tissues suspended | factors for separate tissues or organs.

The tissue | suspended factor (Wt) is the coefficient|ratio| which|what| reflects the relative stochastic (probable|probable|) risk of irradiating a separate tissue or organ| to|by| the total|common| risk at the uneven radiation exposure of the body (see|q.v.| tabl|. 1.2.)

Table 1.2. The value|importance,meaning| of the tissues suspended | factors

№	Tissue or organ	Wt	№	Tissue or organ	Wt
1	Gonades	0,20	8	Liver	0,05
2	Marrow(red)	0,12	9	Esophagus	0,05
3	Colon	0,12	10	Thyroid	0,05
4	Lungs	0,12	11	Skin	0,01
5	Stomach	0,12	12	A bone surface	0,01
6	Urinary bladder		13	Other organs	0,05
7	Mammary|suckling| gland	0,05	14

The effective dose of radiation exposure (Е) is the sum|amount| of the equivalent doses of works (НТ|) in separate organs and tissues on the corresponding tissues suspended| factors (Wt). A unit of measuring is Sivert| (Sv|).

.

The effective dose allows defining the probable|probable| total risk from the radiation exposure of different|diverse| areas of the body in different absorbed |diverse| doses. The value|importance,meaning| of effective doses is summed up for each person during the life-time and this total magnitude|value| is adopted as the index of the accumulated risk of radiation exposure.

The collective effective dose (S) is the sum|amount| of personal effective doses of the radiation exposure of a certain|definite| group of public for|after| a certain|definite| interval|space| of time or the sum|amount| of average group | effective doses works on the number of persons|personalities,individuals| in the corresponding groups, which form the collective for which|what| it is |it|calculated. A measuring unit — person-Sivert| (people-Sv).

The public| dose is the total effective dose of irradiating a country public from all sources|springs| of radiation exposure. A measuring unit – Sivert (Sv|).

The power|capacity| of the radiation exposure effective dose is the effective dose per a time unit – 1SV\s; 0.01 Sv\s=1 Ber\s.

The effective period of half-decay and half-excretion of a radionuclide| (Т1/2|) is the time during|for| which|what| the amount|quantity| of radio nuclides| in the organism diminishes twice|double| as a result of|because of,owing to| its|its| radioactive disintegration and biological excretion|conclusion,deducing,inference,withdrawal|.

Methods of Dosimetry

Distinguish the physical, chemical and biological methods of dosimetry: ionization, luminescent, semiconductive, thermoluminiscent, neutron-activating, calorimetrical, photographic, chemical, biological and calculative|computation| (mathematical).

The ionization method of dosimetry is used with|by means of| an ionization chamber|cell| and based on estimating|appraisal| the environment ionization |Wednesday| degree through|from,because of| which|what| the radiation passes. Than greater power|capacity| of dose, the more so|nevertheless| arises up ions, the greater ionization current. Measuring the size|value| of ionization current get|receives| the picture of power|capacity| of dose of ionizing radiation. Scheme of structure|building| and principle the robots of ionization dosimeter are resulted|pointed| on fig|.1.1.

Fig.1.1 The structure scheme and principle of the ionization dosimeter work.

П1 и П2 — electrodes|; Б —battery; И-| radiation; O window| in an ionization chamber|cell|; Г galvanometer.

The scintillation method of dosimetry consists in measurings the intensity of the light|photic| flashes, which arise up in the materials with a luminescent property (potassium iodide, sodium, caesium or anthracene, stilbene | and others) during passing of x-rays or γ-rays through|from,because of| them. The structure|building| scheme of a luminescent dosimeter see |q.v.|fig|.1.2

Fig|. 1.2 The luminescent dosimeter structure scheme.

The semiconductive method of dosimetry – during radiation exposure in semiconductive detectors there arises up the current, after the magnitude|value| of which|what| it is possible to define the radiation dose power|capacity|, which effects on the detector.

The thermoscintilation (photoscintilation|, radioscintilation|) method is based on the ability|power| of crystalline люмінофорів| (lithium fluorid| activated by silver) to accumulate the absorbed radiation energy. In case of additional heating of crystals in a certain|definite| mode|regime| there occurs the thermoscintilation| "flash", the intensity of which|what| depends on the dose of radiation exposure, which люмінофор| has absorbed.

