Cobalt therapy or cobalt-60 therapy is the medical use of gamma rays from cobalt-60 radioisotopes to treat conditions such as cancer. The first patient to be treated with Cobalt-60 radiation was treated on October 27, 1951, at Victoria Hospital in London, Ontario. In 1961 cobalt therapy was expected to replace X-ray radiotherapy. The role of the cobalt unit has partly been replaced by the linear accelerator, which can generate higher energy radiation. Cobalt treatment still has a useful role to play in certain applications and is still in widespread use worldwide, since the machinery is relatively reliable and simple to maintain compared to the modern linear accelerator. No photographer credited, undated.