Order writing a unique work
" xml:lang="en-EN" lang="en-EN">Topic: Methods for determining the radioactivity of drugs
" xml:lang="en-EN" lang="en-EN">Questions:" xml:lang="en-EN" lang="en-EN">1. Absolute method for measuring radioactivity
2. Calculation method for measuring radioactivity
" xml:lang="en-EN" lang="en-EN"> 3. Relative method for measuring radioactivity
" xml:lang="en-EN" lang="en-EN">Absolute method for measuring radioactivity
The absolute method is used in the absence of the necessary reference sources for measuring preparations by the relative method or in the case of unknown isotopic composition of radionuclides contained in the test sample.
In the radiometry of drugs, the absolute method uses installations that make it possible to register all beta particles formed during the decay of radionuclides, or a precisely determined part of them. Such devices include installations with end or 4 -counters (for example, radiometer 2154-1M "Protoka", UMF-3, etc.). The measured drug is placed inside the meter and surrounded on all sides by the working volume of gas. Thanks to this, almost all beta particles escaping from the preparation are captured and recorded, i.e., almost 100% counting efficiency is achieved. Thus, when working with such a counter, corrections for absorption and scattering in the preparation and substrate are minimized. But detectors of this type are more complex than gas-discharge counters.
" xml:lang="en-EN" lang="en-EN">To determine absolute activity on installations with 4;font-family:"Symbol"" xml:lang="en-EN" lang="en-EN">" xml:lang="en-EN" lang="en-EN">-counters apply the material under study in a thin layer on special films (acetate, colloidal, etc.) with a thickness of 10-15 μg/cm;vertical-align:super" xml:lang="en-EN" lang="en-EN">2" xml:lang="en-EN" lang="en-EN">. To increase the measurement accuracy (better than 10-15%), the substrate films are metalized by applying a metal layer using special sputtering installations, for example the universal vacuum sputtering installation UVR- 2. The thickness of the applied metal layer should be 5-7 μg/cm;vertical-align:super" xml:lang="en-EN" lang="en-EN">2" xml:lang="en-EN" lang="en-EN">. The conversion factor (K) in this case will be equal to 4.5;font-family:"Symbol"" xml:lang="en-EN" lang="en-EN">" xml:lang="en-EN" lang="en-EN">10;vertical-align:super" xml:lang="en-EN" lang="en-EN">-13" xml:lang="en-EN" lang="en-EN"> Ki/(imp/min).
Calculation method for measuring radioactivity
The calculation method is used if installations with end counters are used for measurement. To do this, the drugs are placed under the counter window at a distance of 20-30 mm from it. Low energy beta emitters should be placed at a distance of 6-7 mm from the counter. To compare the count rate with activity, a number of correction factors are introduced into the measurement results, taking into account radiation losses during radiometry.
" xml:lang="en-EN" lang="en-EN">Absolute activity of drugs A;vertical-align:sub" xml:lang="en-EN" lang="en-EN">pr" xml:lang="en-EN" lang="en-EN">(Ki) of thin and intermediate layers are determined by the formula:
" xml:lang="en-EN" lang="en-EN">" xml:lang="en-US" lang="en-US">N;vertical-align:sub" xml:lang="en-EN" lang="en-EN">0
" xml:lang="en-EN" lang="en-EN">A;vertical-align:sub" xml:lang="en-EN" lang="en-EN">pr" xml:lang="en-EN" lang="en-EN">=
" xml:lang="en-EN" lang="en-EN"> 2.22;font-family:"Symbol"" xml:lang="en-EN" lang="en-EN">" xml:lang="en-EN" lang="en-EN">10;vertical-align:super" xml:lang="en-EN" lang="en-EN">12;font-family:"Symbol"" xml:lang="en-US" lang="en-US">" xml:lang="en-US" lang="en-US">KP;font-family:"Symbol"" xml:lang="en-US" lang="en-US">" xml:lang="en-US" lang="en-US">mqr;vertical-align:super" xml:lang="en-EN" lang="en-EN">
" xml:lang="en-EN" lang="en-EN">where" xml:lang="en-US" lang="en-US">N;vertical-align:sub" xml:lang="en-EN" lang="en-EN">0" xml:lang="en-EN" lang="en-EN"> - drug counting rate (without background), imp/min;;font-family:"Symbol"" xml:lang="en-US" lang="en-US">" xml:lang="en-EN" lang="en-EN"> - coefficient taking into account the geometric factor of measurement;;font-family:"Symbol"" xml:lang="en-US" lang="en-US">" xml:lang="en-EN" lang="en-EN"> - correction for the resolution time of the counter; K - coefficient taking into account the absorption of beta radiation in the air layer and the material of the counter window; P - coefficient of self-absorption of beta radiation in drug material;;font-family:"Symbol"" xml:lang="en-US" lang="en-US">" xml:lang="en-EN" lang="en-EN"> - correction for gamma radiation for mixed radiation;" xml:lang="en-US" lang="en-US">m" xml:lang="en-EN" lang="en-EN"> mass of the measured drug;" xml:lang="en-US" lang="en-US">q" xml:lang="en-EN" lang="en-EN"> - coefficient taking into account the backscattering of beta radiation from the aluminum substrate;" xml:lang="en-US" lang="en-US">r;vertical-align:super" xml:lang="en-EN" lang="en-EN">" xml:lang="en-EN" lang="en-EN"> - correction for the decay scheme.
