Abstract: Systems and methods for determining body composition by combining dual-energy x-ray (DXA) technology with three-dimensional (3D) optical technology and/or bioimpedance technology. A multi-modality scanning system may include a dual-energy x-ray source and an x-ray detector mounted to opposing sides a c-arm and configured to scan a patient on a optically translucent table. The system may also include one or more 3D optical imaging devices to capture 3D optical images of the patient substantially concurrently with the emission of the dual energy x-rays. A bioimpedance machine may also be included in the multi-modality scanning system. Data based on the dual-energy x-rays may be combined with the data from the 3D optical images and/or the bioimpedance data to generate values of at least three compartments selected from: bone, fat tissue, lean tissue, dehydrated lean tissue, and water.