A method and apparatus for using a flat panel detector to determine bone mineral density are provided. The apparatus includes a dual energy X-ray emitter, a flat panel detector for receiving X-rays sent from the X-ray emitter, and may optionally include an image corrector, adapted to emit corrected image information. The apparatus also includes a basis material decomposer that includes a calibration database, the decomposer being adapted to create a bone image and a soft tissue image. The apparatus further includes a bone mineral density calculator that is adapted to compute bone mineral density from the first image, and a display for displaying at least the computed bone mineral density. A method for using a flat panel detector to detect multiple disease states is also provided. The method includes emitting X-rays from a dual energy X-ray source through an area of a patient's body sought to be imaged and receiving X-rays with a flat panel detector. The method also includes generating multiple images, using dual energy X-ray absorptiometry, to detect for a first disease state and a second disease state and analyzing the images for the first and second disease states. The first disease state includes lung cancer, breast cancer, pneumonia, chronic obstructive pulmonary disease, tuberculosis, bone fracture or an abnormally sized or shaped organ and the second disease state comprises osteoporosis.