Cesium131

Cesium-131 is a radioactive isotope of cesium with mass number 131 (chemical symbol Cs-131). It is not found in nature and is produced artificially in nuclear reactors or particle accelerators for specialized medical uses and research. Cs-131 is used primarily in brachytherapy, where small sealed sources deliver localized radiation to a tumor from inside or next to the treatment area.

The isotope has a relatively short half-life of about 9.7 days. It decays mainly by electron capture to xenon-131 and emits low-energy photons, which enables effective dose delivery to targeted tissue while limiting long-term exposure to surrounding healthy tissue. The sealed nature of brachytherapy sources containing Cs-131 helps confine radiation and protect patients, medical staff, and the community.

In clinical use, Cs-131 is often embedded in small capsules or ribbons and implanted directly into tumors or surgical beds. Its rapid dose delivery and faster decay compared with some other radionuclides can reduce treatment times and shorten the period of radiation protection required for patients and caregivers. Cs-131 is one option among radionuclides employed in brachytherapy, alongside others such as iodine-125 and palladium-103, with the choice depending on tumor type, location, and clinical goals.

Safety and regulatory considerations involve strict handling, shielding, and disposal procedures for sealed radioactive sources. Agencies overseeing radiation safety provide guidelines for storage, transport, use, and end-of-life management to minimize exposure and environmental impact.