Cobalt therapy is the medical use of

gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...

s from the

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

cobalt-60 Cobalt-60 (60Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2713 years. It is produced artificially in nuclear reactors. Deliberate industrial production depends on neutron activation of bulk samples of the monoisoto ...

to treat conditions such as

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

. Beginning in the 1950s, cobalt-60 was widely used in

external beam radiotherapy External beam radiotherapy (EBRT) is the most common form of radiotherapy (radiation therapy). The patient sits or lies on a couch and an external source of ionizing radiation is pointed at a particular part of the body. In contrast to brachyt ...

(teletherapy) machines, which produced a beam of gamma rays which was directed into the patient's body to kill tumor tissue. Because these "cobalt machines" were expensive and required specialist support, they were often housed in ''cobalt units''. Cobalt therapy was a revolutionary advance in radiotherapy in the post-World War II period but is now being replaced by other technologies such as

linear accelerator A linear particle accelerator (often shortened to linac) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear beam ...

History

Before the development of medical

s in the 1970s, the only artificial radiation source used for

teletherapy External beam radiotherapy (EBRT) is the most common form of radiotherapy (radiation therapy). The patient sits or lies on a couch and an external source of ionizing radiation is pointed at a particular part of the body. In contrast to brachyt ...

was the

x-ray tube An X-ray tube is a vacuum tube that converts electrical input power into X-rays. The availability of this controllable source of X-rays created the field of radiography, the imaging of partly opaque objects with penetrating radiation. In contrast ...

. Researchers found ordinary x-ray tubes, which used voltages of 50-150 keV, could treat superficial tumors, but did not have the energy to reach tumors deep in the body. To have the penetrating ability to reach deep-seated tumors without subjecting healthy tissue to dangerous radiation doses required rays with energy around a million electron volts (MeV), called "megavoltage" radiation. To produce a significant amount of MeV x-rays required potentials on the tube of 3-5 million volts (3-5 megavolts), necessitating huge, expensive x-ray machines. By the late 1930s these were being built, but they were available at only a few hospitals. Eldorado A

Radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

s produced

s in the megavolt range, but prior to

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

virtually the only radioisotope available for radiotherapy was naturally occurring

radium Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather t ...

(producing 1-2 MeV gamma rays), which was extremely expensive due to its low occurrence in ores. In 1937 the price of radium pergram, and the total worldwide supply of radium available for beam radiotherapy (teletherapy) was 50grams. The invention of the

nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from nu ...

in the

Manhattan Project The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project w ...

during World War II made possible the creation of artificial radioisotopes for radiotherapy.

Cobalt-60 Cobalt-60 (60Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2713 years. It is produced artificially in nuclear reactors. Deliberate industrial production depends on neutron activation of bulk samples of the monoisoto ...

, produced by neutron irradiation of ordinary

cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...

metal in a reactor, is a high activity gamma-ray emitter, emitting 1.17 and 1.33 MeV gamma rays with an activity of . The main reason for its wide use in radiotherapy is that it has a longer

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

, 5.27 years, than many other gamma emitters. However, this half-life still requires cobalt sources to be replaced about every 5 years. In 1949, Dr. Harold E. Johns of the

University of Saskatchewan A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, t ...

sent a request to the

National Research Council National Research Council may refer to: * National Research Council (Canada), sponsoring research and development * National Research Council (Italy), scientific and technological research, Rome * National Research Council (United States), part of ...

(NRC) of Canada asking it to produce cobalt-60 isotopes for use in a cobalt therapy unit prototype. Two cobalt-60 apparatuses were then built, one in

Saskatoon Saskatoon () is the largest city in the Provinces and territories of Canada, Canadian province of Saskatchewan. It straddles a bend in the South Saskatchewan River in the central region of the province. It is located along the Trans-Canada Hig ...

in the cancer wing of the University of Saskatchewan and the other in

London, Ontario London (pronounced ) is a city in southwestern Ontario, Canada, along the Quebec City–Windsor Corridor. The city had a population of 422,324 according to the 2021 Canadian census. London is at the confluence of the Thames River, approximate ...

. Dr. Johns collected depth-dose data at the University of Saskatchewan which would later become the world standard. The first patient to be treated with cobalt-60 radiation was treated on October 27, 1951, at the War Memorial Children's Hospital in London, Ontario. In 1961 cobalt therapy was expected to replace X-ray radiotherapy. In 1966,

Walt Disney Walter Elias Disney (; December 5, 1901December 15, 1966) was an American animator, film producer and entrepreneur. A pioneer of the American animation industry, he introduced several developments in the production of cartoons. As a film p ...

