1. A system for reconstructing a 3D volume, comprising: a surface acquisition system comprising a light source and an image sensor for characterizing the surface contour of a patient; an X-ray imaging system for acquiring X-ray projection data of the patient from a plurality of angular positions; a controller programmed with instructions to synchronize the 3D surface contour characterization from the surface acquisition system with the acquired X-ray projection data; and a processor that executes a motion reduction method that uses the acquired X-ray projection data and the generated 3D surface contour characterization to reconstruct a 3D volume.