Spectral modulator with flying focal spot for cone-beam CT: a feasibility study

We present a new concept of full-scale cone-beam computed tomography (CT) spectral imaging with simultaneous scatter correction capability using a spectral modulator and flying focal spot technology. The design of the spectral modulator and the utilization of flying focal spot are investigated, revealing the feasibility of using the flying focal spot to improve the spectral data sampling for a stationary modulator. Based on our analytical analysis, with the flying focal spot, the spectral projection ray misalignment can be reduced by a factor of more than 8. For modulator design, common materials such as Cu, ZnSe, Mo, Ag and Sn could be good candidates for better energy separation at a given attenuation of photon flux. A proof-of-concept study of a Catphan600 phantom and an anthropomorphic chest phantom was conducted on a tabletop cone-beam CT system using a copper modulator and by moving the X-ray tube position by 1.24 mm in the X and Z directions to mimic the flying focal spot. We found the low and high energy rays were well aligned, while the scatter distribution remained constant between the flying focal spot positions.