X-ray backscatter systems are used for the screening of personnel for hidden weapons and other contraband. Unlike conventional radiographic x-ray systems, backscatter systems rely on detecting Compton scattered radiation, which allows for the source and the detector to be on the same side of the object being screened. The Security Technologies Group has two x-ray backscatter systems: a 50 kV Rapiscan Secure 1000 system; and a 100 kV AS&E SmartCheck system. These systems are used for dose characterization studies as well as image quality and radiation safety standards development.