Considerable medical research is being conducted worldwide into the use of radionuclides attached to highly specific biological chemicals such as immunoglobulin molecules monoclonal antibodies. The eventual tagging of these cells with a therapeutic dose of radiation may lead to the regression — or even cure — of some diseases. Many medical products today are sterilized by gamma rays from a Co source, a technique which generally is much cheaper and more effective than steam heat sterilization.
The disposable syringe is an example of a product sterilized by gamma rays. Because it is a 'cold' process radiation can be used to sterilize a range of heat-sensitive items such as powders, ointments, and solutions, as well as biological preparations such as bone, nerve, and skin to be used in tissue grafts. Large-scale irradiation facilities for gamma sterilization are installed in many countries. Smaller gamma irradiators, often utilising Cs, having a longer half-life, are used for treating blood for transfusions and for other medical applications.
Sterilization by radiation has several benefits. It is safer and cheaper because it can be done after the item is packaged. The sterile shelf-life of the item is then practically indefinite provided the seal is not broken. Irradiation technologies are used to sterlize almost half of the global supply of single-use medical products.
Apart from syringes, medical products sterilized by radiation include cotton wool, burn dressings, surgical gloves, heart valves, bandages, plastic, and rubber sheets and surgical instruments. Most medical radioisotopes made in nuclear reactors are sourced from relatively few research reactors , including:.
Of fission radioisotopes, the vast majority of demand is for of Mo for Tcm. However, NRU ceased production in October , and the other two have limited remaining service life.
Output from each varies due to maintenance schedules. Supply capacity is always substantially e. One challenge is the delivery of fresh supplies in weekdays, in line with demand, to minimize waste. In it was planning to build a RUR 6 billion radiopharmaceutical plant near Moscow. About half of its radioisotope production is exported. The targets are then processed to separate the Mo and also to recover I However, in medical imaging, the cost of Mo itself is small relative to hospital costs.
Mo can also be made by bombarding Mo with neutrons in a reactor. There are three ways to produce Mo The most common and effective method is by fission of uranium in a target foil, followed by chemical separation of the Mo. This fission is done in research reactors. A second method is neutron activation, where Mo in target material captures a neutron.
A third method is by proton bombardment of Mo in an accelerator of some kind. There are plans to produce it by fission in a subcritical assembly in an accelerator. A number of incidents in pointed out shortcomings and unreliability in the supply of medical isotopes, particular technetium.
As indicated above, the world's supply of Mo comes from just six reactors, five of which are over 50 years old. The Canadian and Netherlands reactors required major repairs over and were out of action for some time. Osiris was due to shut down in but apparently continued to at least An increasing supply shortfall of technetium was forecast from , and the IAEA encouraged new producers.
Also, the processing and distribution of isotopes is complex and constrained, which can be critical when the isotopes concerned are short-lived. A need for increased production capacity and more reliable distribution is evident. It reviewed the Mo supply chain to identify the key areas of vulnerability, the issues that need to be addressed, and the mechanisms that could be used to help resolve them. It requested an economic study of the supply chain, and this was published in by the NEA.
The report identifies possible changes needed. The NEA report predicted supply shortages from , not simply from reactors but due to processing limitations too. Historically reactor irradiation prices have been too low to attract new investment, and full cost recovery is needed to encourage new infrastructure. Transport regulation and denial of shipment impede reliable supply.
Outage reserve capacity needs to be sourced, valued, and paid for by the supply chain. Fission is the most efficient and reliable means of production, but Canada and Japan are developing better accelerator-based techniques.
A review of the situation in mid showed that the market had substantially restructured following the supply crisis, and that restructuring had led to increased efficiencies in the use of material at the different layers in the supply chain. The latest NEA data confirms a relatively flat market demand of around six-day TBq Mo per week at the end of radiochemical processing.
In addition, several sources of supply had ramped up production to lift the baseline supply capacity for the and periods to a level safely above the revised market demand. Also it called for proposals for an LEU-based supply of Mo for the US market, reaching six-day TBq per week by mid, a quarter of world demand.
