Cobalt, specifically the isotope cobalt-60, creates precise bursts of gamma radiation used to treat otherwise inoperable cancer tumors in patients that have deformities in blood vessels or within the brain, according to the U.S. Environmental Protection Agency. Radioactive cobalt is shielded to prevent harm to operators.
Cobalt-60 is used for radiation therapy because the gamma radiation beam is precise and it does little, if any, damage to surrounding tissue. Cobalt radiation therapy can be used anywhere on the body, but it is particularly useful in the brain, notes the American Brain Tumor Association. Cobalt-60 directs 200 beams of radiation toward cancerous cells while the person's head is held in place by a special rigid frame. Treatment lasts anywhere from several minutes to a few hours. After the procedure, which requires a local anesthetic, the individual can return to normal activities.
Cobalt devices are still widely used in developing countries, as of December 2014. The radiation has a range of about 3 feet, and cobalt emits two radioactive bursts between 1.17 and 1.33 megavolts each. The cobalt device can rotate around to precisely target a tumor from more than one direction, while simultaneously protecting the machine's operator. Cobalt-60 sources must be replaced every six or seven years. This type of therapy has been replaced by electron beam radiation therapy in hospitals, according to Health Physics Society.