Cobalt Blues: The Story of Leonard Grimmett, the Man Behind the First Cobalt-60 Unit in the United States

Brad Roth
4 min readMar 3
Cobalt Blues, by Peter Almond.

I recently read Cobalt Blues: The Story of Leonard Grimmett, the Man Behind the First Cobalt-60 Unit in the United States (Springer, 2013), written by Peter Almond. The treatment of cancer using the isotope cobalt-60 is now obsolete, but in the era just after World War II it was cutting-edge technology. In his prologue, Almond writes

[The British medical physicist Leonard George] Grimmett was an expert in the use of radium to treat cancer and in the safe handling and measurement of radiation and radioactive materials in clinical situations. He had spent the best part of his career devising better, safer, and more efficient ways to treat cancer with radiation and he remained in England during [World War II]… Then in 1948 while working for UNESCO in Paris he received an offer he could not refuse the, “…post as physicist to a new ‘Cancer Research Institute and Atomic Center’ in The University of Texas”, one of the original universities in the ORINS [Oak Ridge Institute of Nuclear Studies] consortium. Thus was set in motion the events that would lead Grimmett to Houston, Texas and to be the first person to publish, in 1950, the design of a cobalt-60 radiation therapy unit for the treatment of cancer. For the next 25 years cobalt-60 units would be the mainstay of cancer radiation therapy, treating millions of patients worldwide. Grimmett, however, would not live to see the completion of his work. This is his story.

Grimmett is a fascinating guy. As a young boy he learned to play the piano and was quite good. “He had worked his way through college playing for the silent movies, but with the advent of the ‘talkies,’ he had lost his income. He went to work at Westminster Hospital.” At Westminster and other hospitals he helped develop cancer treatment machines using radium, and later he established the medical physics program at the renowned M. D. Anderson Cancer Center. But he had other talents. He was a pilot, a scriptwriter, a gemologist, and jeweler. He’s remembered today primarily for developing a cobalt-60 therapy machine. Almond writes

It is not known for sure who first had the idea of replacing the radium in teletherapy units with a more suitable and less-expensive artificial radioactive substance. Grimmett, however, had been thinking about it for some years before he went to Houston, and a case can be made that he was the first.

What motivated him to use cobalt? “What Grimmett was looking for was an artificial radioactive isotope with gamma ray energies of 1–5 MeV with as long a half-life as possible that could be made in large quantities at a reasonable price.” He considered using sodium-24 for therapy. After 24Na beta decays it emits two gamma rays with energies of 4.1 and 1.4 MeV (see Fig. 17.9 of Intermediate Physics for Medicine and Biology). However, the half-life of 24Na is only 15 hours.

The idea that cobalt-60 might be a suitable replacement for radium first occurred to Grimmett while he was reading Physical Review in an air-raid shelter during World War II… Later, after the war, he would have read the paper by J. S. Mitchell in the December 1946 issue of the British Journal of Radiology [82]. This is often cited as the paper that initiated the cobalt-60 era. Mitchell specifically mentions cobalt-60 as a replacement for radium beam therapy, and he gave the half-life as 5.3 years and the gamma ray energies as 1.3 and 1.1 MeV. He also reported that it could be produced in “the pile” (nuclear reactor).

Why did Almond title his book Cobalt Blues? Grimmett had trouble obtaining the needed cobalt-60. It is a by-product of nuclear reactors. He first tried the reactor at Oak Ridge, but ended up getting it from a reactor on Chalk River in Canada. Incidentally, the book cover of Cobalt Blues is a lovely cobalt blue.

Grimmett was not the only person trying to use cobalt-60 to treat cancer. Almond briefly describes the other groups, including one in Canada by Harold Johns, and tries to sort out the various priority claims.

Unfortunately, Grimmett died unexpectedly and never saw his unit in use. His obituary in the Houston Chronicle begins

Doctor Grimmett, Cancer Expert, Dies Suddenly

Dr. Leonard G. Grimmett, 49, eminent physicist whose work in cancer research at M.D. Anderson Hospital, opened a whole new field of treatment of cancer, died of a heart attack at 1:10 a.m. Sunday at his home, 3238 Ewing.

I enjoyed Almond’s book. I learned much about the early years of the M. D. Anderson Cancer Center and about the issues that must be considered when building radiation therapy units. Readers of IPMB will find Cobalt Blues fascinating.

Originally published at

Brad Roth

Professor of Physics at Oakland University and coauthor of the textbook Intermediate Physics for Medicine and Biology.