All body cells can be damaged or killed by radiation, but tumor cells are more sensitive to radiation than normal cells. Radiation therapy uses this principle to damage beyond repair or kill the abnormal cancer cells in a tumor. Successful radiation therapy depends on the ability of the linear accelerator, or linac, to deliver a tumoricidal dose of radiation to the tumor while ensuring minimal radiation of normal tissue. The linac accurately produces, monitors, controls and conforms the radiation beam to the planned target.

The animation, How the Linear Accelerator Works, provides internal views of the linac and how the radiation is created.