's lung cancer was treated with this procedure, but could not prevent his death. Dr.

Glenn T. Seaborg Glenn Theodore Seaborg (; April 19, 1912February 25, 1999) was an American chemist whose involvement in the synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Chemistry. His work i ...

, chairman of the

United States Atomic Energy Commission The United States Atomic Energy Commission (AEC) was an agency of the United States government established after World War II by U.S. Congress to foster and control the peacetime development of atomic science and technology. President H ...

Nobel Prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfr ...

winner and former chancellor of the

University of California The University of California (UC) is a public land-grant research university system in the U.S. state of California. The system is composed of the campuses at Berkeley, Davis, Irvine, Los Angeles, Merced, Riverside, San Diego, San Francisco, ...

, dedicated the first cobalt facility of the new Radiation Therapy and Nuclear Medicine Wing of the

Cedars of Lebanon Hospital Cedars-Sinai Medical Center is a nonprofit, tertiary, 886-bed teaching hospital and multi-specialty academic health science center located in Los Angeles, California. Part of the Cedars-Sinai Health System, the hospital employs a staff of over 2 ...

on January 11, 1963 supervised by Dr. Henry L. Jaffe, Director of the new department. A pioneer in the use of the nicknamed "cobalt bomb" the Cedars unit was licensed in 1948 by the Atomic Energy Commission.

Current use

The role of the cobalt unit has partly been replaced by the

, which can generate higher-energy radiation, and does not produce the

radioactive waste Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, rare-earth mining, and nuclear weapons r ...

that

s do with their attendant disposal problems. Cobalt treatment still has a useful role to play in certain applications and is still in widespread use worldwide, since the machinery is relatively reliable and simple to maintain compared to the modern linear accelerator.

Isotope

As used in

radiotherapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...

, cobalt units produce stable, dichromatic beams of 1.17and1.33 MeV, resulting in an average beam energy of 1.25MeV. Cobalt-60 has a

of 5.2713years.

References

{{Reflist, 30em, refs= {{cite magazine , author = , date = 1937-08-09 , title = Science: Radium , url = https://content.time.com/time/subscriber/article/0,33009,758086,00.html , url-status = live , magazine =

Time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to ...

, language = en-US , issn = 0040-781X , oclc = 1311479 , archive-url = https://web.archive.org/web/20220622155908/https://content.time.com/time/subscriber/article/0,33009,758086,00.html , archive-date = 2022-06-22 , access-date = 2022-06-22 , quote = Present price of radium is $25 per milligram, $25,000 per gram, $700,000 per ounce. , df = dmy-all {{cite web , url = https://cobalt60.usask.ca/ , title = Cobalt-60: Explore our legacy of nuclear medicine innovation , website =

, date = n.d. , access-date = 2022-06-22 , archive-url = https://web.archive.org/web/20220308050325/https://cobalt60.usask.ca/ , archive-date = 2022-03-08 , url-status = live , quote = In 1951, University of Saskatchewan medical physicist Dr. Harold Johns and his graduate students became the first researchers in the world to successfully treat a cancer patient using cobalt-60 radiation therapy. This innovative technology—dubbed the “cobalt bomb” by the media—revolutionized cancer treatment and saved the lives of millions of cancer patients around the world. , df = dmy-all {{cite web , url = https://www.london.ca/business/Planning-Development/secondary-plans/Documents/Old%20Victoria%20Hospital/Cultural-Heritage-Asssessment-South-Street-Hospital-Buildings.pdf#page=46 , title = Cultural Heritage Assessment: Buildings in the South Street Hospital Complex, London, Ontario , author = , date = , page = 46 , location = , isbn = , language = , trans-title = , archive-url = https://web.archive.org/web/20200504041250/https://www.london.ca/business/Planning-Development/secondary-plans/Documents/Old%20Victoria%20Hospital/Cultural-Heritage-Asssessment-South-Street-Hospital-Buildings.pdf#page=46 , archive-date = 2020-05-04 , access-date = 2020-05-03 , url-status = live , quote = It is perhaps fitting, given the symbolic emphasis that the War Memorial Children’s Hospital placed on turning the spoils of war to the benefits of peace, that this facility became the first place in the world to use the Cobalt-60 Beam Therapy Unit (the Cobalt Bomb) in the treatment of a Cancer patient, on October 27, 1951. {{cite web , url = https://www.lhsc.on.ca/about-lhsc/celebrating-the-60th-anniversary-of-the-worlds-first-cancer-treatment-with-cobalt-60 , title = Celebrating the 60th anniversary of the world's first cancer treatment with Cobalt-60 radiation , date = 2011-10-27 , website =

