Applies of Radioisotopes

7/31/2019 Applies of Radioisotopes

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Medicalradioisotopes://Nuclear medicine uses small amounts o radiation to provide inormation about apersons body and the unctioning o specic organs, ongoing biological processes,or the disease state o a specic illness. In most cases, the inormation is used byphysicians to make an accurate diagnosis o the patients illness. In certain casesradiation can be used to treat diseased organs or tumours.

Nuclearimaging://Nuclear imaging is a technique that uses radioisotopes that emit gamma raysrom within the body. To make a radiopharmaceutical, a radioisotope is attachedto a pharmaceutical that is taken up by a specic organ or specic diseasedtissues. The radiopharmaceutical is given orally, injected or inhaled, and isdetected by a gamma camera which is used to create a computer-enhancedimage that can be viewed by the physician.

There is a signicant dierence between nuclear imaging and other medicalimaging systems such as CT (computerised tomography), MRI (magneticresonance imaging) or X-rays.

Radioisotopes are playing an increasingly important part in Australian lie. They are widely used inmedicine, industry and scientic research, and new applications or their use are constantly beingdeveloped. In many cases, radioisotopes have no substitute and in most o their applications they aremore eective and cheaper than alternative techniques or processes.

Radioisotopes have been used routinely in medicine or over 30 years. On average, every Australiancan expect at some stage in his or her lie to undergo a nuclear medicine procedure that uses aradioisotope or diagnostic or therapeutic purposes. Some radioisotopes used in nuclear medicinehave very short hal-lives, which means they decay quickly; others with longer hal-lives take more

time to decay, which makes them suitable or therapeutic purposes.

Industry uses radioisotopes in a variety o ways to improve productivity and gain inormationthat cannot be obtained in any other way. Radioisotopes are commonly used in industrialradiography, which uses a gamma source to conduct stress testing or check the integrity owelds a common example is to test aeroplane jet engine turbines or structural integrity.Radioisotopes are also used by industry or gauging (to measure levels o liquid insidecontainers, or example) or to measure the thickness o materials.

Radioisotopes are also widely used in scientic research, and are employed in a range oapplications, rom tracing the fow o contaminants in biological systems, to determiningmetabolic processes in small Australian animals.


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:>X-raytechnologyletsdoctorsseestraight throughhumantissuetoexaminebrokenbones,cavities and swallowed objects with extraordinary ease. Modied X-ray procedures can be used to examinesoter tissue, such as lungs, blood vessels or intestines. During an X-ray, a camera records the pattern oX-ray radiation that passes through the patients body. A conventional X-ray image is basically a shadow apiece o lm on the other side o the X-ray source registers the bones silhouette.]]

:>CT,sometimescalledCAT(ComputerisedAxialTomography)scan,uses special X-ray equipmentto obtain image data rom hundreds o dierent angles around, or slices

through, the body. The inormation is then processed to show a 3-D cross-section o body tissues andorgans. Since they provide views o the body slice by slice, CT scans provide much more comprehensiveinormation than conventional X-rays. CT imaging is particularly useul because it can show several types otissue lung, bone, sot tissue and blood vessels with greater clarity than fat X-ray images.]]

:>MRIusesradiowavesandastrongmagneticeld(rather than X-rays) to provide remarkably clear and detailed pictures o internal organs and tissues. Byexciting protons in the body (most abundant in the hydrogen atoms o water), the resulting image shows

dierences in water content and distribution within various tissues. This results in two or three dimensionalmaps o tissue types. MRI can also image blood fow, and provides an unparalleled view inside the body. MRIis a preerred method or the diagnosis o many injuries and conditions because it provides the ability totailor each examination to obtain the specic inormation required.]]


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:>Diagnosticradiopharmaceuticals canbeusedtoexaminebloodfowto the brain, to assess unctioning o the liver, lungs, heart or kidneys, to assess bone damage,and to conrm other diagnostic procedures.]]

