What radioactive substance is used for brachytherapy?

Iridium-192 is an isotope of Iridium which has a ½ life of 74 days. For treatment, the source is deployed from a small machine about the size of a college dorm refrigerator. Iridium-192 emits gamma rays with an average energy of 380KeV, which results in limited penetration in the body away from the treated area. Most brachytherapy treatments with Iridium-192 are used for breast, uterine, and cervical cancer in our departments.