Nuclear medicine

Answering your questions

Nuclear medicine

What is nuclear medicine?This is a branch of medicine that uses radiationfrom radioactive tracers to provide informationabout the function of specific organs. In somecases, radioactivity can be used to treat certainconditions such as an overactive thyroid.

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ANSTO’s OPAL research reactor in Sydney

What is radiation?Radiation is a type of energy, which exists in ourenvironment in many forms and comes from bothnatural and man-made sources. Light that allowsus to see and the warmth we get from the sun orfrom nature are natural forms of radiation.Examples of man-made radiation include themicrowave radiation that is used for cooking andradio waves for communication over long distances.

Ionising radiation comes from both natural andman-made sources. It comes from outer space,the sun, the earth, the air, our food and drink andfrom the buildings we live in. This is the naturalbackground radiation to which everyone isexposed. Each of us receives a small dose ofnaturally occurring radiation on an annual basis.Nuclear medicine studies use ionising radiation, asdo x-ray studies.

Nuclear medicine is extremely safe because theradioactive tracers or radiopharmaceuticalscommonly used are quickly eliminated from thebody through its natural functions. In addition, thetracers used rapidly lose their radioactivity. In mostcases, the dose of radiation necessary for a scan isvery small. For example, a patient having a lungscan is exposed to the same dose of radiation theywould receive from eight return air flights betweenSydney and London.

What is a half-life?Nuclear medicines used for diagnosis or treatmentgenerally have short half-lives. A half-life is thetime it takes for the level of radioactivity to drop tohalf the starting level. Nuclear medicines typicallyhave a half-life of several hours or days. Thismeans they rapidly lose their radioactivity levelwithin the predetermined half-life.

Nuclear medicine–Answering your questions

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Where are radiopharmaceuticalsproduced?Australia is certainly a lucky country in the sensethat it is one of the very few nations in the worldto produce the radioactive tracers necessary fordiagnostic nuclear medicine. In fact, without theability to produce radiopharmaceuticals in Australia,we would have to import them from as far awayas Europe, Canada and South Africa.

Radiopharmaceuticals are manufactured in Sydneyby the Australian Nuclear Science and TechnologyOrganisation (ANSTO) using a cyclotron and itsnuclear research reactor, OPAL.

It is necessary to have both the research reactorand the cyclotron as each produces different typesof radiopharmaceuticals.

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The manufacturing process is regulated by strictquality-control requirements as approved by theAustralian Government.

The radiopharmaceuticals are supplied to nuclearmedicine centres across Australia. Every yearthousands of people are diagnosed and treated atthese centres. Without access to this vitaltechnology, many Australians would be facing areduced quality of medical care.

Australia also exports radiopharmaceuticals to theUnited States, Europe and Asia.

What is the difference betweenradiopharmaceuticals made in a cyclotronand those made in a nuclear reactor?The nucleus of an atom contains two types ofparticles – neutrons and protons. Non-radioactiveatoms have a ‘stable ratio’ of neutrons and protonsin the nucleus, while radioactive atoms have an‘unstable ratio’. Radioactive atoms are made byadding either extra neutrons or extra protons.

Atoms with extra neutrons in the nucleus areneutron-rich; they are produced in a nuclear reactor– this is the great majority of medically usefulradiopharmaceuticals. Atoms with extra protons inthe nucleus are proton-rich and are produced in aparticle accelerator such as a cyclotron - theycomplement those manufactured in nuclear reactors.


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Neutron-rich and proton-rich radioisotopes decayby different means and thus have differentradioactive properties and different medical uses.

Both types of radioisotopes are needed to serviceall of Australia’s nuclear medicine needs. Over 80per cent of the radioisotopes used in medicalprocedures, including the most commonly usedradiopharmaceutical technetium-99, can only beproduced economically in a nuclear research reactor.

When is a nuclear medicine scan needed?There is about a one in two chance of an Australianneeding a nuclear medicine scan during his or herlifetime. Scans using radiopharmaceuticals candiagnose numerous conditions. Scans of the heart,thyroid, lungs and kidney are common. However,by far the majority of scans involve the skeleton.These are usually carried out to diagnose infection,tumour spread, and fractures or sports injuries.

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Should I prepare for a scan?Some scans may require special preparation. Aswith other tests, if you are pregnant or if there isany possibility that you may be pregnant or if youare breastfeeding, you must tell your physician. Itis important that you read all the material given toyou prior to your appointment.

What can I expect when I have a scan?When you undergo a scan, a radiopharmaceuticalwill be given, either by injection into a vein, bymouth or through a breathing device. Theradiopharmaceutical will concentrate in theparticular part of your body under investigation.

Sometimes you may have to wait for a few hoursor even a day or two after the radiopharmaceuticalhas been administered for the scan to be done.This is because it may take a while for theradiopharmaceutical to lodge in the part of yourbody to be examined.

The radiopharmaceutical continuously gives offinvisible radiation, known as gamma rays. Theimages are stored digitally on computer for reportingby doctors who will be able to tell if the part ofyour body being tested is functioning normally.


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Are there different types of scans? Yes, there is gamma camera imaging and positronemission tomography (PET) imaging.