Coefficient r , taking into account the correction for the decay pattern, i.e., the relative content of beta radiation in the preparation, for many beta emitters is equal to 1. For potassium radionuclide-40, the coefficient g is 0.88, since out of 100% of decay events 88% occur beta decay, and 12% by K-capture, accompanied by gamma radiation.
When determining specific activity, the formula takes the form:
" xml:lang="en-EN" lang="en-EN"> 1;font-family:"Symbol"" xml:lang="en-EN" lang="en-EN">" xml:lang="en-EN" lang="en-EN">10;vertical-align:super" xml:lang="en-EN" lang="en-EN">6;font-family:"Symbol"" xml:lang="en-EN" lang="en-EN">" xml:lang="en-EN" lang="en-EN">" xml:lang="en-US" lang="en-US">N;vertical-align:sub" xml:lang="en-EN" lang="en-EN">0
" xml:lang="en-EN" lang="en-EN">A;vertical-align:sub" xml:lang="en-EN" lang="en-EN">pr" xml:lang="en-EN" lang="en-EN">=
" xml:lang="en-EN" lang="en-EN"> 2.22;font-family:"Symbol"" xml:lang="en-EN" lang="en-EN">" xml:lang="en-EN" lang="en-EN">10;vertical-align:super" xml:lang="en-EN" lang="en-EN">12;font-family:"Symbol"" xml:lang="en-US" lang="en-US">" xml:lang="en-US" lang="en-US">KP;font-family:"Symbol"" xml:lang="en-US" lang="en-US">" xml:lang="en-US" lang="en-US">mqr;vertical-align:super" xml:lang="en-EN" lang="en-EN">
where, 1 10 6 - conversion factor when converted to 1 kg when measuring m in mg.
Relative method for measuring radioactivity
The relative method for determining the radioactivity of drugs is based on comparing the count rate from a standard (a drug with known activity) with the count rate of the measured drug. The advantage of this method is simplicity, efficiency and satisfactory reliability. Radionuclides identical or similar in physical properties radionuclides contained in the measured preparations (radiation energy, decay pattern, half-life). Measurements of the standard and the preparation are carried out under the same conditions (on the same installation, with the same counter, at the same distance from the counter, on a substrate of the same material and the same thickness, the preparation and the standard must have the same geometric parameters: area, shape and thickness).
" xml:lang="en-EN" lang="en-EN">It is advisable to have a long-lived radioactive isotope as a standard, because it can be used long time without making amendments. During radiometry of object samples external environment containing beta-emitting radionuclides, potassium-40, strontium-90 + yttrium-90, T are used as a standard" xml:lang="en-US" lang="en-US">h" xml:lang="en-EN" lang="en-EN">-234. To prepare a standard from potassium-40, chemically pure salts KS1 or" xml:lang="en-US" lang="en-US">K;vertical-align:sub" xml:lang="en-EN" lang="en-EN">2" xml:lang="en-US" lang="en-US">SO;vertical-align:sub" xml:lang="en-EN" lang="en-EN">4" xml:lang="en-EN" lang="en-EN">.;vertical-align:sub" xml:lang="en-EN" lang="en-EN">" xml:lang="en-EN" lang="en-EN">First measure the counting speed from the standard" xml:lang="en-US" lang="en-US">N;vertical-align:sub" xml:lang="en-EN" lang="en-EN">et" xml:lang="en-EN" lang="en-EN"> then the counting speed from the drug" xml:lang="en-US" lang="en-US">N;vertical-align:sub" xml:lang="en-EN" lang="en-EN">pr" xml:lang="en-EN" lang="en-EN">. Based on the fact that the counting rate from the standard is proportional to the activity of the standard, and the counting rate from the drug is proportional to the activity of the drug, the radioactivity of the test drug is found.
And this N pr
A fl N fl = A pr N pr A pr =
" xml:lang="en-EN" lang="en-EN">" xml:lang="en-US" lang="en-US">N;vertical-align:sub" xml:lang="en-EN" lang="en-EN">et
" xml:lang="en-EN" lang="en-EN">where A;vertical-align:sub" xml:lang="en-EN" lang="en-EN">et" xml:lang="en-EN" lang="en-EN"> - standard radioactivity, dispersion/min; A;vertical-align:sub" xml:lang="en-EN" lang="en-EN">pr" xml:lang="en-EN" lang="en-EN"> - radioactivity of the drug (sample), dispersal/min;" xml:lang="en-US" lang="en-US">N;vertical-align:sub" xml:lang="en-EN" lang="en-EN">et" xml:lang="en-EN" lang="en-EN">- counting speed from the standard, imp/min;" xml:lang="en-US" lang="en-US">N;vertical-align:sub" xml:lang="en-EN" lang="en-EN">pr" xml:lang="en-EN" lang="en-EN"> - counting rate from the drug (sample), imp/min.
