Sci‐Fri PM Imaging‐07: The feasibility of using FBP to reconstruct electron densities from attenuation corrected scatter sinograms

Breast CT is an emerging modality which aims to generate high quality 3D images. At these energies a large number of the incident x‐ray photons are scattered, resulting in a reduced contrast to noise ratio. As the reduction of dose and the detection of blurred calcifications and other poorly visible lesions are diagnostically important, we have developed an approach which uses both the primary and scattered photons to obtain low‐dose conventional CT and electron density (ρ e ) images. In the absence of attenuation and for a spherical detector, electron densities can be reconstructed using a mono‐energetic pencil beam and conventional Filtered Back Projection (FBP). In place of a spherical detector we have simulated a more practical detector ring with an angular width of 5 degrees and capable of measuring both scattered and primary photons. In practice, attenuation cannot be neglected and Attenuation Correction Factors (ACF) were calculated for each detector using an initial estimate of the electron density based on reconstructed linear attenuation coefficients. The corrected measurements were summed at each rotation and translation of the x‐ray beam to yield a scatter sinogram. This sinogram was processed using FBP to yield an image which provides, in an iterative manner, a new estimate of the electron density. This approach has shown that we are capable of reconstructing electron densities in simple geometries with errors ranging from 2 to 4%. Polyenergetic beam hardening and multiple scattering corrections are being investigated, for future incorporation into the algorithm.