:>Neuroblastomaisoneothemostcommon solidmalignantcanceroustumoursochildhood,and most children diagnosed with this cancer are under ve years o age. It can occur anywhere in the body,but most oten occurs in the adrenal glands in the abdomen. Iodine-123 is made in a cyclotron and thenattached to the drug MIBG (meta-iodobenzylguanidine), which is taken up by neuroblastoma cells, aterbeing administred by injection. Attaching a small amount o radioactive iodine to the MIBG enables thetumours to be seen by a radiation scanner, producing high quality images pinpointing the location and size othe tumour. Treatment options include surgery, chemotherapy, and radiotherapy using MIGB.]]


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Diagnosticradiopharmaceuticals://Scientists have identied a number o chemicals that are absorbed by specic body tissues and organs.They are called targeting agents or molecules. The brain, or example, consumes large quantities oglucose. Using similar knowledge, radiopharmacists can choose the appropriate targeting chemical, labelit with an appropriate radioisotope and use it as a radioactive tracer or a particular body tissue, organor unction. Once the substance has been tagged with a radioisotope and introduced into the body, it is

incorporated into the normal biological processes and excreted in the usual ways.

Diagnostic radiopharmaceuticals can be used to examine blood fow to the brain; to assess unctioningo the liver, lungs, heart or kidneys; to assess bone damage; and to conrm other diagnosticprocedures. They are used in sports medicine to diagnose stress ractures, which are not generallyvisible in X-rays.

Radiopharmaceuticals are used in very small quantities or diagnostic work just enough isadministered to obtain the required inormation beore the radiopharmaceutical decays or is excretedrom the body. The radiation dose received is similar to that rom diagnostic X-rays. The non-invasivenature o this technology, together with its ability to reveal organ unction, makes it a powerul

diagnostic tool.The most common radioisotopes used or diagnosis are technetium-99m, distantly ollowed byiodine-123, fuorine-18, thallium-201 and gallium-67.

Therapeuticradiopharmaceuticals://Rapidly dividing cells are particularly sensitive to damage by radiation. For this reason, somecancerous growths can be controlled or eliminated by irradiating the area. This is calledradiotherapy.

With internal radiotherapy, the radioisotope that generates the radiation is localised in theaected organ. This is achieved by administering it as a radioactive element that is taken upby that part o the body, or by attaching the radioactive element to a biological compound,which lodges in the body at the disease site.

Iodine-131 is used or internal radiotherapy, to treat thyroid cancer and hyperthyroidism(an over-active thyroid).


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Externalradiotherapyandbrachytherapy://External radiotherapy is carried out using a radioactive source that is outside the body. The radiationbeam is directed towards the diseased tissue so the beam can deliver a high dose o radiation whilesparing the surrounding healthy tissue.

Brachytherapy uses a source implanted in the body at the site to be irradiated. Brachytherapysources can be placed on the skin or implanted internally, and can be temporary or permanently

let in the patient.

Where the source is internal, various radioisotopes can be used. Iridium-192, or example, isproduced in wire orm and introduced through a catheter to the target area usually in the heador breast. The implant is let in or the required time and then removed to shielded storage. Theprocedure is cheaper than using external radiation and gives less overall radiation to the body.

Prostate cancer brachytherapy is an increasingly popular orm o treatment o prostatecancer. Low dose rate seeds o iodine-125 are implanted into the prostate and permanentlylet in the patient.

Biochemicalanalysis://Biochemical analysis is usually carried out in vitro (out o the body) and is used toquantiy very small amounts o biological substances such as enzymes, hormones,steroids and vitamins in blood, urine, saliva or other body fuids. Radioisotopes areused in these tests because they can be used to label molecules o biological samplesand are easy to detect, even in low concentrations. Known as radioimmunoassays,these procedures are commonly used to help diagnose diseases such as diabetes,thyroid disorders, hypertension and reproductive problems.

Another radiopharmaceutical, incorporating samarium-153 and known commercially as Quadramet,is used internally to reduce the pain rom secondary bone cancers associated with breast, prostateand some other cancers. Quadramet is preerable to traditional pain killers such as morphinebecause it improves the patients quality o lie, allowing them to be more lucid during time spentwith amily.

