Volume 8, Number 8 January 5, 2001

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U of S ‘cobalt-60’ physicist Johns added to Science & Engineering Hall of Fame

Dr. Harold Johns (1915-1998)

Former U of S medical physicist Harold Johns (1915-1998) was posthumously inducted into the Canadian Science and Engineering Hall of Fame in a Nov. 30 ceremony at the Canada Science and Technology Museum in Ottawa.

One of the founders of medical physics, Johns made an internationally significant contribution to medical research that has improved treatment for cancer and relieved the suffering of countless patients worldwide.

Johns, who worked at the U of S from 1945-56, was best known for his development of the cobalt-60 cancer therapy unit in 1951. Also known as the ‘cobalt bomb,’ the unit revolutionized the treatment of cancers located deep in the body, where previous radiation therapies had proven ineffective. It has been estimated that seven million people around the world have benefitted from cobalt-60 therapy.

Johns also developed a table of x-ray dosage rates – at various depths in human tissues, for a variety of energies, and for various types of treatment equipment – which is still used today as the basis for x-ray dosage tables.

At the Ottawa ceremony, Peter Hackett, Vice-President of Research at the National Research Council of Canada (NRC), presented a plaque to Johns’ daughter, Gwen Greenstock.

Hackett noted that Johns trained in mathematics and physics, taught the practical aspects of radar and radio navigation to air force pilots, and tested aircraft castings with x-rays. This practical orientation in physics led him to his life’s work – the application of radiation in cancer therapy.

In 1948, Johns and his U of S physics colleagues Leon Katz and Ertle Harrington were instrumental in obtaining Canada’s first betatron accelerator for research into the forces at work in the atomic nucleus. This 25-million-volt device facilitated research in the basic sciences of physics, chemistry and biology, as well as cancer treatment.

It was from this work that the U of S went on to become a centre of accelerator expertise and is now the site of the Canadian Light Source synchrotron project.

Johns established a program in medical physics that focused on x-ray radiation and radioactive isotopes for cancer treatment. The radiation research group worked on the problem of determining the appropriate doses of radiation and controlling the radiation during treatment.

Johns went on to the University of Toronto, where he helped establish the department of medical biophysics. He eventually became department chair and established a multidisciplinary graduate program.

The Canadian Science and Engineering Hall of Fame is a partnership of the Canada Science and Technology Museum Corp. and the NRC. It seeks to promote Canadian achievements and careers in science and engineering.

To date there are 26 inductees, chosen by a selection committee composed of distinguished Canadians who represent top Canadian scientific and engineering organizations.

The judges identify inspiring role models for young Canadians, who have had a lasting impact on society.

For more information, contact communications.office@usask.ca

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