" xml:lang="en-EN" lang="en-EN">The comparative method gives satisfactory results in terms of accuracy if it is known that the radionuclide composition of the measured sample is the same or close to the reference one.
Send your good work in the knowledge base is simple. Use the form below
Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.
Posted on http://www.allbest.ru/
Radioactive medications
1. The concept of radioactive drugs
Radioactive drugs" (English radiopharmaceuticals; synonym: radiopharmaceuticals, radioindicators, radiopharmaceuticals (compounds, drugs)) - radioactive isotopes or their compounds with various inorganic or organic substances, intended for biomedical research, radioisotope diagnostics and treatment various diseases, mainly for radiation therapy malignant tumors.
For diagnostic purposes, radioisotopes are used, which, when introduced into the body, participate in the types of metabolism being studied or the activity of organs and systems being studied, and at the same time can be recorded by radiometric methods. Such radioactive drugs typically have a short effective half-life, resulting in negligible radiation exposure on the body of the subject.
Criteria for selecting radioactive drugs intended for radiation therapy malignant neoplasms, is the possibility of creating the required therapeutic dose ionizing radiation in the area of the tumor with minimal impact on surrounding healthy tissue. This effect is achieved by using radiopharmaceuticals in various states of aggregation and forms of delivery to the body (solutions, suspensions, granules, needles, wire, application bandages, etc.) and the use of isotopes that are most suitable in terms of the type and energy of radiation.
radioactive drug radiation
2 Classification
Radioactive drugs divided into open and closed:
· In sealed preparations, the radioactive material is enclosed in a protective coating or capsule to prevent radioactive contamination environment and contact with radioactive compounds of the patient and personnel.
· IN open drugs There is direct contact of the radioactive substance with body tissues and the environment.
In lech. For these purposes, certain open radiopharmaceuticals are also used. Some of them selectively accumulate in one or another pathol. hearth. For example, a solution of sodium iodide with radionuclide 131I is administered orally to treat thyrotoxicosis and tumor metastases thyroid gland. Others are directly injected into the tissue to be irradiated, e.g. colloidal solutions with radionuclides 32P, 90Y and 198Au - in lymph. vessels and cavities for the treatment of malignant tumors. The main active radiation factor in these cases is beta radiation (see Ionizing radiation), which allows irradiation of patol. lesion with minimal damage to surrounding tissue.
The choice of radionuclide for radiopharmaceuticals is determined by the main radiation-physical characteristics: half-life, which should, if possible, correspond to the duration diagnostic study; a type and energy spectrum of radiation that is convenient for detection and collimation and, if possible, does not have accompanying radiation that interferes with detection. The level of radiation exposure during radiodiagnostic procedures usually does not exceed thousandths of a gray, i.e., it does not pose a radiation hazard to the patient.
There is a group of open R. items, which are not injected into the body, but are used for radioimmunoassay of blood, urine, gastric juice and other body fluids. Such drugs, usually labeled with 125I, are used for quantification content of enzymes, hormones, vitamins and proteins, and the corresponding tests are simpler and more sensitive than conventional biochemical ones. methods.
In order to ensure radiation safety, when using any radioactive items, it is necessary to comply with the “Basic Sanitary Rules for Working with Radioactive Substances and Other Sources of Ionizing Radiation.”
3. List of radioisotopes used
|
Half life |
Type and energy of radiation [average value] |
Application |
|||
|
1731.9 keV |
|||||
|
1710.66 keV |
for interstitial and intracavitary radiation therapy of tumors; in the treatment of polycythemia and related disorders |
||||
|
1173.237 keV 1332.501 keV |
|||||
|
study of pulmonary function, central and peripheral hemodynamics, etc. |
|||||
|
2280.1 keV |
for interstitial and intracavitary radiation therapy (in the treatment of tumors of the female genital organs, cancer of the oral and lung mucosa, brain tumors, etc.) |
||||
|
diagnosis of brain tumors, study of central and peripheral hemodynamics, etc.; examination of the lungs, liver, brain, etc. |
|||||
|
171.28 keV 245.40 keV |
examination of the lungs, liver, brain, etc. |
||||
|
liver examination, etc. |
|||||
|
606.3 keV |
studies of iodine metabolism, lungs, brain, kidney function, liver, etc.; for the treatment of iodine-absorbing metastases of malignant thyroid tumors |
||||
|
346.0 keV |
study of pulmonary function, central and peripheral hemodynamics, etc. |
||||
|
672 keV (50.46%) |
in the treatment of tumors of the female genital organs, cancer of the oral and lung mucosa, brain tumors, etc. |
||||
|
535 keV (43.55%) |
|||||
|
468.0688 keV 316.50618 keV |
|||||
|
308.45507 keV 295.9565 keV 316.50618 keV |
|||||
|
examination of the lungs, liver, brain, etc.; for interstitial and intracavitary radiation therapy of tumors |
|||||
|
411.80205 keV |
4. History of radioactive drugs
From 1913, when a more or less inexpensive method for extracting radium was discovered, until the start of the war, radiation was perceived by people completely differently than it is now, and numerous scammers actively took advantage of this. Pharmacies sold radioactive soap, hand and face creams, toothpaste and powder with radium, drinks with thorium, special devices to add radium to drinking water, and in Europe and the USA there were radio spa centers where those being treated bathed in radioactive baths and inhaled the corresponding inhalations.
