Thorium-223 is a radioactive isotope of thorium, which is a naturally occurring element. It has a half-life of about 25.5 days, making it relatively short-lived compared to other isotopes. Thorium-223 is primarily used in medical applications, particularly in targeted alpha therapy for treating certain types of cancer, such as prostate cancer. In this therapy, Thorium-223 emits alpha particles that can destroy cancer cells while minimizing damage to surrounding healthy tissue. This targeted approach helps improve treatment outcomes and reduce side effects, making it a promising option in the field of nuclear medicine.