From then on until today, there have been rapid expansions in nuclear medicine techniques. We can now study cancer and other diseases with better technology, and by using radioactive sugars and drugs.
Radioisotopes can be produced in two ways – by a reactor, or by a cyclotron. A cyclotron is a machine that can produce new elements by bombarding elements with particles to create new elements, while daughter elements left over from nuclear reactions can also be used for nuclear medicine when appropriate. It is argued that only with a nuclear reactor in Australia in the future, nuclear medicine can grow and develop. Currently, most radioisotopes used in Australia are created by cyclatron.
Detecting diseases and understanding the body
Nuclear imaging examines the chemical reactions that occur in the body, monitor body functions and understand how the body works, also known as diagnostic radiology. When these chemical reactions are irregular, diseases can be easily detected. These diseases can range from anything from heart diseases, thyroid problems, Alzheimer’s and cancer.
To detect problems in the body, doctors use radio-pharmaceuticals or radioactive drugs. These radioisotopes have short half lives which decay to stable material in minutes, hours or days to allow to the patient to be released from hospital in a relatively short time.
To produce such an image, a patient is given, by mouth or injection, a very small amount of a radioactive substance that chemically is drawn to different organs, bones or tissues around the body. Many organs that are not visible by other radiographic techniques become visible by using radioactive substances, which are opaque to radiation. Once the substance reaches its destination it produces an emission that is transformed into a visible image. There are two ways of doing this – in vivo, or within the patient’s body, or in vitro, analysing blood in a laboratory. Because this process uses only trace amounts of radioactivity that decays rapidly in the body – and therefore has a relatively short half-life, this detection process poses practically no danger to the patient. The amount of radiation received in a procedure like this is about the same as what is received when you have a chest x-ray.
The emissions that are given off can be identified by a number of scanners or detectors. One of these is Positron Emission Topography, or PET. It uses positron decay patterns to trace the radioactive material that has been introduces into the body. It can produce high energy 3d images that can measure and determine the structure or function of a specific organ, tumour or other metabolically active site.
How PET works-
Radioisotopes used with PETs decay by positron emission. The emitted positron in the body, when coming into contact with an electron, turn into two gamma rays which easily escape from the human body and are detected. These rays are detected, and when they interact with scintillation crystals, they are converted into light photons, which are converted into electronic signals, and then to an image.
The gamma camera, created by Hal O Anger is another form of detecting radioactive materials introduced to the body. It detects gamma radiation emitted from sources in the body and displays an image that can enable physicians to detect blockages or other dysfunctional activity, particularly in the brain.
Treating diseases with nuclear technology
Treating diseases with nuclear technology, or therapeutic radiation is known to be pain free, safer and more cost effective that other treatments like surgery, and is used to treat a variety of diseases and relieve symptoms. For example therapy with a form of radioactive iodine can treat some thyroid problems, and radiation therapy is used to treat cancer patients.
There are three distinct methods used to treat diseases with radioisotopes – teletherapy, or external beam therapy, brachytherapy and chemotherapy.
Teletherapy involves large doses of radiation to destroy diseased tissues. The treatment involves ionising radiation to kill cells and can be used alone, or in conjunction with hyperthermia – induced fever, or drugs. Alpha radiation is often used to do so, for its high ionising ability, and also because its killing range is only a few cell diameters long. Because of its low penetrating ability, few healthy cells and organs are harmed. Gamma radiation can also be used to kill cancerous cells. Cobalt-60 is one radioisotope used by a teletherapy unit to destroy malignant tumours with high energy gamma rays. The most effective way to kill the tumour is to use several low dose beams of radiation to irradiate the tumour from different directions and thus give the tumour the maximum dose possible while only exposing surrounding cells to low doses of radiation.
Another type of treatment is called brachytherapy destroys cells by placing a radioisotope directly into the tumour, either by a manual implant or by using a device called a remote after loader. A small wire containing radioactive material is inserted into the tumour.
Another form of treating cancers with radioisotopes is by chemotherapy. A radioisotope known to be attracted to the cancerous organ is used in a radioactive medicine, or radiopharmaceutical, and is usually swallowed to treat the cancerous area..
Radioisotopes such as iodine-131 are utilised to treat cancers through radio immunotherapy, or RIT. RIT uses antibodies to guide radiation directly to cancer sources in the body. The materials used in radiotherapy literally seek and destroy cancer cells, and are also called ‘magic bullets’ or ‘smart bombs’.
Radiation therapy is based on the fact that normal tissues have a greater ability to recover from the effects of radiation than tumour cells do. A radiation dose that will destroy tumour cells will only temporarily injure adjacent normal cells.
Superficial radiation is less than 120 kilovolts and is used to treat the skin, eye and other surface cancers. Mega voltage therapy on the other hand is greater than 1000 kilovolts and used to treat tumours deep within the body.
Intense radiation exposure that is used in teletherapy, brachytherapy and all forms of radiotherapy can have side effects such as hair loss, reduced white blood cell count and nausea.
Sometimes, tumour cells are called radioresistant, in other words they are more resistant to radiation than the normal cells surrounding it. In that case, radiation therapy should not be used.
The use of nuclear technology in medicine continues to grow and develop. Researchers are currently working on new applications including the use of radioactive material to clear scarred arteries after heart surgery and to treat arthritis. Medical research using radioisotopes also are being developed to fight diseases such as Huntington’s and Alzheimer’s disease. Hopefully new developments in nuclear medicine will enable us to not only know more about the human body, but also to be able to detect and treat cancers and other diseases in the future.