In fact, radiation can certainly be beneficial. Works found in his research that many doctors believe that radiation can treat cancer. Only success and failure have a ratio of approximately 1 to 100. The real usefulness of radiation began with the French scientist Henri Coutard, who demonstrated in 1922 World Congress oncology, that laryngeal cancer is on early stage can be suppressed by radioactive radiation in such a small dose that no side effects will be observed. It was based on the research of Claude Rego. The last one spent interesting experience on sterilization of a rabbit. The rabbit, irradiated with ordinary radioactive rays, was, of course, sterilized, but at the same time received serious injuries skin and some internal organs. But when dividing the same dose into several over several days, it led to sterilization - but without skin damage.
Coutard continued research in this direction and in 1934 (12 years later, we note!) presented to the public a technique that still forms the basis of radiation therapy today. He calculated radiation doses, duration, direction of effects on tumors - in general, I will not go into details, but the percentage of people for whom radiotherapy helped get rid of cancer increased thanks to Coutard to 23%. In 1935, his technique was officially introduced into oncology clinics.
There were other amazing radioactive things. For example, X-ray pedoscopes. It was produced by a company from the English city of St. Albans. A pedoscope (or shoe fluoroscope) was a box with X-ray machines installed inside. At the bottom there was a niche where the child for whom the shoes were bought would place his feet. There were eyepieces on top for both the child and the parents, through which they could look at the foot in the new shoe. The parents, thus, saw right through the baby’s foot - and understood whether the bones were comfortable inside the shoe, whether there was still room inside, otherwise the children often could not really tell whether it was tight or not tight. During the period of popularity (early 1950s), about 10,000 pedoscopes were installed in the world, but at the end of the 1950s they were banned in the USA, and a decade later - in Europe. The last 160 pedoscopes operated until 1960 in Switzerland.
Bibliography
1. Saksonov P.P., Shashkov V.S., Sergeev P.V. Radiation pharmacology. - M.: Medicine, 1976.
2. Bochkarev V.V. Radioactive drugs / Brief medical encyclopedia. -- 2nd ed. -- M.: Soviet Encyclopedia, 1989.
3. Big encyclopedic Dictionary. 2000
4. Medical encyclopedia 2009
Posted on Allbest.ru
Similar documents
Regulatory and technical documentation for medical products And pharmaceuticals, basic requirements for its preparation and design, areas and features practical application. Systemic classification of obstetric and gynecological instruments.
test, added 07/18/2011
History of the discovery of radioactivity. Types of ionizing radiation. Consequences of radiation on health. Radioactive medicinal preparations. Aspects of the use of radiation for diagnosis, treatment, sterilization medical instruments, blood circulation studies.
presentation, added 10/30/2014
General concept about generics. Features of patent protection of original drugs. The difference between a copied drug and a generic. Pharmaceutical, biological and therapeutic equivalence generics. Bioequivalent drugs.
abstract, added 10/18/2011
Metabolic drugs. Nootropic and normothimic drugs: classification, methods of production. Mechanism of biological activity. Neurotransmitters and related theories. Medical indications use of nootropic drugs.
course work, added 01/28/2008
The use of sulfonamides, co-trimoxazole, quinolones, fluoroquinolones and nitrofurans in clinical practice. The mechanism of action of drugs, the spectrum of their activity, pharmacokinetic features, contraindications, drug interactions and testimony.
presentation, added 10/21/2013
Classification of anti-tuberculosis drugs by the International Union Against Tuberculosis. Combination of isoniazid and rifampicin. Isonicotinic acid hydrazide preparations. Combined anti-tuberculosis drugs, their drug interactions.
presentation, added 10/21/2013
Study of the characteristics, classification and prescription of drugs that are used in the treatment of atherosclerosis. Study of the range of anti-sclerotic drugs and the dynamics of turning to the pharmacy for drugs in this group.
course work, added 01/14/2018
Normal and pathological physiology. Emetic and antiemetic drugs. History of discovery, classification, mechanism of biological activity, methods of production (synthesis) and analysis of emetic and antiemetic drugs.
course work, added 10/22/2008
Medicines for correction of dysfunctions reproductive system. Preparations of female and male sex hormones and their synthetic analogues. Classification of sex hormone preparations. Release form and mechanism of action of hormonal drugs.
presentation, added 03/15/2015
Medicinal compounds used to treat and prevent diseases. Inorganic and organic medicinal substances. Antimicrobial, analgesic, antihistamine, antitumor drugs affecting the heart and blood vessels.
There are radioactive drugs for biomedical research, diagnostic, therapeutic, and radiation sources for gamma devices.
