Internal radiation therapy for treating cancer is also known as brachytherapy. The procedure involves placing the radioactive material into or near the cancer site to kill the cancerous cells. Brachytherapy is used in treating various cancers, such as cancers of the brain, breast, thyroid, eye, uterus, gallbladder, skin, head and neck, rectal, prostate, and lungs. The advantages of brachytherapy include an optimal dose at the target site and minimal damage to the surrounding tissues.