Patent US 4,547,893

A continuous wave fan beam tomographic system having continuous x-ray absorption values sampled at a sampling rate and means to provide a best-estimate of the x-ray absorption values at discrete points in time. The means to provide a best-estimate includes a continuous filter having a frequency range defined by the geometry of the mechanical system. Errors due to the statistical variation in photon emissions of the x-ray source are thereby minimized and the effective signal-to-noise ratio of signals is enhanced, which in turn allows a significant reduction in radiation dosage.