One such radiopharmaceutical is technetium (tcm), the most widely-used radioisotope in nuclear medicine which decays from its parent radioisotope. produced radioisotopes (so other countries don’t all of the short-lived radioisotopes used in nuclear the reactor shutdown noting: “ANSTO’s radioisotope. Title: Radioisotopes (Australian Nuclear Science and Technology Organisation, ANSTO), Author: John A. Shanahan, Name: Radioisotopes (Australian Nuclear.
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The attributes of naturally decaying atoms, known as radioisotopes, give rise to several applications across many aspects of modern day life see also information paper on The Many Uses of Nuclear Technology.
There is widespread awareness of the use of radiation and radioisotopes in medicine, particularly for diagnosis identification and therapy treatment of various medical conditions. In developed countries a quarter of the world population about one person in 50 uses diagnostic nuclear medicine each year, and the frequency of therapy with radioisotopes is about one-tenth of this. Nuclear medicine uses radiation to provide information about the functioning of a person’s specific organs, or to treat disease.
In most cases, the information is used by physicians to make a quick diagnosis of the patient’s illness. The thyroid, bones, heart, liver, and many other organs can be easily imaged, and disorders in their function revealed. In some cases radiation can be used to treat diseased organs, or tumours.
Five Nobel Laureates have been closely involved with the use of radioactive tracers in medicine. In the USA there are over 20 million nuclear medicine procedures per year, and in Europe about 10 million. In Australia there are aboutper year,of these using reactor isotopes. Nuclear medicine was developed in the s by physicians with an endocrine emphasis, initially using iodine to diagnose and then treat thyroid disease. However, the main radioisotopes such as Tcm cannot effectively be produced without reactors.
Radioisotopes are an essential part of medical diagnostic procedures.
Radioisotopes | What are Radioisotopes? | ANSTO
In combination with imaging devices which register the gamma rays emitted from within, they can study the dynamic processes taking place in various parts of the body.
In using radiopharmaceuticals for diagnosis, a radioactive dose is given to the patient and the activity in the organ can then be studied either as a two dimensional picture or, using tomography, as a three dimensional picture. Diagnostic techniques in nuclear medicine use radioactive tracers which emit gamma rays from within the body. These tracers are generally short-lived isotopes linked to chemical compounds which permit specific physiological processes to be scrutinised.
They can be given by injection, inhalation, or orally. The earliest technique developed uses single photons detected by a gamma camera which can view organs from many different angles.
The camera builds up an image from the points from which radiation is emitted; this image is enhanced by a computer and viewed on a monitor for indications of abnormal conditions. Single photon emission computerised tomography SPECT is the current major scanning technology to diagnose and monitor a wide range of medical conditions.
A more recent development is positron emission tomography PET which is a more precise and sophisticated technique using isotopes produced in a cyclotron. A positron-emitting radionuclide is introduced, usually by injection, and accumulates in the target tissue.
As it decays it emits a positron, which promptly combines with a nearby electron resulting in the simultaneous emission of two identifiable gamma rays in opposite directions. These are detected by a PET camera and give very precise indications of their origin. PET’s most important clinical role is in oncology, with fluorine as the tracer, since it has proven to be the most accurate non-invasive method of detecting and evaluating most cancers.
It is also well used in cardiac and brain imaging. It is a very powerful and significant tool which provides unique information on a wide variety of diseases from dementia to cardiovascular disease and cancer. Positioning of the radiation source within rather than external to the body is the fundamental difference between nuclear medicine imaging and other imaging techniques such as X-rays.
Gamma imaging by either method described provides a view of the position and concentration of the radioisotope within the body. Organ malfunction can be indicated if the isotope is either partially taken up in the organ cold spotor taken up in excess hot spot. If a series of images is taken over a period of time, an unusual pattern or rate of isotope movement could indicate malfunction in the organ.
What are radioisotopes?
A distinct advantage of nuclear imaging over X-ray techniques is that both bone and soft tissue radioisoyopes be imaged very successfully. This has led to its common use in developed countries where the probability of anyone having such a test is about one in two and rising. Every organ in our bodies acts differently from a chemical asnto of view. Doctors and chemists have identified a number of chemicals which are absorbed by specific organs.
The thyroid, for example, takes up iodine, whilst the brain consumes quantities of glucose. With this knowledge, radiopharmacists are able to attach various radioisotopes to biologically active substances. Once a radioactive form of one of these substances enters the body, it is incorporated into the normal biological processes and excreted in the usual ways. Diagnostic radiopharmaceuticals can be used to examine blood flow to the brain, functioning of the liver, lungs, heart, or kidneys, to assess bone growth, and to confirm other diagnostic procedures.
Another important use is to predict the effects of surgery and assess changes since treatment. The amount of the radiopharmaceutical given to a patient is just sufficient to obtain the required information before its decay.
The radiation dose received is medically insignificant. The patient experiences no discomfort during the test and after a short time there is no trace that the test was ever done. The non-invasive nature of this technology, together with the ability to observe an organ functioning from outside the body, makes this technique a powerful diagnostic tool.
