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You must have heard of diagnostic procedures that allow physicians to explore the parts and organs of the body with minimum invasion and also be able to view the organ functions in vivo. If you are wondering what are radioactive isotopes and their use in nuclear medicine, this article will help clear the doubts in your minds. Know more on radioactivity.

Radioactive Isotopes
Isotopes are a two or more types of a chemical element and have the same atomic number and position in the periodic table. They share similar chemical behavior but have different atomic mass and physical properties. All chemical elements have one or two isotopes. Radioactive isotopes are those isotopes that have an unstable number of protons and neutrons. This instability is created by the neutron activation wherein, a neutron captured in the nucleus of an atom leads to an excess of neutron rich nucleus. Cyclotrons are used to manufacture proton rich radioactive isotopes. The nucleus of a radioactive isotope emits particles like alpha, beta or positron and photons like gamma rays, to achieve energetic stability during a radioactive decay.

What is Nuclear Medicine
Nuclear medicine is the branch of science under medicine, that uses radiation to give information regarding the functioning of a specific organ in the human body or to treat a disease. This collected information gives accurate and immediate diagnosis of the patient's illness. Radioactive isotopes in medicine are used to form images of the thyroid, bones, heart, liver and many other organs. Radioactive isotopes used in medicine have also helped in treating diseased organs and tumors. Know more on cancer treatment: radiation therapy.

The most commonly used radioactive isotope in medicine all over the world is technetium-99, that accounts for 80% of nuclear medicine procedures. In the US alone, over 18 million nuclear medicine procedures are recorded per year.

In 1930s, scientists used radioactive isotope to measure the dose of administered radioactive iodine required when localized in the thyroid. A Geiger counter was used to evaluate the radiation emitted from the neck and make further diagnosis. This use of iodine radioactive isotopes in medicine was merely speculative. The real breakthrough came with the invention of gamma scintillation camera in the 1950s, by Hal Anger, an American engineer. This camera helped make the use of radioactive isotopes in medicine, in diagnosing and treatment of possible illness.

The first radioactive isotopes used in medicine were a tool to diagnose, detect and treat thyroid disorders and goiter treatment. There was an extensive research conducted in the field of nuclear medicine, that lead to many discoveries and invention of ultra sharp diagnostic methods and imaging systems. There are 5 Nobel prizes awarded for various discoveries and inventions in nuclear medicine. The Positron Emission Tomography or the PET scan was the first diagnostic tool invented by Peter Alfred Wolf that used radioactive isotopes in medicine. This invention was followed by CT scan (computerized tomography) and then MRI (magnetic resonance imaging). Let us have an overview of the various uses of radioactive isotopes in medicine. Know more on CT scan with contrast.

Radioactive Isotopes Used in Medicine for Diagnostic Techniques
Most of the diagnostic techniques use radioactive tracers that emit gamma rays from within the body. These are short-lived tracers that are linked to chemical compounds, that help in scrutinizing specific physiological processes. The mode of administering these tracers is by injections, inhalation or orally. Single photons are detected by a gamma camera, that gives view of organs from different angles. The image is build up by the camera from the point through which the radiation is emitted. A computer helps enhancing the image that is viewed by the physician on a screen and helps him detect any abnormality in the organ.

In a PET scan, a positron-emitting radionuclide is introduced by an injection, that is accumulated in the target tissue. With the decay of the radionuclide, the emitted positrons that combine with the nearby electron, result in the emission of gamma rays that are easily identifiable, traveling in opposite direction. A PET camera detects these rays and gives a precise indication of their origin. The most common role of PET scan radioactive isotopes in medicine is fluorine-18, that is used as a tracer in oncology. It is the most effective non-invasive method to detect and evaluate cancers. This method is also used for cardiac and brain imaging.

PET and CT scans have been combined to make a new procedure that provides 30% better diagnosis. It helps provide important information on diseases, varying from dementia to cardiovascular and even cancer. The use of radioactive isotopes in medicine helps detect the position and concentration of radioactive isotopes in the body. This helps detect organ malfunction if the isotope is taken up partially by the organ known as 'cold spot' or in excess called as 'hot spot'. When a series of images are taken over a time period, it helps in detecting organ malfunction by the unusual pattern or rate of isotope movement.