London Health Sciences Centre London Health Sciences Centre is a hospital network in London, Ontario and is collectively one of Canada's largest acute-care teaching hospitals. It was formed in 1995 as a result of the merger of University Hospital and Victoria Hospital. In a ...

, language = en-CA , access-date = 2022-06-23 , url-status = live , archive-url = https://web.archive.org/web/20220427192817/https://www.lhsc.on.ca/about-lhsc/celebrating-the-60th-anniversary-of-the-worlds-first-cancer-treatment-with-cobalt-60 , archive-date = 2022-04-27 , quote = On October 27, 1951, the world's first cancer treatment with Cobalt-60 radiation took place at Victoria Hospital. This marked an important milestone for both the fight against cancer and Canada's emergence as a leader in the field of radiotherapy. Today, London Health Sciences Centre is pleased to acknowledge the 60th anniversary of this tremendous medical breakthrough. , df = dmy-all {{cite news , author = , date = 1961-11-01 , title = "New Era" In Cobalt Treatment Of Cancer , url = https://news.google.com/newspapers?nid=1301&dat=19611101&id=DIgVAAAAIBAJ&sjid=RuYDAAAAIBAJ&pg=790,7885261 , url-status = live , work =

The Sydney Morning Herald ''The Sydney Morning Herald'' (''SMH'') is a daily compact newspaper published in Sydney, New South Wales, Australia, and owned by Nine. Founded in 1831 as the ''Sydney Herald'', the ''Herald'' is the oldest continuously published newspaper ...

, language = en-AU , issue = 29649 , edition = Late , page = 14 , issn = 0312-6315 , lccn = sn84035933 , oclc = 226369741 , archive-url = https://web.archive.org/web/20220528151121/https://news.google.com/newspapers?nid=1301&dat=19611101&id=DIgVAAAAIBAJ&sjid=RuYDAAAAIBAJ&pg=790,7885261 , archive-date = 2022-05-28 , access-date = 2022-06-23 , via =

Google News Google News is a news aggregator service developed by Google. It presents a continuous flow of links to articles organized from thousands of publishers and magazines. Google News is available as an app on Android, iOS, and the Web. Google rel ...

, df = dmy-all {{cite news , last1 = Markel , first1 = Howard , date = 2018-12-17 , title = How a strange rumor of Walt Disney's death became legend , url = https://www.pbs.org/newshour/health/how-a-strange-rumor-of-walt-disneys-death-became-legend , url-status = live , department = Health , work =

PBS NewsHour ''PBS NewsHour'' is an American evening television news program broadcast on over 350 PBS The Public Broadcasting Service (PBS) is an American public broadcaster and non-commercial, free-to-air television network based in Arlington, Virg ...

, language = en-US , archive-url = https://web.archive.org/web/20220618120446/https://www.pbs.org/newshour/health/how-a-strange-rumor-of-walt-disneys-death-became-legend , archive-date = 2022-06-18 , access-date = 2022-06-23 , quote = The always energetic man struggled to go back to the Disney studios after the operation, but the chemotherapy and cobalt X-ray treatments drained him of both his creative and physical powers. He was rushed back to St. Joseph's Hospital two weeks later and died of "circulatory collapse" on the morning of Dec. 15. , df = dmy-all {{cite book , chapter = Annex A. Radionuclides of the ICRP-07 collection , title = Annals of the ICRP {{! Nuclear Decay Data for Dosimetric Calculations , publisher =

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, date = 2008 , volume = 38 , series = ICRP Publication 107 , issue = 3 , pages = 35–96 , doi = 10.1016/j.icrp.2008.10.002 , doi-access = free , issn = 0146-6453 , isbn = 978-0-7020-3475-6 , lccn = 78647961 , pmid = 19285593 , last1 = Eckerman , first1 = K. , last2 = Endo , first2 = A.

External links

public domain image of cobalt machine
Radiation therapy Cobalt

History

Current use

Isotope

See also

References

External links