An x-ray imaging system, such as a mobile radiography unit, includes a plurality of stationary carbon nanotube based x-ray sources to be selectively energized. A circuit enables a selected subset of the radiation sources to be energized while another subset may be disabled. A light source may be attached to the support arm of the mobile radiography unit and a source of electric power is configured to energize the light source upon operator contact with the unit. The plurality of stationary x-ray sources may be used to capture a plurality of 2-D projection images of a subject to reconstruct a 3-D image thereof. The 3-D image is used to generate a 2-D projection image of the subject.