An x-ray imaging system provides both scanning radiography and computed tomography by means of a modified C-arm geometry that provides improved angular rotation. Estimation techniques are used to produce missing projections of the complete tomographic projection set, and a limited size detector (50) reduces the amount of data required for reconstructing tomographic images of compact objects of unique composition within the patient (such as the spine (65)). The introduction of image artifacts caused by external volumes to the field of view is reduced by employing dual energy techniques to isolate the internal structure from the external volumes.