Considerable research is being conducted worldwide into the use o radioisotopes attachedto highly specic biological compounds. The eventual tagging o these compounds with a

therapeutic dose o radiation may lead to the regression or even cure o some diseases, andmany scientists are enthusiastic about the potential o these radioisotopes.


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>researchreactor-producedmedicalradioisotopes_//

:>Bothreactorandcyclotron-producedradioisotopes areneededtoservicealloAustraliasmedicalneeds.]]

Radioisotope Hal-lie UseChromium-51 27.7 days Used to label red blood cells and quantiy gastro-intestinal protein loss.

Iodine-131 8.02 days Used to diagnose and treat various diseases associated with the human thyroid.

Iridium-192 73.83 daysSupplied in wire orm or use as an internal radiotherapy source or certaincancers, including those o the head and breast.

Molybdenum-99 66 hoursUsed as the parent in a generator to produce technetium-99m, the most widelyused radioisotope in nuclear medicine.

Phosphorus-32 14.28 days Used in the treatment o excess red blood cells.Samarium-153 46.7 hours Used to reduce the pain associated with bony metastases o primary tumours.

Technetium-99m 6.01 hoursUsed 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 inection.

Yttrium-90 64 hours Used or liver cancer therapy.


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Reactorandcyclotron-producedradioisotopes://The great majority o medically useul radioisotopes are made in a nuclear research reactor, however cyclotronsalso produce radioisotopes that complement those manuactured in nuclear research reactors.

The nucleus o an atom contains two types o particles neutrons and protons. Stable atoms have a stableratio o neutrons and protons in the nucleus, while unstable atoms have an unstable ratio. Scientists makeradioactive atoms by adding either extra neutrons or extra protons.

Atoms with extra neutrons in the nucleus are neutron-rich and are produced in a nuclear reactor. Atomswith extra protons in the nucleus are neutron-decient and are produced in a particle accelerator such asa cyclotron. Neutron-rich and neutron-decient radioisotopes decay by dierent means and thus havedierent properties and dierent uses. The end use o the radioisotope determines the radioactive propertiesrequired, and hence whether a nuclear reactor or a cyclotron is used to produce the radioisotope.

Both types o radioisotopes are needed to service all o Australias nuclear medical needs. Over 80%o the radioisotopes actually used in medical procedures worldwide come rom reactors. The mostcommonly used radioisotope, molybdenum-99 (which decays into technetium 99-m) can only beproduced economically in a nuclear research reactor. Also, the emerging generation o therapeutic

isotopes can only be produced in such a reactor.

Industrialradioisotopes://Industry uses radioisotopes in a variety o ways to improve productivity and gain inormation thatcould not otherwise be obtained. Sealed radioactive sources are used in mineral analysis, industrialradiography and gauging applications. Radioisotopes with high gamma ray levels are also used inthe radiation sterilisation o medical supplies and ood packaging.

Gammaradiography://Gamma radiography works in a similar way to the X-ray camera used to scan luggage at airports.A small pellet o radioactive material in a sealed titanium capsule is positioned on one sideo the object being screened. A sheet o photographic lm is placed on the other side. Thegamma rays are beamed rom the radioactive source and pass through the object to createan image on the lm. Just as X-rays show a break in a bone, gamma rays show faws inmetal castings or welded joints. The technique allows critical components to be inspected orinternal deects without damaging the component or making it radioactive.


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low reading

high reading

conveyor

Gamma radiography has several advantages over an X-ray camera. X-ray cameras are large andcumbersome and require a high voltage electrical charge source. Radioactive sources, on the otherhand, are small and do not require power. This means the radioisotopes can be transported easilyto remote areas and used where there is no power. They can also be located inside equipment toproduce photographs o internal joints or components without the need or dismantling.

Gauging://Radioisotope gauging is based on the principle that the radiation emitted rom a radioisotope willbe reduced in intensity by matter located between the radioisotope and a detector. The amount othis reduction can be used to gauge the presence or absence o the material, or even to measurethe quantity o material between the source and the detector. The advantage o this orm ogauging is that there is no contact with the material being measured.