Tenders for this closed in June , but evidently no immediate progress was made. In December Congress passed the American Medical Isotope Production Act of to establish a technology-neutral program to support the production of Mo for medical uses in the USA by non-federal entities.
In February , the Department of Energy's National Nuclear Security Administration NNSA selected four companies to begin negotiations for potential new cooperative agreement awards for the supply of molybdenum, mostly from accelerators. Niowave is developing superconducting electron linear accelerators, NorthStar Medical Radioisotopes is planning to irradiate Mo targets to produce Mo in a reactor, while in the longer term it is developing a method using a linear accelerator.
See below for fuller descriptions. Such Mo has relatively low specific activity, and there are complications then in separating the Tc The company received approval to begin routine production in August , and aims eventually to meet half of US demand with six-day TBq per week. MURR runs on low-enriched uranium. Longer-term NorthStar is considering a non-reactor approach. In , NorthStar Medical Radioisotopes signed an agreement with Westinghouse to investigate production of Mo in nuclear power reactors using its Incore Instrumentation System.
It is aiming to set up a 44, m 2 radioisotope production facility in Columbia, Missouri. The NRC approved the plans in May However, Nordion withdrew from the project in April citing delays and cost overruns that had increased the project's commercial risk. An earlier proposal for Mo production involving an innovative reactor and separation technology has lapsed.
They planned to use Aqueous Homogeneous Reactor AHR technology with LEU in small kW units where the fuel is mixed with the moderator and the U forms both the fuel and the irradiation target.
As fission proceeds the solution is circulated through an extraction facility to remove the fission products with Mo and then back into the reactor vessel, which is at low temperature and pressure.
In mid Los Alamos National Laboratory announced that it had recovered Mo from low-enriched sulphate reactor fuel in solution, raising the prospect of this process becoming associated with commercial reprocessing plants as at La Hague in France. JSC Isotope was founded in and incorporated in Brazil is a major export market. Its product portfolio includes more than 60 radioisotopes produced in cyclotrons, nuclear reactors by irradiation of targets, or recovered from spent nuclear fuel, as well as hundreds of types of ionizing radiation sources and compounds tagged with radioactive isotopes.
It has more than 10, scientific and industrial customers for industrial isotopes in Russia. The Karpov Institute gets some supply from Leningrad nuclear power plant. Australia's Opal reactor has the capacity to produce half the world supply of Mo, and with the ANSTO Nuclear Medicine Project will be able to supply at least one-quarter of world demand from Tcm or Mo can also be produced in small quantities from cyclotrons and accelerators, in a cyclotron by bombarding a Mo target with a proton beam to produce Tcm directly, or in a linear accelerator to generate Mo by bombarding an Mo target with high-energy X-rays.
It is generally considered that non-reactor methods of producing large quantities of useful Tc are some years away. At present the cost is at least three times and up to ten times that of the reactor route, and Mo is available only from Russia. If Tc is produced directly in a cyclotron, it needs to be used quickly, and the co-product isotopes are a problem. An LEU target solution is irradiated with low-energy neutrons in a subcritical assembly — not a nuclear reactor.
The neutrons are generated through a beam-target fusion reaction caused by accelerating deuterium ions into tritium gas, using a particle accelerator. SHINE is an acronym for 'subcritical hybrid intense neutron emitter'.
Because energy must be released in order for decay to take place at all. The alpha particle has very stable and high binding energy, has tightly bound structure, and can be emitted spontaneously with positive energy in alpha decay, whereas 2 H, 3 H, and 3 He decay would require an input energy. The parent nucleus Z, A is transformed via. Beta particles are fast electron or positron; these are originated from weak interaction decay of a neutron or proton in nuclei, which contains an excess of the respective nucleon.
In a neutron-rich nucleus, neutron can transform itself in to a proton by emission of beta particles and antineutrino. Similarly, in the nuclei with rich proton, it transforms into neutron by emission of neutrino and positron. These radiations are high penetrating and less ionizing power:. The emission of gamma rays is usually the most common mode of nuclear excitation and also occurs through internal conversion. X-rays arises from the electron cloud surrounding the nucleus.
