Daily setup for radiotherapy is frequently accomplished with the aid of digitally acquired X-ray projection or volumetric imaging. These images may be kV or MV energies and may be acquired using computed radiography or digital radiography receptors. These are generally compared to the planning CT either directly or to DRRs generated from that CT images proceed by a treatment planning system. The ability to localize daily treatments maybe limited by choices made in beam-energy for localization images, setting used when acquiring the planning CT and/or daily CT, settings used in generating DRRs, and/or techniques used to process images after acquisition. This course is intended to review the basic physics of projection and CT imaging, processing and display. We will also discuss generation of DRRs, image processing, and methods for determine daily alignment from projection and volumetric imaging. At the conclusion of this activity, the learner will be able to do the following: 1. Define the differences in information between kVP and MV images projection and Volumetric Images. 2. Manage acquired and reference images for daily setup. 3. Identify trade off and choices involved in generating and viewing digital images.