Gamma imaging operates in two different modes,PLANAR imaging and single photon emissioncomputed tomography (SPECT) imaging.

If your doctor refers you for a nuclear medicine scan,one or more of the following methods may be used:

PLANAR imaging

PLANAR is the most common of the three methods. Itinvolves the injection into the body of a small amountof a chemical substance tagged with a radioactivetracer. Depending on the chemical substance used,the radiopharmaceutical concentrates in the part ofthe body being investigated, for example theskeleton, lungs, heart or liver, and gives off gammarays. A gamma camera produces a two-dimensionalimage of the radioactivity occurring in that organ.

SPECT imaging

SPECT is also widely used and the process ofinjecting a radioactive tracer is the same as thePLANAR technique. Instead of being stationary,the gamma camera moves around the bodyproviding a series of images. This takes about 20-30 minutes. SPECT and PLANAR imaging arehighly convenient technologies as they useradiopharmaceuticals, which can be easily distributed,stored and mixed ready for use at nuclear medicineclinics and hospitals across Australia.

PET imaging

PET is a very similar technique to SPECT but usesdifferent radiopharmaceuticals. Theradiopharmaceuticals required for PET have veryshort half-lives and are produced by a cyclotron.The most common radiopharmaceutical used isradioactive sugar. PET studies require you to lie

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quietly for up to one hour after the injection so thatthe radiopharmaceutical localises correctly ratherthan going to your muscles.

Will I have to stay in hospital?Patients having a diagnostic scan will often beasked to stay in the nuclear medicine departmentfor a few hours, although in some cases patientsare asked to return for a number of visits or to stayin hospital for a short period.

If you are undergoing therapy, particularly for anoveractive thyroid gland, you will probably betreated as an outpatient and will not need to stayin hospital. If you do need to stay for certain typesof therapy, then you will usually only be in hospitalfor two or three days. This is not because of anyrisk to your health but because doctors want toensure that radioactive materials are dealt withsafely when they are excreted from your body.

What does nuclear medicine treatmentinvolve?By far the widest application of nuclear medicine isfor diagnosis. However, there are a number ofoccasions when radioactive materials are used totreat certain conditions, particularly cancer. This isknown as therapy.

Nuclear medicine therapy usually involves takingradiopharmaceuticals orally (either in capsule or liquidform) and the most common conditions treated inthis way are overactive thyroids and thyroid cancer.Radiopharmaceuticals are also injected into the body,usually the joints, to treat certain types of arthritis.Newer treatments involve the intravenous injectionof radiopharmaceuticals for the relief of pain fromtumours that have spread to bone. In Australia manypatients are treated with radiopharmaceuticals thathave a medical effect on their bodies. For most, onedose is all that is required.


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Are there any side effects?Side effects are extremely rare for diagnosticscans. When radiation or radiopharmaceuticals areused in therapy, there are sometimes minor sideeffects. These will be explained to you by thenuclear medicine staff together with measures toreduce or avoid the symptoms.

Who carries out nuclear medicineprocedures?If your doctor recommends you have a scan ornuclear medicine treatment, you will be placed inthe care of a team of specially trainedprofessionals. Physicians, technologists,pharmacists and nurses will ensure that youreceive a high level of care and that your doctor isprovided with accurate reports on your condition.

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What happens after a scan or therapy?The specially trained physicians will report on thescan’s appearance and send the results to yourdoctor to evaluate, together with those of any other tests you may have had. In the majority of cases, you will be able to continue your dailyactivities as usual.

What are the benefits of nuclear medicine?Nuclear medicine enables doctors to produce aquick and accurate diagnosis for a wide range ofconditions and diseases at any age. In turn, thisallows the appropriate treatment to begin as earlyas possible, which gives a far greater chance ofbeing fully effective. In addition, the tests arepainless and most scans expose patients to only a minimum amount of radiation. It is a very accurate way to examine whether some tissues are functioning properly.

Therapy using nuclear medicine is an effective, safeand relatively inexpensive way of controlling and insome cases, eliminating certain conditions such asan overactive thyroid, thyroid cancer and certaintypes of arthritis. Nuclear medicine is a vital part ofhealthcare as it gives many people the opportunityof continuing to live full and healthy lives.

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Produced by ARI in cooperation with the Australia andNew Zealand Society of Nuclear Medicine (ANZSNM) andthe Australia and New Zealand Association of Physiciansin Nuclear Medicine (ANZAPNM).

ANSTO Radiopharmaceuticals (ARI) is a subsidiaryof the Australian Nuclear Science and TechnologyOrganisation (ANSTO) which is Australia’s centreof nuclear expertise specialising in the applicationsof nuclear science.

ANSTO is based at Lucas Heights in southernSydney; it is a publicly owned organisationoverseen by the Federal Government.

Members of the public are welcome to visitANSTO for organised tours.

If you wish to find out more about tours, tounderstand how nuclear science improves the livesof Australians, or to obtain further information,please call ANSTO on (02) 9717 3111.

For further information, please contact the nuclearmedicine department at your nearest hospital.

Nuclear medicine, answering your questions

Updated May 2008. Printed May 2008