This document summarizes intensity modulated radiotherapy (IMRT) and its advantages over conventional radiotherapy. IMRT allows for superior dose distribution and better sparing of normal tissues by modulating the radiation beam intensity inside each treatment field. It provides more conformal dose coverage of irregularly shaped tumor targets while further reducing dose to nearby healthy tissues and critical organs. IMRT planning requires defining treatment goals and optimizing dose constraints using computer algorithms to determine the optimal intensity patterns delivered via multileaf collimators.