Which isotope is commonly used in radiation therapy and has a half-life of 5.3 years?

Cobalt-60 is the isotope widely recognized for its application in radiation therapy, particularly in treating cancer. Its half-life of approximately 5.3 years is significant because it provides a balance between effective radiation exposure and manageable decay over time, allowing for a practical duration of treatment sessions without requiring constant replenishment.

In radiation therapy, the emitted gamma rays from Cobalt-60 are utilized to target and destroy cancerous cells. The isotope's ability to penetrate tissue and deliver a precise dose of radiation makes it a favored choice for many clinical protocols. Additionally, its decay provides a calibrated dose rate, ensuring that patients receive the intended amount of radiation during treatment.

Other isotopes mentioned, such as Iridium-192 and Cesium-137, also have applications in radiation therapy but do not possess the same half-life as Cobalt-60; Iridium-192 has a much shorter half-life, while Cesium-137 has a longer one. Tritium, while used in certain specialized applications and research, is not typically employed in radiation therapy.