Radioactive Isotopes Used in Medicine for Radionuclide Therapy (RNT)
The use of radioactive isotopes in medicine involves radionuclide therapy. Cancerous cells can be controlled or even eliminated by irradiating the tumor growth region. Teletherapy, also known as external irradiation is carried out by gamma beam emitted from radioactive cobalt-60 source. In many developed countries, the use of versatile linear accelerators is being utilized.

Internal radionuclide therapy involves administering small radiation source like a gamma or beta emitter in the target area. Brachytherapy or short range therapy mainly uses Iodine-131 to treat thyroid cancer. It also helps treat non-malignant thyroid disorders. In case of brain cancer or breast cancer, Iridium-192 is preferred. These isotopes are produced in a wire form, that are introduced through a catheter into the target area. The implantation wire is removed once the appropriate dose has been administered. Advantage of brachytherapy is that it is more target specific, less exposure of radiation to the body and is cost effective. Know more on breast cancer radiation side effects.

Lethal dose of radiation is given to the patient to kill all the defective bone marrow cells, before replacement with healthy bone marrow cells, in case of treatment of leukemia. Stronium-89 and samarium 153 are used to provide relief to pain induced by cancer. The new radioactive isotope being used for pain therapy is rhenium-186.

To control dispersed cancers, Targeted Alpha Therapy (TAT) is begin used. In this, a short range of highly energetic, alpha emissions are allowed to enter the targeted cancer cells after a carrier has taken the alpha-emitting radionuclide to the target area. There are positive results from laboratory studies, that have lead a way for clinical trials for diseases like leukemia, cystic glioma and melanoma.

Radioactive Isotopes Used in Medicine for Biochemical Analysis
Radioactive isotopes can be easily detected even if they are present in low concentration. This has helped in the use of radioactive isotopes in medicine, for labeling molecules of biological samples in vitro. There are many tests that help detect the constituents of blood, serum, urine, hormones, antigens and drugs by linking them with radioactive isotopes. This type of tests are called as radioimmuni-assays.

Radioactive Isotopes Used in Medicine for Diagnostic Radiopharmaceuticals
All organs in the body act differently chemically due to the presence of specific chemicals absorbed by the organ. This knowledge has helped develop diagnostic radiopharmaceuticals, to help examine the blood flow to the brain, functioning of the heart, lungs, liver functions, kidneys, excess growth of bones, etc. it also helps in predicting the effects of surgery and assess changes since the start of treatment. This non-invasive technology helps in observing the organ functions and diagnosing abnormalities without the patient experiencing any form of discomfort. The most widely used radioactive isotope is technetium-99m, that has the ability to disappear without a trace after completion of the test, in a short time. Thallium-201 chloride or technetium-99, is used in Myocardial Perfusion Imaging for detection and prognosis of coronary artery diseases.

Radioactive Isotopes Used in Medicine for Therapeutic Radiopharmaceuticals
Radiation has the ability to weaken or destroy malfunctioning cells under certain medical conditions. A radioactive element that can generate radiation is localized on the target organ with the help of its usual biological path or attaching an element to a suitable biological compound. Beta-radiation is the most commonly used radiation to destroy damaged cells. This is known as radionuclide therapy (RNT) or in simple words, radiotherapy. Iodine-131 is used to treat abnormal conditions like hyperthyroidism. Phosphorus-32 is used to control a disease called 'Polycythemia vera', where an excess of red blood cells are produced by the bone marrow. An extensive research is being carried out all over the world, to find new ways to incorporate the use of radionuclides in curing many more diseases. Know more on chemotherapy and medical tests and tools.

There are many radioactive isotopes that are made in nuclear reactors and some in cyclotrons. Neutron rich radioactive isotopes that are produced through nuclear fission are made in nuclear reactors. Proton-rich radioactive isotopes in medicine are produced in cyclotrons. There are many factors that govern the selection of a radioactive isotope in medicine. The dosage and half-life requires study of many factors. The use of radioactive isotopes in medicine is increasing day by day with accurate results. It also helps in early diagnosis and is a mode of treatment for patients, especially, for those suffering from cancer and tumors. Before undergoing a radiotherapy, make sure you speak to your physician regarding all the matters related to the therapy. Till date, the use of radioactive isotopes in medicine have proved to be very helpful and favorable for innumerable patients, with a positive outcome.