Harold Johns distinguished himself at the dawn of the nuclear age by pursuing research on new radiation sources for cancer therapy. His research included the development of ’’cobalt 60’’ cancer treatment, which used radioactive cobalt to produce gamma rays-superceding the strength of the x-ray--as a source of radiation.

Dr. Johns’ interest throughout his scientific career was in the application of physics to medical concerns. Born in 1915 in Chengdu, China, Dr. Johns received his bachelor’s degree from McMaster University in 1936, and his Master’s (1937) and Ph.D. (1939) in Physics at the University of Toronto.

In 1949 Dr. Johns brought an innovation to the field of cancer therapy with a betatron, a unit for producing very high-energy x-rays with better penetration characteristics for deep tumours. With it he introduced the era of "megavoltage" radiation therapy. During this time he developed methods to determine appropriate radiation doses for patients.
Canadian Heritage Information Network
Canada Museum of Science and Technology, Musée de la civilisation, Stewart Museum, Canadian Medical Hall of Fame, Museum of Health Care at Kingston, University Health Network Artifact Collection, University of Toronto Museum of Scientific Instruments, University of Toronto Museum Studies Program

© CHIN 2001

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