Applications of Radioisotopes
Why nuclear imaging is necessary in medical diagnoses and research
The closing of a Canadian nuclear plant may leave many wondering why nuclear imaging is necessary for health.
The recent shutdown of Chalk River Nuclear Laboratories (CRNL) in Ontario means that medical facilities in Canada and around the world are facing a shortage of isotopes required for medical diagnoses. As CRNL provides approximately two-thirds of the world’s supply of medical isotopes, hospital centres are scrambling to maintain patient care. But what are radioisotopes and how do they contribute to health?
Isotopes and positrons
Positron Emission Tomography (PET), also known as nuclear imaging, is a technique that uses radioactive isotopes to visualize specific areas in the body for both diagnostic and research purposes.
As radioactive substances, isotopes are subject to decay. This decay leads to the emission of positrons, which have the opposite charge of electrons. When positrons and electrons collide, they annihilate each other, and this annihilation produces two kinds of gamma rays that are emitted in opposite directions. This gamma ray emission is what is detected by a PET scanner.
The amount of radiation that a patient or study subject receives from the isotopes during a PET scan is comparable to the amount received from other medical procedures but less than X-rays or CT scans. The amount of radiation decays very quickly, and there are no known side effects. The amount received is thought to be equivalent to the background environmental radiation from living in a major city for several months, or the equivalent of two chest X-rays.
Research
Research scientists integrate radioactive isotopes into chemical compounds that travel to specific organs in the body. For example, glucose is often used, as it is a substance used in large quantities by the brain.
During studies, researchers inject subjects with a glucose-hungry isotope before asking them to perform specific tasks under a PET scanner. The areas of the brain that are functional at the time of the task, i.e. the areas that absorb the glucose, will show on the image created by the PET scanner.
Medical applications
A recent review carried out by Dr. Yee Ung of the Odette Cancer Centre in Toronto on PET imaging and its use for diagnosing lung cancer showed that PET imaging is highly accurate when differentiating between benign and malignant lesions as small as 1 cm.
The NewYork-Presbyterian University Hospital of Columbia and Cornell uses PET technology in the treatment of heart pathologies to determine heart function, detect signs of coronary artery disease, identify blocked arteries, and evaluate damage after a heart attack.
Because of the many uses for these radioactive compounds, the world medical community is indeed on the lookout for alternative supplies since the CRNL shutdown. In the meantime, seriously ill patients everywhere may have to wait that much longer for key answers about their health.
References:
Moore, O. (December 7, 2007). New Reactors To Have Ended Dependence on Chalk Rivers. The Globe and Mail. Retrieved December 9, 2007.
Ung, Y.C., Maziak, D.E., Vanderveen, J.A., Smith, C.A., Gulenchyn, K., Lacchetti, C., Evans, W.K. (2007). 18 Fluorodeoxyglucose Positron Emission Tomography in the Diagnosis and Staging of Lung Cancer: A Systematic Review. J Natl Cancer Inst, 99, 1753-1767.
NewYork-Presbyterian University Hospital of Columbia and Cornell. (n.d.). Nuclear Imaging for Heart Disease. Retrieved December 9, 2007.
