To most people, “cobalt bomb” sounds like some super-powerful weapon of mass destruction. Tell them the first cobalt bomb was built and tested right here in Saskatchewan, and they’ll wonder what kind of crazed conspiracy theorist you are.
But the first cobalt bomb was indeed built and first tested here, 55 years ago–and far from being a weapon, it marked a milestone in the medical treatment of cancer.
Installed in Room 167 of the newly constructed cancer wing adjacent to the medical college at the University of Saskatchewan on August 17, 1951, the device didn’t actually look like a bomb. In fact, to any reader of the pulp science fiction magazines of the day, it probably looked more like a super-powerful ray gun—which is just what it was.
It was the brainchild of physics professor Dr. Harold Elford Johns, who had come to the U of S from the University of Alberta at the end of the Second World War.
Doctors had been using radiation to kill cancer cells since shortly after the discovery of X-rays and radium in the 1890s, but X-ray machines were expensive and complicated, and radium, formed into thin needles and implanted near tumours, was expensive and not powerful enough to be completely effective.
E. L. Herrington, the head of the U of S Physics Department in the 1940s, had begun research in the 1920s into the medical use of radiation, and it was thanks to him that the U of S was at the forefront of nuclear physics in Canada in the post-war years, and received Canada’s first betatron in 1948. A precursor to the Canadian Light Source synchrotron now located at the university, the betatron used magnets to accelerate electrons to an energy level of 25 million electron volts.
This generated powerful X-rays that could be used to treat cancer, but the machine was too expensive to operate for large-scale use, and the X-rays it produced weren’t always strong enough to reach tumours deep in the body.
However, scientists operating the National Research Council’s heavy water reactor in Chalk River, Ontario, had created a better source of radiation. Inside the reactor, cobalt, atomic weight 59, picked up an extra neutron in its nucleus to become the unstable isotope cobalt-60, 100 times more radioactive than radium–and far cheaper.
Dr. Johns began developing a machine that could direct cobalt-60 radiation to tumours in a safe, calibrated way. He had his design built by John MacKay, owner of Acme Machine and Electric Co. in Saskatoon.
Probably nicknamed the cobalt bomb because atomic bombs of all kinds were very much in the news in those years immediately after the Second World War, it consisted of a cylindrical cobalt-60 source, about 3 cm in diameter and 5.5 cm long, inside a lead shield.
The source, mounted on a wheel, could be turned to align with an opening in the shield, providing for precisely controlled emission of radiation.
In radiation treatment, a tumour is irradiated from several different directions to insure that it receives a high dose of radiation while the surrounding healthy tissue receives as small a dose as possible. Rapidly dividing cancer cells are more susceptible to radiation damage than are tissues whose cell repair and replacement mechanisms are operating normally.
Because the cobalt-60 radiation was so much more intense than anything else available at the time, it was particularly good for treating deep-seated tumours in the bladder, cervix and lungs.
The University of Saskatchewan team had its machine up and running on October 23, 1951. However, a team at London, Ontario’s Victoria Hospital became the first to use cobalt-60 in the treatment of a patient, on October 27. The London patient lived only a few weeks after treatment, but the first Saskatchewan patient, Molly Birtsch, a 43-year-old mother of four suffering from cancer of the cervix, was completely cured and lived until 1998.
The original machine remained in service until 1972, treating 6,728 patients over 21 years. It remains on display at the Saskatoon Cancer Centre.
The Canadian history magazine The Beaver summed up the cobalt bomb this way: “The machine looked like something out of a Buck Rogers episode. It was high-tech, 1950s style: whirring motors, shiny metal casing, men in lab coats milling around it, and an air of mystery about how it worked and what it did . . . It was futuristic, it worked miracles, and it was made in Canada.”
More specifically, it was made in Saskatchewan.
1 comments
I had never even heard of the cobalt bomb!