Hundreds of inorganic and organic compounds labeled with 14C, 3H, 32P, 35S, 131J and other radioactive isotopes can be used in biomedical research. Highest value have labeled amino acids, their analogs and derivatives, alkaloids, vitamins, antibiotics, carbohydrates and their derivatives, nucleic acid components, steroids and steroid hormones.
To label diagnostic radioactive drugs, as a rule, radioactive isotopes with a short half-life are used. In the case of labeling with long-lived isotopes, compounds that are quickly eliminated from the body are used (vitamin B12-Co58, neohydrin-Hg2O3, etc.). Some diagnostic short-lived radioactive preparations with the isotopes yttrium-90, technetium-99m, iodine-132, gallium-68, indium-115m are obtained through simple manipulations directly in medical institutions from special generators as daughter products of the decay of the corresponding long-lived radioactive isotopes. Diagnostic radioactive drugs are labeled with gamma, beta and positron emitters. Radioactive drugs that emit alpha particles are not suitable for this purpose. Radioactive drugs are used in the form of true and colloidal solutions, suspensions, proteins, fats, gases, etc. Therapeutic radioactive drugs are intended for radiation therapy of mainly malignant tumors, as well as some skin diseases. These include dispersed radioactive drugs (colloidal solutions, suspensions, emulsins), discrete radiation sources (applicators, point and linear sources-drugs that are absorbed in the body), organotropic and tumorotropic substances (chemical elements with tropism for certain organs and tissues, antibodies , complexing agents, etc.). Beta- and gamma-active isotopes (60Co, 137Cs, 32P, 90Sr, 90Y, 198Au, etc.) are used in therapeutic radioactive preparations. In some cases, these drugs make it possible to provide irradiation of the tumor in a sufficient tissue dose with minimal radiation exposure to surrounding healthy tissue. Depending on the location of the pathological focus, radioactive drugs are used in the form of applications to the skin and mucous membranes or injected into tissues, cavities, intravenously or into lymphatic vessels. To charge gamma therapy devices, sources made from cobalt-60 and cesium-137 are used. They have the most advantageous properties for gamma therapy: a relatively long half-life, monochromaticity and high energy of gamma radiation, and a more favorable deep distribution of absorbed energy in the irradiated tissues compared to conventional X-ray radiation.
The same isotopes are used in installations for radiation sterilization.
The radioactivity of drugs can be determined by the absolute, calculated and relative (comparative) method. The latter is the most common.
Absolute method. A thin layer of the material under study is applied to a special thin film (10-15 μg/cm²) and placed inside the detector, as a result of which the full solid angle (4p) is used to register emitted beta particles, for example, and almost 100% counting efficiency is achieved. When working with a 4p counter, you do not need to introduce numerous corrections, as with the calculation method.
The activity of the drug is expressed immediately in units of activity Bq, Ku, mKu, etc.
The absolute activity of alpha and beta emitting isotopes is determined using a calculation method using conventional gas-discharge or scintillation counters.
A number of correction factors are introduced into the formula for determining the activity of a sample, taking into account radiation losses during measurement.
A = N/w×e×k×r×q×r×g m×2.22×10¹²
A is the activity of the drug in Ku;
N is the counting rate in pulses/min minus the background;
w - correction for geometric measurement conditions (solid angle);
e- correction for the resolution time of the counting installation;
k - correction for absorption of radiation in the air layer and in the window (or wall) of the counter;
r - correction for self-absorption in the drug layer;
q - correction for backscattering from the substrate;
r - correction for the decay scheme;
g - correction for gamma radiation with mixed beta - gamma radiation;
m is the weighed portion of the measuring preparation in mg;
2.22×10¹² - conversion factor from the number of disintegrations per minute to Ci (1 Ci = 2.22*10¹² disintegrations/min).
To determine the specific activity, it is necessary to convert the activity per 1 mg to 1 kg.
Aud = A*106, (Ku/kg)
Preparations for radiometry can be prepared with a thin, thick or intermediate layer of the material being studied.
If the material under study has a half-attenuation layer - D1/2,
then thin - at d<0,1D1/2, промежуточные -
0,1D1/2
All correction factors themselves, in turn, depend on many factors and, in turn, are calculated using complex formulas. Therefore, the calculation method is very labor-intensive.
The relative (comparative) method has found wide application in determining the beta activity of drugs. It is based on comparing the count rate from a standard (a drug with known activity) with the count rate of the measured drug.
In this case, there must be completely identical conditions when measuring the activity of the standard and the test drug.
Apr = Aet* Npr/Net, where
Aet is the activity of the reference drug, dispersion/min;
Apr - radioactivity of the drug (sample), dispersion/min;
Net - counting speed from the standard, imp/min;
Npr - counting rate from the drug (sample), imp/min.
Data sheets for radiometric and dosimetric equipment usually indicate the error with which measurements are made. The maximum relative measurement error (sometimes called the main relative error) is indicated as a percentage, for example ± 25%. For different types of instruments it can be from ± 10% to ± 90% (sometimes the error of the type of measurement for different sections of the scale is indicated separately).
