About the UHN Cyclotron

photo of PETtrace 800 cyclotron

The cyclotron is located at the Toronto General Hospital. The cyclotron enables the ability to provide cutting-edge radiopharmaceuticals to UHN-affiliated and other Ontario hospitals. These radiopharmaceuticals are primarily used for Positron Emission Tomography (PET) scans and assist doctors in diagnosis and treatment planning for patients with cancer and other serious diseases.

What is a cyclotron?

A cyclotron is a machine that is used to produce radioactive isotopes. The machine accelerates particles (such as hydrogen ions) to a very high speed and directs them to a target where a controlled reaction forms a radioactive isotope. For example, in order to make Fluorine-18 (F-18), which is by far the most common isotope used for PET imaging, the beam is directed onto a target containing water enriched with the non-radioactive isotope Oxygen-18 (O-18).

How are isotopes turned into radiopharmaceutical products?

Once the radioactive isotopes have been created by the cyclotron, chemistry techniques are used to incorporate these isotopes into radiopharmaceuticals for medical imaging and research. In the case of Fluorine-18 (F-18), the isotope would likely be bound to tracers commonly used to scan cancer patients for diagnosis or treatment planning, or they may be used in research or clinical trials.

Most of the chemistry work is done in sealed, lead-lined "hot cells". The lead lining shields the radiation so that staff handling the radioactive material do not receive any radiation exposure.

photo of the hot cell  

Currently, the only isotopes produced using the UHN cyclotron are Fluorine-18 and Nitrogen-13. Gallium-68 is also obtained in the facility from a generator supply.

Are there any risks to individuals working at UHN or living nearby?

No. Cyclotrons have been built and operated worldwide since the 1930s, and are considered to be a clean and safe nuclear technology. It is important to note that the cyclotron cannot operate or produce radioactivity without electrical power. Unlike a nuclear reactor, a cyclotron can simply be shut off like a light bulb. The cyclotron facility has also been designed to ensure radiation exposure to any adjacent area is actually kept below normal background levels. For example, although the cyclotron unit itself is relatively small, much of the space in the facility is taken up by extra thick concrete and lead shielding.

Staff who work in the cyclotron facility receive specialized training to work safely with radioactive material. The facility also contains several safety monitoring systems, security features and interlocks which are tested on a regular basis. Special ventilation systems guard against accidental releases of radioisotopes outside the facility and were designed to ensure that even in a worst-case scenario that there would be no measurable risk to the public. Emissions from the facility are monitored continuously. Since the cyclotron facility began operations in 2013, there have been no releases at levels that would be significant to our staff, patients or community.

Does the facility produce radioactive waste?

The cyclotron facility produces very little radioactive waste. All radioactive isotopes have "half-lives," which is the time it takes for half of a given sample of radioactive material to undergo radioactive decay. This means that after one half-life, half of the material is no longer radioactive. Most isotopes produced from a cyclotron have very short half-lives; for F-18, the half-life is just under 2 hours. The table below shows how much of a sample would still be radioactive after a certain amount of time has passed.

IsotopeHalf-life1 Hour4 Hours1 Day
Fluorine-18 (F-18)110 minutes69% remaining22% remaining0% remaining
Nitrogen-13 (N-13)10 minutes1.5% remaining0% remaining0% remaining
Gallium-68 (Ga-68)68 minutes54% remaining8.5% remaining0% remaining

Due to the short half-lives, any quantities of radioactivity remaining after production will quickly decay to background levels and the products can then be safely discarded through standard chemical waste streams.

The short half-lives also mean that bulk quantities of radiopharmaceuticals cannot be stored for future use and must be produced on a daily basis. This is the reason why more and more hospitals are installing their own cyclotron facilities as demand for these tracers grows; it is far more efficient to generate short-lived isotopes close to the hospital so they can be used before they decay away. There are several other cyclotrons operating in Toronto as well as in Hamilton, London and Ottawa.

Is the radioactive material transported safely?

The volume of radioactivity produced by the cyclotron is relatively small in scale. A typical production run of F-18 amounts to a volume of less than 20mL, about the same size volume as an espresso coffee. The radiopharmaceuticals are transported in shielded containers that meet international standards. Anyone packaging or transporting radioactive material is also required to have special training in accordance with Transport Canada and federal regulations.

Who has oversight for the cyclotron and its products?

A cyclotron facility that produces and uses radioactive materials requires licensing through the Canadian Nuclear Safety Commission (CNSC). The CNSC has regulated the production and use of all nuclear material in Canada since 1946. They are mandated to ensure the safety of staff, the public and the environment.

The design of the entire cyclotron facility, including safety considerations for staff and the general public, has been reviewed and approved by the CNSC. They also review and approve the Radiation Safety program, policies and procedures. As a part of their oversight program, periodic inspections of the facility are performed by CNSC staff members. Regular reports are also made by the cyclotron facility to the CNSC, and licence renewals ensure the regulator reviews the entire operation on a scheduled basis.

For more information on the CNSC, visit the Canadian Nuclear Safety Commission

Where can I get more information on radiation and radiation safety in Canada?

The Canadian Nuclear Safety Commission has excellent educational resources about radiation and radiation safety in Canada:


Any significant events will be posted here for public disclosure in accordance with the UHN Public Information and Disclosure policy.

Contact Us

If you have questions about the cyclotron facility, please contact the UHN Radiation Safety Office at 416 340 4800 ext. 4801 or

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