# Cobalt-60 teletherapy

Source: https://onco.cc/technologies/cobalt-60-teletherapy/  
OnCo record `cobalt-60-teletherapy` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The machine that made curative radiotherapy widely available from the 1950s: a sealed cobalt-60 source in a rotating head. Linacs replaced it in rich countries, but cobalt units still treat many patients where power and servicing are unreliable.

## Summary

The first cobalt-60 units were installed in Canada in 1951 and for thirty years were the workhorse of radiotherapy worldwide, delivering megavoltage gamma rays with far better depth dose than the X-ray tubes before them. Linear accelerators, with sharper beams, higher output and no decaying source, replaced them in high-income countries from the 1980s. Cobalt units remain in service in many low- and middle-income countries because they need little electricity and maintenance, though their source replacement and security are growing concerns and the IAEA is helping countries move to linacs.

## Fields

- Kind: Technology
- Status: historic
- Last checked: 2026-09-16
- Tags: radiation-wave1
- Principle: A high-activity cobalt-60 source emits 1.25 MeV gamma rays; the shielded head rotates around the patient to deliver megavoltage external beam therapy.
- Since: 1951
- Strengths: Simple and robust; Low running cost; Made megavoltage therapy available worldwide
- Limitations: Source decays and must be replaced; Broader penumbra and lower dose rate than a linac; Security of the radioactive source

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Cobalt_therapy

## Connected records

- fronts: [Radiation Therapy](https://onco.cc/fronts/radiation/)
- technologies: [Global oncology and access in low- and middle-income countries](https://onco.cc/technologies/global-oncology-access/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [Radiotherapy access and the global machine gap](https://onco.cc/technologies/radiotherapy-access-gap/)

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