Based on the maximum relative error ± d%, the maximum absolute measurement error can be determined. If readings from instrument A are taken, then the absolute error is DA=±Ad/100. (If A = 20 mR, and d = ±25%, then in reality A = (20 ± 5) mR. That is, in the range from 15 to 25 mR.
- Veterinary and sanitary examination of milk and eggs for radiation injuries.
Entering the body of animals, radioisotopes begin to be eliminated from it in significant quantities already in the first hours and days, appearing in feces, urine, milk, eggs, and wool. It has been established that cows can excrete with milk: iodine-131 - up to 8% of the dose received, strontium-90 - up to 1.9%, cesium-137 - up to 9.3. In cows with a daily milk yield of 15-20 kg, the relative amount of isotopes is greater than in low-yielding cows. The release of isotopes also increases when feeding animals succulent feed (sometimes by 70%), and when feeding beets, rutabaga and other vegetables of the cabbage family containing thiacyanate, the excretion of iodine-131 decreases. According to G.K. Vokken (1973), the introduction of stable iodine into the diet up to 2.0 g per day. can reduce the yield of iodine-131 in milk by 50%. At the same time, the susceptibility of the thyroid gland is reduced. The excretion of strontium-90 is greater in the first months of lactation.
Radiation injuries significantly affect the productivity of dairy animals and the composition of milk. When cows are internally irradiated with a dose of 3 Ci, milk yield decreases by 33% on the first day, by 52% on the 10th day, and by 85% on the 30th day (N.N. Akimov, V.G. Ilyin, 1984). In case of severe radiation sickness from external irradiation by 7 days. productivity drops by 50% within a few days. until death - stops completely.
The composition of milk also changes: SNF (1.5 times), specific gravity, acidity, and amount of calcium increase; fat content is reduced (by 20%) and antibacterial properties. During the veterinary and sanitary assessment of milk from animals suffering from radiation sickness caused by internal irradiation, radiometric data are additionally taken into account. If the maximum permissible levels of contamination of milk with radioisotopes are exceeded, it is subject to decontamination. The same is done with the milk of healthy animals that have been subjected to mechanical contamination with radioactive substances during storage or
Transportation induced by radioactivity. Milk obtained from animals suffering from radiation sickness from external irradiation, with a positive overall assessment of its good quality, can be used without restrictions.
Radioisotopes of iodine-131 and strontium-90 are 80-90% associated with the protein fraction of milk, cesium-137 is in ionic form. These data are of significant importance when decontaminating milk.
This results in relatively clean butter and cottage cheese. The serum is assessed as confiscated, subject to either further decontamination through ion exchange resin filters, or dilution with “clean” serum to acceptable levels of radioactivity and feeding to animals. A reduction in the radioactivity of milk due to the decay of short-lived isotopes during long-term storage can be achieved by processing it into condensed and dry milk. If milk is contaminated with long-lived isotopes, it is deactivated by filtration through ion exchange resins or ionite separation.
Without the danger of causing radiation damage to animals, animals can be grazed at a radiation level of 0.5 R/h, but to obtain milk uncontaminated with radioisotopes - only at a radiation level of 0.1 R/h.
In case of contact contamination with radioisotopes (deposition on the surface of finished products), solid dairy products, butter, cheeses, etc., their decontamination is carried out by cutting off the surface layer to a depth of 2-3 mm. This is done with thin steel wire, a long knife or scraper. After that, control dosimetry of the product is carried out.
The ovary of chickens is a critical organ for iodine-131, equivalent to the thyroid gland, therefore, when RV enters the body of chickens, up to 3.25% of the radioiodine introduced into the body is deposited in the yolk of the egg. Up to 9.25% of cesium-137 will be deposited in the protein, and up to 37.5% of strontium-89 and strontium-90 will be deposited in the shell. In total, the activity of the egg can be up to 50% of the total activity of the daily dose in the first day after the explosion. On the 19th day, if we take the activity of the egg as 100%, it will change as follows: strontium will account for 93.4%, cesium - 2.9, iodine - 3.7%.
Contamination of the shell with strontium can also be mechanical (on the surface) during the passage of the egg through the cloaca, where the unreserved part of strontium enters with feces.
With a single dose of 3 mCi/kg, egg laying may stop on the 19th day. If the same dose is administered fractionally over 10 days, egg laying stops after 41 days.
Eggs are decontaminated due to the self-disintegration of isotopes during long-term storage. Taking into account the tropism of certain isotopes to different parts of the egg and their different physical decay constants, the white and yolk are processed separately into egg powder and stored until the activity declines within acceptable values. In this case, the radioactivity of the egg white decreases 10 times in 43 days, and the yolk - in 14 days. storage Egg shells, which contain a significant amount of strontium-90, pose a risk of repeated internal irradiation of chickens due to their consumption, which is possible if there is a lack of calcium in the diet. It is best to bury it with a layer of soil covering at least 70 cm and installing a sign in this place “Infected with RV. Date and radiation level.” (In peacetime, all contaminated waste is disposed of in the manner prescribed by special instructions.)
