Radiation Physicists and Dosimetrists use computer models to plan radiation treatment. This computerized treatment planning allows the treatment to be delivered more accurately, both in terms of the "beam shape" that is achieved with precise collimator settings and in terms of the angles and directions used to deliver the radiation to the cancer. By using the computer to help "focus the x-ray beam," the Radiation Oncologist can deliver the radiation precisely to cancer, delivering a minimal amount of radiation to healthy tissues.

The radiation treatment planning models usually use a three-dimensional (3D) re-creation of the patient's anatomy. Images of the patient are acquired from the CT Simulator then sent by network or computer disk to the radiation treatment planning computer.