![]() Sources are usually replaced about once per half-life or about every 5 years for Co-60. Some Transmission Factors on Field Size and Treatment Depth in External Beam Radiation Therapy (EBRT) Using the Theratron Equinox 100 Cobalt 60 Machine. Often the output of a teletherapy machine is state d in Rmm (roentgens per minute at 1 m) as a rough guide for the source strength. This diameter is significantly larger than modern linear accelerator source sizes and causes the Cobalt 60 teletherapy machines to have larger penumbras. Sources are cylindrical in shape with a diameter of 1-2cm and a height of about 2.5cm. Typical sources have an activity of 5,000-10,000Ci which is able to produce a dose rate of 100-200cGy/min for an source-to-axis distance of 80cm. Co-60 is a superior radionuclide to alternatives, such as Ra-226 and Cs-137, because of its higher energy and specific activity (mCi/g) which allows for greater radiation output with a smaller source size. Cobalt-60 (half-life 5.27 years) is the largest revenue-producing commercial radioisotope in the world. ![]() The buildup region of the photon dose distribution extends to a depth of 5mm, providing some skin sparing.Ĭobalt 60 is produced in a nuclear breeder reactor by neutron bombardment of cobalt 59 and has a half life of 5.27 years. ![]() Approximately 10% of the source photons are lower energy scattered photons. This cobalt therapy machine was manufactured by Atomic Energy of Canada Limited. Cobalt-60 teletherapy units are able to generate a clinical photon beam with a mean energy of 1.25MeV, similar to the mean energy of a 4MeV photon beam generated by a linear accelerator. In 1951, Canada was the first country to develop cobalt-60 radiation treatment.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |