Typical half-lives for gamma emission are immeasurably short (from about 10 -9 to 10 −14 second). When the half-lives for gamma emission are measurable, the nucleus in the higher energy state before radiating a photon and the one in the lower energy state are called nuclear isomers. See also isomer.

What you experience during brachytherapy depends on your specific treatment. Radiation can be given in a brief treatment session, or it can be placed in the body permanently. Temporary brachytherapy(high-dose-rate brachytherapy) is often done in short sessions. The radioactive material might be in your body for a short amount of time. This can range from a few minutes to about 20 minutes. You might have one or two sessions a day over a number of days. During high-dose-rate brachytherapy, you lie in a comfortable position. Depending on the treatment, you may receive anesthesia. The radiation therapy team puts the radiation device into place. This may be a simple tube or tubes placed inside a body cavity or small needles inserted into the cancer. The radioactive material is inserted into the brachytherapy device with the help of a machine. The radiation therapy team leaves the room during the treatment session. The team members observe from a nearby room where they can see and hear you. You may feel some discomfort during brachytherapy. If you feel uncomfortable or have any concerns, tell your care team. Once the radioactive material is removed from your body, you won't give off radiation or be radioactive. You aren't a danger to other people, and you can go on with your usual activities. Wherein Permanent brachytherapy, radioactive material is placed in your body permanently. This is a common treatment for prostate cancer. The radioactive material is typically placed by hand. An imaging test, such as ultrasound or CT, might be used to make sure the material is in the right place. You are under anesthesia during the procedure. You shouldn't feel any discomfort once the radioactive material is in place. Your body will emit low doses of radiation from the area being treated at first. Usually the risk to others is low. You might need to limit how much time you spend around children and anyone who is pregnant. The amount of radiation in your body will get lower over time. These limits will end.

Radioactive half-life is the time required for half of the radioactive atoms present to decay. Some radionuclides have half-lives of mere seconds, but others have half-lives of hundreds or millions or billions of years. Uranium-238. Thorium-232. Radioactive decay is the emission of energy in the form of ionizing radiation.

2 90 Sr/ 90 Y is such a source, emitting a continuous spectrum of fast electrons up to a maximum energy of 0.546/2.27 MeV. 3 The half life is 27.7 yr/64 hr. 3. Gamma rays are electromagnetic radiation emitted by excited nuclei in their transition to lower nuclear energy levels (following beta decay).