Intensity-modulated radiotherapy (IMRT) is an advanced type of radiation therapy delivered by a linear accelerator used to treat cancer and noncancerous tumors. IMRT uses advanced technology to manipulate beams of radiation to conform to the shape of a tumor. IMRT uses multiple small photon beams of varying intensities to precisely irradiate a tumor. The radiation intensity of each beam is modulated, and the beam shape changes throughout each treatment. The goal of IMRT is to conform the radiation dose to the target and to avoid or substantially reduce exposure of healthy tissue to limit the side effects of treatment. IMRT is particularly beneficial in complex cases when the target is directly adjacent to critical structures (head-and-neck cancers, brain tumors, prostate cancer).