In the case of external irradiation of chickens, egg laying remains almost unchanged. With severe radiation sickness, it stops with the onset of peak time. Eggs obtained from chickens under external irradiation are released for food purposes without restrictions.
According to V.A. Verkholetov and V.P. Frolov, in the hair follicles, sebaceous glands and other elements of the skin when animals are irradiated, structural and morphological changes of atrophic order occur, which with external irradiation lead to hair loss (wool), especially in sheep. These changes contribute to a decrease in the quality of hides and wool. Thus, with mild and moderate degrees of radiation sickness, the incorporation of iodine-131 reduces the shearing of wool, its density, length, fineness, thickness and strength of sheepskin. When radioisotopes come into direct contact with the skin, beta burns occur. If animals are internally irradiated, the skin contains a significant amount of isotopes that create an activity almost equal to the specific activity of muscle tissue. A certain amount of isotopes (less than in the skin) is also deposited in the hair. Consequently, skin and wool are subject to radiometric and dosimetric control.
The main method of decontamination of wool is the self-disintegration of isotopes during long-term storage, and for hides, in addition, wet salting or pickling.
Radiation can be used either to assess the metabolism of the isotope-labeled substance in the body, or to inhibit tissues that have absorbed the isotope. Designed for biomedical research, radioisotope diagnostics and treatment of various diseases, mainly for radiation therapy of malignant tumors.
For diagnostic purposes, radioisotopes are used, which, when introduced into the body, participate in the types of metabolism being studied or the activity of organs and systems being studied, and at the same time can be recorded by radiometric methods. Such radioactive drugs, if possible, have a short effective half-life and low-energy radiation that is weakly absorbed in tissues, which causes an insignificant radiation load on the body of the subject.
The criterion for choosing radioactive drugs intended for radiation therapy of malignant tumors is the ability to create the necessary therapeutic dose of ionizing radiation in the area of the tumor with minimal impact on healthy tissue. This effect is achieved both by choosing the type and duration of irradiation and by choosing the method of delivering the radiopharmaceutical to the target. Delivery is possible both through the body’s metabolism with selective accumulation of the radioactive isotope in the tissues to be irradiated, and by surgical means in the form of granules, probes, application dressings, etc.
Classification
Radioactive drugs are divided into open and closed:
- IN closed In preparations, the radioactive material is enclosed in a protective coating or capsule that prevents radioactive contamination of the environment and contact with the radioactive compound of the patient and personnel.
- IN open In preparations, direct contact of the radioactive substance with body tissues and the environment occurs.
List of radioisotopes used
| Isotope | Half life | Type and energy of radiation [average value] | Application | |
|---|---|---|---|---|
| 11 C | 20,385 min | β+ | 1982.1 keV |
Diagnostics using . Metabolic state of the heart, assessment of amino acid consumption (methionine, leucine) and protein synthesis, diagnosis of brain tumors, assessment of the metabolic state of the parathyroid gland, rate of metabolism of fatty acids in the myocardium |
| 13N | 9.97 min | β+ | 1200.3 keV | Diagnosis using positron emission tomography. Blood flow measurement, myocardial perfusion assessment |
| 15 O | 122.24 s | β+ | 1731.9 keV |
Diagnosis using positron emission tomography. Study of lung function, central and peripheral hemodynamics, etc. |
| 18 F | 109,771 min | β+ | 633.5 keV | Diagnosis using positron emission tomography. Visualization of tumors of various locations, assessment of glucose metabolism in the myocardium, lungs, brain, diagnosis of Alzheimer's disease, diagnosis of diffuse Lewy body disease, diagnosis of Parkinson's disease, localization of the epileptic focus. |
| 32P | 14,262 days | β− | 1710.66 keV |
Interstitial and intracavitary radiation therapy of tumors; treatment of polycythemia and related disorders. 33 P can be used for the same purposes. |
| 60Co | 5.2714 years | β− | 317.88 keV | in the treatment of tumors of the female genital organs, cancer of the oral and lung mucosa, brain tumors, etc. |
| γ | 1173.237 keV 1332.501 keV |
|||
| 85 Kr | 10,756 years | β− | 687.4 keV | study of pulmonary function, central and peripheral hemodynamics, etc. |
| 90 Y | 64.1 hours | β− | 2280.1 keV |
for interstitial and intracavitary radiation therapy (in the treatment of tumors of the female genital organs, cancer of the oral and lung mucosa, brain tumors, etc.) |
| 99m Tc | 6.01 hours | γ | 140.511 keV | Diagnosis of brain tumors using gamma cameras, study of central and peripheral hemodynamics, etc.; examination of the lungs, liver, brain, etc. |
| 111 In | 2.8047 days. | γ | 171.28 keV 245.40 keV |
examination of the lungs, liver, brain, etc. |
| 113m In | 1.6582 h. | γ | 391.69 keV | liver examination, etc. |
| 123 I | 13 hours | γ | 160 keV | Diagnosis using gamma cameras of the thyroid gland and nervous system of the heart. |
| 125 I | 59.5 days | γ | 35 keV | Treatment of prostate cancer using the method |
This examination method is based on the ability of radioactive isotopes to emit. Nowadays, computer radioisotope research is most often performed - scintigraphy. First, the patient is injected with a radioactive substance into a vein, into the mouth, or by inhalation. Most often, compounds of the short-lived isotope technetium with various organic substances are used.
