Harold E. Johns

Harold Elford Johns, OC (4 July 1915 – 23 August 1998) was a Canadian medical physicist, noted for his extensive contributions to the use of ionizing radiation to treat cancer.

Johns was born to missionary parents in Szechuan, China. He lived in China until 1926, when political unrest there prompted his parents to return to North America. After spending time in Tacoma, Washington, and in Brandon, Manitoba, his family settled in Hamilton, Ontario.

In Hamilton, Johns pursued a degree in mathematics and physics at McMaster University, and he completed his bachelor of science degree (B.Sc.) in 1936. He then moved to the University of Toronto, where he earned his Master of Arts and Doctor of Philosophy (Ph.D.) degrees in physics in 1939.

Johns' graduation coincided with the start of World War II. For the duration of the war, he taught physics, mathematics, radar systems, and radio navigation to newly recruited airplane pilots as part of the British Commonwealth Air Training Plan. Based on his radiography and physics experience, Johns was also involved in non-invasive X-ray testing of metal aircraft castings. A meeting in August 1946 with William Valentine Mayneord, while Mayneord was at the Atomic Energy Project at Chalk River, Ontario, contributed to Johns's making a career in medical physics.

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