1. An apparatus for producing three dimensional tomographic images of an object irradiated by a plurality of rays of plane parallel collimated radiation (unattenuated beam) transmitted through said object comprising: (a) a two-dimensional electro-optical imaging detector having active pixels for simultaneously recording a two-dimensional image that measures attenuated transmitted radiation from multiple stacked planes after said plane parallel collimated radiation has passed through the object, said detector including an energy converter, an image format altering device, and a readout device, wherein said detector's active pixels have a detective quantum efficiency greater than 0.05, a total signal dependent background less than 10 percent of the signal from the unattenuated beam and a useful dynamic range greater than 10, and deviations of geometric linearity that are less than 10 pixels in the recorded image; (b) means for obtaining projection data from said attenuated transmitted radiation, and (c) means for computing a three dimensional reconstructed image of attenuation coefficients of said object from said projection data.