They were discovered by Roentgen in X-rays are produced in X-ray tube by fast moving electron which is suddenly stopped by target. These charged particles produce the ionization. It has more penetrating than gamma ray and can be stopped by thin concrete or paraffin barrier. They are produced by nuclear reaction and spontaneous fission in nuclear reactors.
Depending on its effects on matter and its ability to ionize the matter, radiation is classified in two main categories: ionizing and nonionizing radiations. Radiation passing through the matter which breaks the bonds of atoms or molecules by removing the electron is called ionization radiation.
It passes through the matter or living organisms, and it produces various effects. Ionizing radiation is produced by radioactive decay, nuclear fission, and fusion, by extremely hot objects, and by particle accelerators. The emission of ionizing radiation is explained in Section 2.
The ionizing radiation is again divided into two types: direct and indirect ionizing radiation. Indirectly ionizing radiation deposits energy in the medium through a two-step process; in the first step, charged particles are released in the medium. Nonionizing radiation is part of the electromagnetic radiation where there is insufficient energy to cause ionization. But it has sufficient energy only for excitation and not to produce ions when passing through matter [ 4 ].
Radiowaves, microwaves, infrared, ultraviolet, and visible radiation are the examples of nonionizing radiations. Nonionizing radiation is essential to life, but excessive exposures will cause biological effects. The radiation that exits all around us is called natural background radiation. All living organisms including man have been continuously exposed to ionizing radiations emitted from different sources, which always existed around us.
The sources of natural radiation are cosmic rays and naturally occurring primordial radionuclides such as U, Th, U, and their decay products as well as the singly occurring natural radionuclides like 40 K and 87 Rb, which are present in the earth crust, soil, rocks, building materials, ore, and water in the environment [ 5 , 6 ]. Background radiation is a constant source of ionizing radiation present in the environment and emitted from a variety of sources.
Natural radiations originated from three major sources: terrestrial, extraterrestrial, and internal intake of natural radionuclides and their daughter product sources of radiation. Terra means earth; the radiation originated from the earth crust is called terrestrial radiation. The primordial radionuclides U, Th, and 40 K present in varying amounts in soil, rocks, water, and atmosphere are the sources of terrestrial radiation. The bulk of the natural radiation is mainly due to 40 K and U, Th, and their decay products [ 7 ].
Natural uranium consists of three isotopes U, U, and U. Thorium is one of the important natural primordial radionuclides with a half-life of 1. It is about four times more abundant in nature than uranium.
Average crustal abundance of Th is 7. All substances found in the terrestrial system contain variable amounts of U and Th; they undergo radioactive decay until they become stable isotopes. The two main important radioactive series are given in Tables 2 and 3.
The bulk of natural radiation comes from the primordial radionuclides such as U, U and Th. They decay into other radioactive isotope as a part of radioactive series. These series are naturally occurring radioactive series, which have existed since the earth was formed. These radioisotopes are chemically bound to minerals in rocks and soils and pose no biological hazards except radon, thoron and its progeny.
Radon and thoron are noble radioactive gases, the higher concentrations of these gases and progenies are inhaled to produce lung cancer.
Decay series of uranium U [ 8 ]. Decay series of thorium Th [ 8 ]. The decay series of uranium and the type of radiation and range of energy of decay products are shown in Table 2 [ 8 ].
The important daughter product of uranium series is radon and its progenies. Radon is a naturally occurring radioactive gas. This was discovered by F. Dorn in It is found everywhere as part of our environment i. The ubiquitous radioactive gas is formed by radioactive decay of radium Ra , which is the daughter product of uranium decay series Table 2. The half-life of radon is 3.
These are the significant contributor of natural radiation [ 9 ]. On the basis of the epidemiological studies, it has been established that the enhanced levels of indoor radon in dwellings can cause health hazards and may lead to serious diseases like lung cancer in human beings [ 5 , 10 ]. The decay series of thorium and types of radiation with range of energies of decay products are as shown in Table 3 [ 11 ].
The important daughter products in this series are thoron and its progenies. The thoron progeny has relatively long half-life than that of radon progeny; therefore thoron progeny would give a significant dose to the lungs [ 11 , 12 , 13 ]. The decay of thorium Th leads to the subsequent formation of thoron Rn , its half-life 55 seconds. It is more abundant than U, but the short half-life of Rn allows only a fraction to escape into the atmosphere.
