Harold Johns

Portrait of Harold Johns by Irma Coucill

Irma Coucill
Permanent Collection of The Canadian Medical Hall of Fame
c.
© CHIN 2001


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.
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.

© CHIN 2001

Inspired by the suggestion that cobalt-60 might be a better source of radiation for cancer therapy, Johns applied to the National Research Council at Chalk River for a sample of cobalt-60. With one of the three samples produced at Chalk River in 1951, Dr. Johns designed a unit capable of safely delivering the radiation. Having been carefully tested and calibrated for three months, Dr. Johns’ unit was first used to treat a patient on 8 November 1951.

His textbook ""The Physics of Radiology,"" first published over a half-century ago, is used by radiation specialists throughout the world to this day, and ""cobalt-60"" is a treatment still widely used for therapeutic purposes. It provides a reliable and cost-effective source of radiant energy in the battle against cancer.
Inspired by the suggestion that cobalt-60 might be a better source of radiation for cancer therapy, Johns applied to the National Research Council at Chalk River for a sample of cobalt-60. With one of the three samples produced at Chalk River in 1951, Dr. Johns designed a unit capable of safely delivering the radiation. Having been carefully tested and calibrated for three months, Dr. Johns’ unit was first used to treat a patient on 8 November 1951.

His textbook ""The Physics of Radiology,"" first published over a half-century ago, is used by radiation specialists throughout the world to this day, and ""cobalt-60"" is a treatment still widely used for therapeutic purposes. It provides a reliable and cost-effective source of radiant energy in the battle against cancer.

© CHIN 2001

Theratron

This is a commercial model of the cobalt-60 cancer therapy unit designed by Harold Johns.

Made by Atomic Energy of Canada, Ltd., Ottawa, Ontario, Canada
Canada Science and Technology Museum
c. 1957
© CHIN 2001


cobalt 60

This is a video clip describing the development and use of cobalt 60 for cancer therapy.

"Dr. Johns, along with graduate student Silvia (Fidora?) applied basic physics with a pain-staking thoroughness to develop cobalt 60. This major technological achievement could now treat deep seated and difficult to access tumours through cobalt therapy."

Courtesy of the Canadian Medical Hall of Fame.

© CHIN 2001


Learning Objectives

The learner will:

  • Identify and appreciate the way history and culture shape a society’s science and technology
  • Describe scientific and technological developments, past and present, and appreciate their impact on individuals and societies
  • Describe how Canadians have contributed to science and technology on the global stage

Teachers' Centre Home Page | Find Learning Resources & Lesson Plans