Split-Filter Computed Tomography

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Abstract
A simple technique for obtaining dual energy information from a single computed tomography (CT) scan is described. The method involves filtering the 2 halves of the X-ray fan beam differently. During a 360.degree. scan, this split-filtration geometry results in dual energy measurements of each cross-sectional path through the patient. A dual energy noise analysis, valid for polychromatic X-ray beams, is presented and used to determine the optimal parameters for the split-filter scans. Using the theoretically optimal split-filter design installed on a commercial CT scanner, photoelectric and Compton images of a head phantom were obtained. Recombination of the photoelectric and Compton components of attenuation at arbitrary energies demonstrates the ability to remove spectral artifacts from conventional CT images.