The Rn is the one of the most significant isotope and it contributes significant dose to publics as ionizing radiation. Potassium is the most common of the naturally occurring non-series, singly occurring primordial radionuclides. Natural potassium comprises three isotopes 39 K Among the three naturally occurring potassium isotopes, only 40 K is radioactive with a half-life of 1.
The remaining This latter decay branch also emits a characteristic gamma ray at 1. This line is very useful to identify and quantify 40 K by gamma spectrometry [ 14 ]. Potassium is present in the earth crust with varying amounts and also present in almost all plant and animal tissues.
Most of the potassium occurs in earth crust as minerals such as feldspar, orthoclase, muscovite, and biotite micas. Human beings require potassium to sustain their biological processes. A person who weighs 70 kg has about g of potassium in his body which has activity of 4 kBq, most of which is located in the muscle. The absorbed dose per year is about 0. Upon ingestion, 40 K then moves quickly from the gastrointestinal track into the bloodstream. The 40 K quickly enters the bloodstream and distributed to all organs and tissues.
Each year, this isotope delivers doses of about 18 millirem mrem to soft tissues of the body and 14 mrem to the bone. The extraterrestrial radiations or cosmic radiations are high energetic radiations or subatomic particles, mainly originated from the sun, stars, collapsed stars such as neutron stars , quasars, and the hot galactic and intergalactic plasma. The earth and all living things on it are constantly bombarded by these radiations from space.
These radiations have extremely high energies that vary from 10 2 MeV to more than 10 14 MeV [ 16 ]. The cosmic radiations are much more intense in the upper troposphere. Cosmic radiation dose increases with altitude; at 2. Therefore, the annual effective doses from cosmic ray radiation around the world are estimated to range between 0. The alpha and beta radiation emitted by these radioactive materials poses serious health threat if significant quantities are inhaled or injected.
In addition to natural background radiation, human beings are exposed to man-made radiation obtained from nuclear installations, nuclear explosions, nuclear fuel cycle, radioactive waste releases from nuclear reactor operations, and accidents and other industrial, medical, and agricultural uses of radioisotopes.
The most significant sources of exposure, which gives the largest contribution to the public is from medical diagnostic X-rays, nuclear medicine, and nuclear therapy. This is also generated from consumer products such as combustible fluids gas and coal , TV, luminous watches and dials, and electron tubes.
The public are exposed to the radiation from the nuclear fuel cycle, which includes the entire sequence from mining and milling of uranium, the actual production of power at a nuclear power plant, and residual fallout from nuclear weapon testing and accident.
The public are not exposed to all the sources of radiation, for example, patients who are treated with the medical irradiation or the workers of nuclear industry may receive higher radiation exposure than the public [ 19 ]. The sources of radiation exposure in the United States were given in Figure 1. Sources of radiation exposure in the United States. The applications of radioisotopes have played a significant role in improving the quality of life of human beings.
The whole world is aware of the benefits of the radiation, but the phobia of nuclear weapons on Hiroshima and Nagasaki August 6 and 9, and the nuclear accidents occurred in Chernobyl in Russia April 25—26, and Fukushima in Japan March was so deep in the mind of the common man that we can still struggle to come out of it. Major problems arrived by workers in nuclear fields are due to lack of legalization, shortage of resources, and knowledge about nuclear society and safe guards.
Radiotracers are widely used in medicine, agriculture, industry, and fundamental research. Radiotracer is a radioactive isotope; it adds to nonradioactive element or compound to study the dynamical behavior of various physical, chemical, and biological changes of system to be traced by the radiation that it emits.
The tracer principle was introduced by George de Hevesy in for which he was awarded the Nobel prize. The sustainability of radioisotope production is one of the critical areas that receive great attention. There are more than different radioisotopes that are used regularly in different fields; these isotopes are produced either in a medium or in high-flux research reactors or particle accelerators low or medium energy [ 21 ].
