Less than 15 years ago, a linear accelerator equipped with multileaf collimators and portal imaging capability was considered state-of-the-art technology for external beam radiation treatment. Today, imaging plays a much bigger role in managing the patient position and anatomy over the entire course of treatment. With three-dimensional (3D) imaging increasingly becoming available in the treatment room, new image-guided radiation treatment (IGRT) techniques are being developed. is chapter focuses on megavoltage conebeam CT (MVCBCT), the most recent addition to the in-room 3DCT imaging systems. e main objectives of this chapter are to review MVCBCT technological features and to provide guidelines on the eective implementation of IGRT procedures based on the MVCBCT system.