Date of issue: June 17, 1988
Printer: Ashton-Potter
Series: Canada Day – Science and Technology. Canadian Innovations in Energy, Food, Research and Medicine
Design: Roger Hill
Cobalt Therapy
Physicians started treating cancer with radiation soon after radium was discovered in 1898. In 1951, scientists at Atomic Energy of Canada manufactured a machine that was able to produce gamma radiation from a cobalt-60 source located deep within its reinforced head. The emitted gamma rays had sufficient energy – 1.17 and 1.33 megavolts – to penetrate deep into human tissue and cause cancer cell death. Much more powerful and less expensive to produce than radium, this quickly became the standard of care.
The world’s first calibrated cobalt-60 cancer therapy program was developed at the University of Saskatchewan by physicist Harold Johns and his colleagues. In November 1951, following 11 weeks of machine calibration, therapy was administered to its first patient, who lived 47 more years until her death at the age of 90. The machine has largely been replaced by linear accelerators, which can produce greater voltages and do not produce radioactive waste.
The Stamp
The stamp shows a patient receiving radiation treatment for breast cancer. The formula for the radioactive cobalt isotope 60CO and representations of its emitted gamma rays are shown at the left. The first-day cover shows a diagram of the machine as it appeared in a patent.