The neutron-activating method is the determination|definition| of the directed|pointed| radioactivity as a result of|because of,owing to| neutrons streams influence.

The photographic method of dosimetry is based on the ability|power| of radiation to cause the|calls| photolysis of haloid silver (see above), as a result of which there occurs its |its| partial recreation|reproduction,reproducing|. In the process of revealing in the places|seats| of radiation exposure the film darkens proportionally to the dose of radiation exposure.

The chemical method — is based on the ability|power| of ionizing radiations to cause|calls| in the compounds the dissociation of polyatomic molecules with the formation of new compounds. The transparency or colour of solutions changes, some part of the dissociation product sediments or turns into gas. The quantitative estimation|appraisal| of these changes|changing| allows defining the dose of radiation exposure, using the measuring system graduated| with applying of the standard radiant|spring,source|.

The calorimetrical (thermal) method of dosimetry — is based on measuring the amount|quantity| of heat, which is excreted in a detector at absorbing ionizing radiations (little used in medicine because of its|its| low sensitiveness).

The calculation|computation| (mathematical) method —supposes using tables and nomograms| for the calculating|computation| the personal absorbed doses at different|diverse| variants of irradiating a man.

The biological methods of dosimetry are based on evalvulationing biomaterials (the chromosomal analysis of lymphocytes | of the peripheral blood, the| marrow biopsy phantom, the electronic paramagnetic resonance of the teeth enamel extracted after medical indications|demonstrations|) and the account of radio reeffects of the organism. This method of dosimetry is used in clinical practice.

Types of devices for measuring of dose and radioactivity

Dosimeters| are personal, searching| dosimeters of the defense|protection| control, laboratory and clinical (VJ – 18, VJ - 23). They are used for the determining|definition| of doses power|capacity|.

Fig|.1.3 The radiometer concept block scheme|building|.

Radiometers are used for the determination|definition| of a sample activity|model|, that of the external environment objects |Wednesday| and levels of radioactive contamination of surfaces and in vitro diagnosis.

There are laboratory radiometers | for the determination|definition| of activity of the ¹³⁷Cs and ⁴⁰K, |definition| of ²²⁶Ra and ²³²Th; wells radiometers, spectrometers, meters of a man radiation (or spectrometers), — SRM| (spectrometer of the radiation of a man), SRB| (spectrometer of the radiation of the whole body) and clinical radiometers (radiometers, radiographs, scanners, scintillation gamma-chambers,|cells| single-photon emission computer tomography – SPECT|, positron emission tomography - PET).

The norms|standards| of the Ukraine radiation safety

(NURS| – 97, NURS| – 97/D-2000)

These are the basic|main| state documents|papers| which set|establishes| the hygienical|sanitary| norms|standards| of the radiological| defense|protection| of people.

The radiological defence of the public is based on the following principles of the radiation safety:

• The principle of justified - the practical activity which|what| is accompanied by irradiating people, must not be carried out, if the benefit|profit| from it |it| does not exceed the harm which|what| it |it| inflicts|drifts| to the man or society;

• The non-exceeding principle - the levels of the radiation exposure cumulative effective doses as a result of|because of,owing to| the industrial activity must not exceed the established limits|quotas| of doses (see|q.v.| table.1.3.);

• The principle of optimization - personal doses and the amount|quantity| of the persons|personalities,individuals| exposed to the rays must be so minimal, as it can be achieved taking into account social and economic|economical| factors.

By the NURS| -97there have been set the following categories of the persons|personalities,individuals| |what| exposed to |feels| radiation exposure:

1. Category A|but| (personnel) are the persons|personalities,individuals| which work |what| directly|immediately| with sources of |springs,sources| ionizing radiations;

2. Category B (personnel) are the persons|personalities,individuals| which do not work |what| directly|immediately| with sources of |springs,sources| ionizing radiations|springs,sour, but in accordance| to the location|disposition| of there workplaces|jobs| in the premises with radiation-nuclear technologies can get|receives| the additional radiation exposure;

3. Category C is the entire public of the country.

Table 1.3. Limits|quotas| of radiation exposure doses (mSv/year)

Limits|quotas| of doses	Category of the persons|personalities,individuals| exposed|what|ex to radiation exposure
	A	B|	|C
LDЕ| (limit|quota| of an effective dose)
Limits|quotas| of the equivalent dose of the external radiation exposure	20	2	1
LD lens (for the lens of an eye)	150	15	15
LD skin ( for the skin)	500	50	50
LD extrim (for hands and feet)	500	50	-

Note: a|but|) the distribution|distributing| of the radiation dose during|for| a calendar year is not regulated

б) the proper limitations function|acts| for the women|wives| of the childbearing age (under 45 years) and expectant mothers|wives|

NURS| - 97 include|switches| 4 groups of the radiation-hygienic|sanitary| regulated magnitudes|values|.

