Harold Johns

Harold JohnsHarold Johns (1915-1998)
Built one of the first two cancer-treatment machines using cobalt-60 radioisotopes in 1951

Harold Elford Johnswas born in Szechuan, China, on July 4, 1915, the son of educational missionaries from Ontario. His family stayed there until 1926 when they had to leave due to the political turmoil in China. Upon returning to North America, the family moved to Tacoma, Washington, Brandon, Manitoba and eventually Hamilton, Ontario where Harold attended McMaster University and obtained a Bachelor of Science in Mathematics and Physics in 1936. He then attended the University of Toronto where he received a MA in 1937 and a PhD in Physics in 1939.

From 1939 to 1945, Dr. Johns served as Professor in the Physics Department at the University of Alberta.  In 1945, he was invited to join the Physics Department of the University of Saskatchewan in Saskatoon and to spend half his time starting the medical physics group at the new Saskatchewan Cancer Commission in Regina.  Dr. Johns’ most obvious achievement during this phase of his career was the development of the cobalt-60 cancer therapy unit in 1951. The cobalt bomb, as it is known, is a nuclear radiation device which revolutionized the treatment of cancers located deep in the body, where previous radiation therapies had proven ineffective.

Cobalt cancer unit
Cobalt-60 cancer therapy unit.

In 1956 Dr. Johns moved to Toronto to become head of the Physics Division at the Ontario Cancer Institute. He also joined the faculty of the University of Toronto where he taught and researched in the Departments of Medical Biophysics, Radiology, and Physics. During his scientific career, he published over 200 peer-reviewed papers, trained over 100 graduate students, many of whom hold key positions in the medical radiation research field in Canada and around the world, won many prestigious awards including the Order of Canada, and published four editions of The Physics of Radiology, the premier textbook in its field.

After a lengthy battle with Parkinson’s Disease, Dr. Harold Johns passed away on Aug. 23, 1998 in Kingston, Ontario.


Canadian Nuclear Society, http://media.cns-snc.ca/history/pioneers/harold_johns/hejohns.html.