Image guided radiation therapy (IGRT) has experienced radical advancements in technology and clinical utilization over the past decade. IGRT has become one of the most important frontiers in radiation therapy (RT) innovation and research and numerous technologies and clinical use cases have been developed. IGRT has been able to reduce uncertainties in RT delivery and also to improve the ability to deliver radiation dose to tumors while sparing normal tissues. Very important aspects of IGRT implementation have been techniques to deal with tumor and patient motion during treatment. Another important use case for IGRT is evaluation of patient changes over the course of treatment and their effect on the overall adequacy of treatment. This presentation discusses various approaches to IGRT and how this technology can be used to potentially improve clinical practices. At the conclusion of this activity, the learner will be able to do the following: 1. Explain available IGRT technologies and major considerations for their use. 2. Discuss the practical clinical application of IGRT. 3.Describe the principles for quality control of IGRT systems.