Clinical application of Compton and photo-electric reconstruction in computed tomography: preliminary results

Although computed tomography has demonstrated some promise in the direction of quantative radiology, valuable information related to the varying response of tissues to x-rays of different energy is still not utilized on a routine basis. Advancements in a method proposed by Alvarez and Macovski for decomposing dual-spectra CT projection data into its material-dependent Compton and photo-electric components are described. Results are presented to demonstrate that such a separation can be performed. Reconstructed images of separated Compton and photo-electric data obtained from clinical scans are shown. With the improvements described, the Compton images begin to approach the quality of conventional reconstructions with evidence of improved polychromatic correction. The photo-electric data, while separable, suffers from unacceptable noise level. Analysis of this difficulty is presented, with recommendations for future improvement by careful selection of the effective energy of the low energy spectrum. The encouraging results suggest that this technique warrants continued development and evaluation.