A radioisotope used for diagnosis must emit gamma rays of sufficient energy to escape from radioisotlpes body and it must have a half-life short enough for it to decay away soon after imaging is completed.
It is radioistoopes isotope of the artificially-produced element technetium and it has almost ideal characteristics for a nuclear medicine scan, such as with SPECT.
Its logistics also favour its use. Technetium generators — a lead pot enclosing a glass tube containing the radioisotope — are supplied to hospitals from the nuclear reactor where the isotopes are made.
They contain molybdenum Mowith a half-life of 66 hours, which progressively decays to Tc The Tc is washed out of the lead pot by saline solution when it is required.
After two weeks or less the generator is returned for recharging. A similar generator system is used to produce rubidium for PET imaging from strontium — which has a half-life of 25 days.
Myocardial perfusion imaging MPI uses thallium chloride or Tc and is important for detection and prognosis of coronary artery disease. The FDG is readily incorporated into the cell without being broken down, and is a good indicator of cell metabolism.
The uses of radioisotopes in therapy are comparatively few, but nevertheless important.
Cancerous growths are sensitive to damage by radiation. For this reason, some cancerous growths can be controlled or eliminated by irradiating the area containing the growth.
External irradiation sometimes called teletherapy can be carried out using a gamma beam from a radioactive cobalt source, though in developed countries the much more versatile linear accelerators are now being used as high-energy X-ray sources gamma and X-rays are much the same. An external radiation procedure is known as gamma knife radiosurgery, and involves focusing gamma radiation from sources of Co on a precise area of the brain with a cancerous tumour.
Worldwide, over 30, patients are treated annually, generally as outpatients. Teletherapy is effective in the ablation of tumours rather than their removal; it is not finely tuned. Internal radionuclide therapy is administered by planting a small radiation source, usually a gamma or beta emitter, in the target area. Short-range radiotherapy is known as brachytherapy, and this is becoming the main means of treatment. Iodine is commonly used to treat thyroid cancer, probably the most successful kind of cancer treatment.
It is also used to treat non-malignant thyroid disorders. Iridium implants are used especially in the head and breast.
They are produced in wire form and are introduced through a catheter to the target area. After administering the correct dose, the implant wire is removed to shielded storage. Permanent implant seeds 40 to of iodine or palladium are used in brachytherapy for early stage prostate cancer. Alternatively, needles with more-radioactive Ir may be inserted for up to 15 minutes, two or three times. Brachytherapy procedures give less overall radiation to the body, are more localized to the target tumour, and are cost-effective.
Treating leukaemia may involve a bone marrow transplant, in which case the defective bone marrow will first be killed off with a massive and otherwise lethal dose of radiation before being replaced with healthy bone marrow from a donor. Many therapeutic procedures are palliative, usually to relieve pain. For instance, strontium and increasingly samarium are used for the relief of cancer-induced bone pain. Rhenium is a newer product for this. Lutetium dotatate or octreotate is used to treat tumours such as neuroendocrine ones, and is effective where other treatments fail.
A series of four treatments delivers 32 GBq. After about four to six hours, the exposure rate of the patient has fallen to less than 25 microsieverts per hour at one metre and the patients can be discharged from hospital. Lu is essentially a low-energy beta-emitter with some gamma and the carrier attaches to the surface of the tumour. A new field is targeted alpha therapy TAT or alpha radioimmunotherapy, especially for the control of dispersed metastatic cancers.
The short range of very energetic alpha emissions in tissue means that a large fraction of that radiative energy goes into the targeted cancer cells, once a carrier such as a monoclonal antibody has taken the alpha-emitting radionuclide such as bismuth to the areas of concern.
Clinical trials for leukaemia, cystic glioma, and melanoma are underway. TAT using lead is increasingly important for treating pancreatic, ovarian, and melanoma cancers. An experimental development of this is boron neutron capture therapy using boron which concentrates in malignant brain tumours. The patient is then irradiated with thermal neutrons which are strongly absorbed by the boron, producing high-energy alpha particles which kill the cancer.
This requires the patient to be brought to a nuclear reactor, rather than the radioisotopes being taken to the patient. Radionuclide therapy has progressively become more successful in treating persistent disease and doing so with low toxic side-effects. With any therapeutic procedure the aim is to confine the radiation to well-defined target volumes of the patient. The doses per therapeutic procedure are typically Gy. Treatment may involve significant radioactivity e. According to US regulatory guidelines for I, the patient can be released if the activity is below 1.
Meanwhile a lot of I is flushed down the hospital toilet and plumbing needs to be shielded accordingly. For some medical conditions, it is useful to destroy or weaken malfunctioning cells using radiation.
The radioisotope that generates the radiation can be localised in the required organ in the same way it is used for diagnosis — through a radioactive element following its usual biological path, or through the element being attached to a suitable biological compound.
In most cases, it is beta radiation which causes the destruction of the damaged cells.
This is radionuclide therapy RNT or radiotherapy. Although radiotherapy is less common than diagnostic use of radioactive material in medicine, it is nevertheless widespread, important, and growing.
An ideal therapeutic radioisotope is a strong beta emitter with just enough gamma to enable imaging tadioisotopes.