Some of the radioisotopes produced by the reactor and particle accelerators and their applications are given in Table 4. Some of the radioisotopes produced by the reactor and particle accelerators and their applications. Nowadays radiotracer has become an indispensable and sophisticated diagnostic tool in medicine and radiotherapy purposes.
The most common radioactivity isotope used in radioactive tracer is technetium 99 Tc. Tumors in the brain are located by injecting intravenously 99 Tc and then scanning the head with suitable scanners. Kidney function is also studied using compound containing I.
Tritium 3 H is frequently used as a tracer in biochemical studies. A most recent development is positron emission tomography PET , which is a more precise and accurate technique for locating tumors in the body. A positron emitting radionuclide e. This technique is also used in cardiac and brain imaging. Compound X-ray tomography or CT scans. The radioactive tracer produces gamma rays or single photons that a gamma camera detects. Emissions come from different angles, and a computer uses them to produce an image.
CT scan targets specific area of the body, like the neck or chest, or a specific organ, like the thyroid [ 22 ]. The most common therapeutic use of radioisotopes is 60 Co, used in treatment of cancer.
Sometimes wires or sealed needles containing radioactive isotope such as Ir or I are directly placed into the cancerous tissue. When the treatment is complete, these are removed. This technique is frequently used to treat mouth, breast, lung, and uterine cancer.
They are used to measure engine wear, analyze the geological formation around oil wells, and much more. Radioisotopes have revolutionized medical practice see Appendix M , where they are used extensively. Over 10 million nuclear medicine procedures and more than million nuclear medicine tests are performed annually in the United States.
Damaged tissues in the heart, liver, and lungs absorb certain compounds of technetium preferentially. Thallium Figure 1 becomes concentrated in healthy heart tissue, so the two isotopes, Tc and Tl, are used together to study heart tissue.
Iodine concentrates in the thyroid gland, the liver, and some parts of the brain. Salt solutions containing compounds of sodium are injected into the bloodstream to help locate obstructions to the flow of blood. Radioisotopes used in medicine typically have short half-lives—for example, the ubiquitous Tcm has a half-life of 6. This makes Tcm essentially impossible to store and prohibitively expensive to transport, so it is made on-site instead. Hospitals and other medical facilities use Mo which is primarily extracted from U fission products to generate Tc These two water-soluble ions are separated by column chromatography, with the higher charge molybdate ion adsorbing onto the alumina in the column, and the lower charge pertechnetate ion passing through the column in the solution.
A few micrograms of Mo can produce enough Tc to perform as many as 10, tests. Radioisotopes can also be used, typically in higher doses than as a tracer, as treatment. Radioisotope Half-life Use Phosphorus Yttrium 64 hours Used for liver cancer therapy. Molybdenum Iodine 8. Samarium Lutetium 6. Used to treat a variety of cancers, including neuroendocrine tumours and prostate cancer. Radioisotope Half-life Use Carbon Also used to detect heart problems and diagnose certain types of cancer.
Nitrogen 9. Oxygen 2. Fluorine 1. Used in a variety of research and diagnostic applications, including the labelling of glucose as fluorodeoxyglucose to detect brain tumours via increased glucose metabolism. Copper Gallium Iodine Thallium Used to predict the behaviour of heavy metal components in effluents from mining waste water. Used in gamma radiography, gauging, and commercial medical equipment sterilisation. Used to study sewage and liquid waste movements. Used as a radiotracer to identify sources of soil erosion and depositing, and also used for thickness gauging.
Used in gamma radiography. Used to trace sand movement in river beds and on ocean floors, and to trace sand to study coastal erosion. Used to image the brain, thyroid, lungs, liver, spleen, kidney, gall bladder, skeleton, blood pool, bone marrow, heart blood pool, salivary and lacrimal glands, and to detect infection. Currently in clinical trials. Supplied in wire form for use as an internal radiotherapy source for certain cancers, including those of the head and breast.
Used in Positron Emission Tomography PET scans to study brain physiology and pathology, to detect the location of epileptic foci, and in dementia, psychiatry, and neuropharmacology studies. Used in PET scans to label oxygen, carbon dioxide and water in order to measure blood flow, blood volume, and oxygen consumption.
The most widely-used PET radioisotope.
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