What’s an isotope?
Dr. Dale Dewar, Saskatchewan family physician and executive director of Physicians for Global Survival, explains, “isotopes are forms of the same [chemical] element with different numbers of neutrons in the nuclei of their atoms. For example, 99 per cent of carbon exists in its most common form as Carbon 12 but it also exists as Carbon 13 (1%) and Carbon 14 (trace amounts).” Each of these forms is a different isotope.
“Another way of looking at isotopes is that they are slightly different forms of the same substance – and that medical isotopes are those used in medicine,” says Dewar.
What’s a medical isotope?
Medical isotopes, or radioisotopes, are radioactive. The radiation they emit as they decay can be used to diagnose or treat illness.
Diagnosis
When medical isotopes enter a patient’s body through injection, inhalation or ingestion, the radioactive particles can be read by scanners that create images of the internal structures of our bodies. Doctors can then use these images to pinpoint the location of cancerous tumors, watch the way that blood flows into the heart, or check kidney functioning.
There are other technologies that create medical images without medical isotopes. According to Dewar, “MRIs and ultrasounds produce pretty good results.” MRIs use magnetic and radiowaves to create three-dimensional images of organs and tissue. Ultrasounds use sound waves to create images of internal body structures, including fetuses in the womb.
Treatment
Medical isotopes can also be used to treat cancer. Dewar explains that in a treatment called brachytherapy a medical isotope is embedded directly inside the tumour. “This is frequently how radioisotopes are used for prostate cancer,” she says.
In brachytherapy, the radioactive particle that the isotopes emit does not penetrate flesh very deeply. Thus, it “destroys the tumor cells but is relatively safe for surrounding tissue,” says Dewar.