Radiation oncology is a branch of oncology that uses radiation to treat cancer. Radiation can be used in place of, in conjunction with, or as an adjunct to other cancer treatments. A radiation oncologist is a physician trained in various forms of radiation treatment including internal radiation (brachytherapy) and external beam radiation therapy. Each radiation treatment is a detailed process that is carefully planned alongside physicists and dosimetrists. The radiation oncologist will work with other physicians to choose the best treatment plan available to each individual patient.