June 18, 2009
The shut down of the Chalk River nuclear reactor in Ontario has hospitals across the country (and around the world) scrambling over a severe shortage of medical supplies. Many medical exams and treatments have been delayed or cancelled as a result. Many of us associate exposure to high doses of radioactive radiation with deformities - think of the results of Hiroshima or Chernobyl — so a likely question is what do atomic bombs have to do with medical tests? The answer is nuclear isotopes!
All matters are made of billions of atoms of elements listed in the Periodic Table
. At the center of each atom is a nucleus formed from protons and neutrons. These particles weigh the same, but protons carry a positive charge while neutrons are not charged. The number of protons a nucleus has defines the element to which the nucleus belongs while the number of neutrons may vary (e.g., oxygen atoms have 16 protons in their nuclei (plural of nucleus), while gold atoms that have 79 protons in their nuclei).
Like charges repel each other, so each nucleus contains about the same number of neutrons between neighbouring protons so that the atom as a whole stays stable. Some atoms hold more or less neutrons than protons, and these variations are known as "isotopes" of the same element. As a result, there is energy held within the nucleus, and when this energy exceeds a stable level, the atom will break apart, or more technically, undergo radioactive decay. Any atom that can undergo a radioactive decay is known as a radionuclide.
Did you know? There are three types of radioactive decay: alpha decay, beta decay, and gamma decay.
In nuclear weapons, atoms with extremely unstable nuclei (usually man-made) are used. When trillions of atoms all give off this energy at once, which is what happens when a weapon is triggered, an explosion occurs.
In medicine, radioisotopes are used for diagnosis, treatment, and research. In diagnosis, for example, radioactive chemicals (an entirely different type than those used in a nuclear weapon, and is not harmful to the patient when used in low, approved doses) are injected in to patients' blood stream and gamma rays are emitted from within the body. With special detectors, gamma rays can be detected and the information can be seen on a computer screen in order to provide diagnostic information about a person's internal anatomy and the functioning of specific organs. After the test, the patient will not stay radioactive forever, of course. The chemicals injected will be excreted from the body along with urine.
Did you know? A frequently used radionuclide in medicine is iodine-131, which contains 53 protons and 78 neutrons.
Did you know? There are many other uses of radionuclides, these include household smoke detectors, food preservation, and for monitoring mining processes.
The radioactive isotopes used in medicine are produced in nuclear power plants such as the Chalk River plant. In fact, the Chalk River plant alone actually supplies nearly half of the whole world's need for medical nuclides. In May of this year, a large volume leakage of radioactive water was found in the plant which caused the plant to shut down for at least 3 months.
The shortage has already been felt in provinces throughout Canada. In Saskatoon, health professionals have had to ration their remaining resources for the most urgent patients — which means that patients waiting for bone scans and other treatments in Saskatoon will have to wait longer.
Lisa Raitt, the Minister of Natural Resources Canada has said there is no reason to panic as the government negotiates with international partners to secure alternative supplies and hospitals look to other types of diagnostic tests to help manage during the shortage. These alternative diagnostic tests include CT scans, which aren't as powerful as nuclear diagnoses, but will have to make do for the time being. Because nuclear medicines have short shelf lives, the most urgent patients need to be treated as soon as possible.
Medical Isotopes in the News
Qian Qian (Rachel) Liu is a 4th year student at UBC who studies Medical Laboratory Sciences and conducts research in neuron development at the lab in the department of Neuroscience. In her free time, Qian Qian does a lot of volunteering in the community. She is involved with the Kids Help Phone organization in Vancouver, and volunteers on the phone lines of the Crisis Centre for Suicide Prevention.