Giants in Radiation Oncology: Harold Johns, PhD

Harold Johns demonstrates the operations of a cobalt-60 therapy unit to Princess Margaret and Lord Snowdon during the opening of the new wing of the Princess Margaret Hospital in Toronto in 1967. Photo credit: David Milne

Harold E. Johns, PhD, the first full-time cancer care-focused medical physicist in Canada, has been called the father of megavoltage radiation and the educator of generations of radiation oncologists, diagnostic radiologists, nuclear medicine physicians and medical physicists. Born in Sichuan, China, to missionary parents, he first arrived in North America in 1926, initially to Tacoma, Washington, but later, to Hamilton, Ontario. Following receipt of his BS in mathematics and physics from McMaster University, he received his MA and PhD in physics from the University of Toronto. He completed his training in 1939, just as Canada, a part of the British Commonwealth, was entering World War II. He remained in Canada during the war, serving at the University of Alberta, teaching radar systems and radio navigation skills to pilots. During that time, he also developed the methodology for X-ray testing of metal aircraft castings. After the war, he returned to the University of Saskatchewan to continue his physics career and to supervise radium and orthovoltage X-ray therapy at the university hospital. The province of Saskatchewan was uniquely suited to his future efforts, having proposed development of a radium institute as early as 1922, and creating the first cancer control agency in Canada in 1930.

In 1946, while attending a meeting at the Atomic Energy Canada, Chalk River Laboratory (CRL) in Ontario, he met, and was influenced by William Valentine Mayneord, a pioneering British medical physicist who had been stationed in Canada during the war to study the radiological aspects of atomic energy. This chance encounter would change the course of his career and the future of radiation oncology. At the meeting, he learned of the CRL repository of cobalt-60, and immediately recognized the potential clinical use of the material for cancer management. Upon his return to Saskatchewan, CRL provided him with sufficient quantity of the isotope to study its medical utilization. Johns’ group, along with colleagues in London, Ontario, designed and constructed prototype cobalt-60 external beam radiation therapy devices, and introduced the modern clinical megavoltage era when they treated their first patient in October 1951. The Saskatchewan unit remained in active clinical care for the next 21 years, until it was finally decommissioned in 1972.

In 1953, at the age of 38, with his OCI and UT colleague John Robert Cunningham, Johns published the first edition of their textbook “The Physics of Radiology,” which was to become a standard training and reference texts for radiation oncologists, diagnostic radiologists, nuclear medicine physicians and medical physicists for generations. The text has gone through multiple printings and was translated into Spanish, Russian and Chinese. The two continued to be lead authors through the fourth edition published in 1983. Cunningham died in 2020; the fifth, and current edition of the text is edited by their former colleagues.

In 1956, Dr. Johns was named head of the physics division at the Ontario Cancer Institute (OCI) at Princess Margaret Hospital in Toronto, and in 1958, he joined the Graduate Department of Medical Biophysics at the University of Toronto (UT), which was initially conceived to foster interaction between physicists, radiologists and radiotherapists (much later to be designated as radiation oncologists). He was named chair of that department in 1958. During his tenure at UT, he was a leader in studying the chemical processes secondary to radiation damage in tissue. In 1971, during a sabbatical year at the Institute for Cancer Research (ICR) in Sutton, Surry, UK, he did significant research in medical imaging, especially isotope imaging and mammography.

Dr. Johns received numerous awards and honors for his work as a Canadian scientist, including Fellowship in the Royal Society of Canada (1951), the Henry Marshall Tory Medal of the Royal Society of Canada (1971), Officer of the Order of Canada (1978), Medal of Honour from the Canadian Medical Association (1983), and the W.B. Lewis Award from the Canadian Nuclear Society (1985). In 1977, he was awarded Honorary Fellowship in the American College of Radiology, the highest honor bestowed on non-members by that organization. In 1988, he was honored by the government of Canada when they issued a postage stamp with his likeness. In 2000, he was inducted into the Canadian Science and Engineering Hall of Fame.

Dr. Johns was an avid water skier, actively pursuing the sport until he was 75, and was described as the life of parties, dragging a piano into the living room for group singing. Sadly, for the last 30 years of his life, he battled progressive Parkinson’s disease. He married Alice Sybil Hawkins in 1940, and at the time of his death in 1998, they had been married for 58 years. The Johns had three daughters and six grandchildren.