The first group of regulations is set for the control over the practical activity with the purpose of the limitation of the professional radiation exposure in the conditions of normal exploitation of industrial sources of |springs,sources| ionizing radiations. These are the limits|quotas| of doses, derivative|marching| levels, acceptable levels (AL|) and control levels.

The numerical values|importances,meaning| of the doses limits|quotas| (|qtabl|. 1.4.) are set at the levels which|what| exclude the |dismisses,removes| possibility of the emerging of Determinists effects of radiation exposure from the influence of the sum|amount| of the effective doses of all sources|springs,sources|.

The second group of regulations is set with the purpose of the limitation of medical radiation exposure of a man in the medical practice. This group includes the recommended maximum levels|to|. During conductiong roentgen-| and radionuclear investigations they distinguish the following category of patients.

Category of AD|: patients with oncological diseases or with the suspicion for them; patients, the evalvulation of which|what| is conducted with the purpose of differential diagnosis of innate|nee| cardio-vascular| pathology, including vascular peripheral malformations|; patients for whom|what| intervention measures are taken|steps|; persons|personalities,individuals| being explored in the emergency practice | (including traumas) after vital indications|demonstrations|. The maximum radiation exposure dose possible (ADL|) is 100 мSv/year.

Category of BD: patients, for whom evalvulationes are conducted after clinical indicators|demonstrations| at somatic (non-oncologic) diseases with the purpose of clarificating the diagnosis and (or) the choice of the treatment tactic. ADL| - 20 мSv/year.

Category of CD|: persons|personalities,individuals| from the risk groups, who|what| work at enterprises with harmful pathogenic factors and those, who|what| are admitted to work at those enterprises and who|what| pass a professional selection; patients taken off from the medical account, after radical treatment for oncologic diseases at periodic examinations. ADL| - 2 мSv/year.

Category of DD|: persons|personalities,individuals| for whom all types of prophylactic inspection are conducted, except for|unless,with the exception of| those belonging to|by| the category of CD |; persons|personalities,individuals| for whom examinations after medical programs are conducted. ADL| - 1 мSv/year.

The third groupare regulations concerning the dose of radiation exposure of public prevented as a result of|because of,owing to| interference|intervention| in the conditions of a radiation catastrophe. This group includes|equal| interference levels|interventions| and |equal| effect levels|acts||to|.

The fourth group are regulations concerning the dose (prevented as a result of|because of,owing to| interference|intervention|) of radiation exposure of public from the technogenic | strengthened sources|springs| of the natural origin (sources|springs| of the natural origin ionizing radiation, which|what| as a result of economic and production activity of a man were concentrated or their availability was increased ,which led to the formation of the radiation exposure additional to|by| the natural radiation background) This group includes|equal| interference levels|interventions| and |equal| effect levels|acts||to|.

ADL| in emergent situations

When emergent works are carried out for the rescue of people life, the radiation exposure doses of the emergency personnel must not exceed the values|importances,meaning| regulated by NRSU-97|: the equivalent dose of any|some| organ (together with the even radiation exposure of the whole body) must not exceed 500 mSv|. The planned increase|rise| of the personnel radiation exposure doses over|more than| 100 mSv| is accepted with the permission of the Ukrainian Ministry of Health – one time during|for| all the labor activity.

In the Europe and other countries of the world there are Ionizing Radiation Regulation (IRR) are used (see table 1.4).

Table 1.4 Annual doses limits in the Ionizing Radiations Regulations 1999 (IRR 1999)

Limits of doses	smaller 18 years	over 18 years	others
Dose limits for the whole body| ( mSv)	20	6	1
Dose limits|quotas| for the individual organs and tissues( mSv)	500	150	50
Dose limits for the lens of the eye (mSv)	150	15	15