One application is in the manuacturing o plastic lm. The lm runs at high speed betweena radioactive source and a detector and the detector signal strength is used to control thethickness o the plastic lm. A similar technique is used to measure the height o coal in

hoppers eeding power station urnaces.

A variation on this technique is used to measure material coatings. When the intensity oradiation rom a radioisotope is being reduced by matter in the beam, some radiation isscattered back towards the radiation source. Analysis o this back-scattered radiationprovides inormation about the materials coating.

Smokedetectors://In the chamber o smoke detectors with a small americium-241 source, atoms o airare ionised. The electronics in the smoke detector sense the resulting small amount

o electrical current rom the electrical supply. When smoke or steam enters theionisation chamber, it disrupts this current. The smoke detector senses the drop incurrent between the plates and sets o the alarm.

These smoke detectors are installed in a large number o public areas and privatehomes. They are so widespread that they represent the largest number o devicesbased on radioisotopes used world-wide.

^:Levelgaugesorthecontroloacoalhopper://


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>cyclotron-producedmedicalradioisotopes_//

Radioisotope Hal-lie Use

Copper-64 12.7 hoursUsed to study genetic disease aecting copper metabolism; in PositronEmission Tomography; and also has potential therapeutic uses.

Gallium-67 78.25 hours Used in imaging to detect tumours and inections.

Iodine-123 13.2 hours Used in imaging to monitor thyroid unction and detect adrenal dysunction.

Thallium-201 72.9 hours Used in imaging to detect the location o damaged heart muscle.

Carbon-11Nitrogen-13Oxygen-15Fluorine-18

20.3 minutes10 minutes

122 seconds1.83 hours

These are used in Positron Emission Tomography to study brain physiologyand pathology; or detecting the location o epileptic oci; and in dementia, andpsychiatry and neuropharmacology studies. They are also used to detect heartproblems and diagnose certain types o cancer.


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Useinmineralanalysisandprocessing://Radioisotopes are used to analyse the content o mineral samples. Radioisotopes are also usedwidely as gamma sources in the continuous measurement o mineral slurry density, a vitally importantactor in the control o mineral processing and hydrometallurgical operations (the use o liquid toseparate a metal rom its ore).

Gamma ray transmission or scattering can determine the water content o coal on conveyer belts.

The measurements are based on the act that gamma ray interactions vary according to theatomic number o the material being bombarded; atoms in water have a dierent atomic numberto atoms in coal.

Scienticuses://Radioisotopes are used in many areas o research and science. The age o water romunderground bores can be estimated rom the activity o naturally occurring radioisotopesin the water, inorming decisions regarding the use o groundwater or consumption. Open-air nuclear weapons testing in the 1950s and early 1960s nearly doubled the amount ocarbon-14 in the atmosphere. Scientists can use the increased number o carbon-14 atoms

in the environment as tracers to measure soil movement and land degradation. For example,by the amount o carbon-14 in organic material within sediments, scientists can determinei it was deposited in sedimentary layers beore or since this period o weapons testing.

Levels o certain radioisotopes in environmental samples can be measured to checkwhether nations are in compliance with agreements concerning the development onuclear weaponry. Nuclear activities may produce routine or accidental releases oradioactive material into the environment. Iodine-129 and uranium-236 can be measuredin environmental samples, and are signatures o nuclear activities such as reprocessingirradiated nuclear uel.

Radiotracer techniques are oten used to validate mathematical models o sediment and

contaminant transport in the coastal zone and so contribute to sustainable development.

Even minute amounts o radioactive material can be detected easily, which makes itideal or use in tracing the movements o water, gases or even insects. Radioactivetracers mixed with sewage are used to track sewage dispersion. A similar technique isused to trace small leaks in complex systems such as power station heat exchangers.Flow rates o liquids and gases in pipelines can be measured accurately, as can thefow rates o large rivers, all with the assistance o radioisotopes.

radiation detectors

at different levels

ocean outlet

current flow

ocean floor

_^:Tracingosewagedispersionromoceanoutalls_//


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Applies of Radioisotopes