Tumor radiotherapy is a local treatment method that uses radiation to treat tumors. Radiation includes α, β, and γ rays generated by radioisotopes and x-rays, electron beams, proton beams, and other particle beams generated by various x-ray therapy machines or accelerators. The history of radiotherapy is only a few decades, but with the help of the development of CT imaging technology and computer technology, it has developed from two-dimensional radiotherapy to three-dimensional or even four-dimensional radiotherapy technology.