Radiation from the isotopes is captured by a gamma camera, which is placed above the organ being examined. This radiation is converted and transmitted to a computer, on the screen of which an image of the organ is displayed. Modern gamma cameras make it possible to obtain layer-by-layer “slices”. The result is a color picture that is understandable even to non-professionals. The study is carried out for 10-30 minutes, and all this time the image on the screen changes. Therefore, the doctor has the opportunity to see not only the organ itself, but also observe its work.
All other isotope studies are gradually being replaced by scintigraphy. Thus, scanning, which before the advent of computers was the main method of radioisotope diagnostics, is used less and less today. When scanning, the image of the organ is displayed not on a computer, but on paper in the form of colored shaded lines. But with this method, the image turns out flat and also provides little information about the functioning of the organ. And the scanning causes certain inconvenience for the patient - it requires him to be completely immobile for thirty to forty minutes.
Right on target
With the advent of scintigraphy, radioisotope diagnostics received a second life. This is one of the few methods that detects the disease at an early stage. For example, cancer metastases in bones are detected by isotopes six months earlier than by x-ray. These six months can cost a person his life.
In some cases, isotopes are generally the only method that can give the doctor information about the condition of the diseased organ. With their help, kidney diseases are detected when nothing is detected on an ultrasound; microinfarctions of the heart, invisible on an ECG and echocardiogram, are diagnosed. Sometimes a radioisotope study allows the doctor to “see” pulmonary embolism, which is not visible on an x-ray. Moreover, this method provides information not only about the shape, structure and structure of the organ, but also allows you to assess its functional state, which is extremely important.
If previously only the kidneys, liver, gallbladder and thyroid gland were examined using isotopes, now the situation has changed. Radioisotope diagnostics is used in almost all areas of medicine, including microsurgery, neurosurgery, and transplantology. In addition, this diagnostic technique allows not only to make and clarify the diagnosis, but also to evaluate the results of treatment, including constant monitoring of postoperative patients. For example, scintigraphy is indispensable when preparing a patient for coronary artery bypass surgery. And in the future it helps to evaluate the effectiveness of the operation. Isotopes detect conditions that threaten human life: myocardial infarction, stroke, pulmonary embolism, traumatic brain hemorrhages, bleeding and acute diseases of the abdominal organs. Radioisotope diagnostics helps to distinguish cirrhosis from hepatitis, discern a malignant tumor at the first stage, and identify signs of rejection of transplanted organs.
Under control
There are almost no contraindications to radioisotope research. To carry it out, an insignificant amount of short-lived isotopes that quickly leave the body is introduced. The amount of the drug is calculated strictly individually, depending on the patient’s weight and height and the condition of the organ being studied. And the doctor must select a gentle examination regimen. And most importantly: radiation exposure during a radioisotope study is usually even less than during an x-ray study. Radioisotope testing is so safe that it can be performed several times a year and combined with x-rays.
In case of an unexpected breakdown or accident, the isotope department in any hospital is reliably protected. As a rule, it is located far from the medical departments - on the ground floor or in the basement. The floors, walls and ceilings are very thick and covered with special materials. The stock of radioactive substances is located deep underground in special lead-lined storage facilities. And the preparation of radioisotope preparations is carried out in fume hoods with lead screens.
Constant radiation monitoring is also carried out using numerous counters. The department employs trained personnel who not only determine the level of radiation, but also know what to do in the event of a leak of radioactive substances. In addition to the department employees, the radiation level is monitored by specialists from SES, Gosatomnadzor, Moskompriroda and the Department of Internal Affairs.
Simplicity and reliability
The patient must adhere to certain rules during a radioisotope study. It all depends on which organ is supposed to be examined, as well as on the age and physical condition of the sick person. Thus, when examining the heart, the patient must be prepared for physical activity on a bicycle ergometer or on a walking track. The study will be of better quality if done on an empty stomach. And, of course, you should not take medications several hours before the test.
Before the bone scintigraphy, the patient will have to drink a lot of water and urinate frequently. This flushing will help remove isotopes from the body that have not settled in the bones. When examining your kidneys, you also need to drink plenty of fluids. Scintigraphy of the liver and biliary tract is done on an empty stomach. And the thyroid gland, lungs and brain are examined without any preparation at all.
Radioisotope testing may be interfered with by metal objects placed between the body and the gamma camera. After introducing the drug into the body, you must wait until it reaches the desired organ and is distributed in it. During the examination itself, the patient should not move, otherwise the result will be distorted.
The simplicity of radioisotope diagnostics makes it possible to examine even extremely sick patients. It is also used in children starting from the age of three; they mainly examine the kidneys and bones. Although, of course, children require additional training. Before the procedure, they are given a sedative so that they do not fidget during the examination. But pregnant women are not subject to radioisotope testing. This is due to the fact that the developing fetus is very sensitive to even minimal radiation.
Loading...