Penalized weighted least-squares image reconstruction for dual energy X-ray transmission tomography

We present a dual-energy (DE) transmission computed tomography (CT) reconst ruction method. It is statistically motivated and features nonnegativity co nstraints in the density domain. A penalized weighted least squares (PWLS) objective function has been chosen to handle the non-Poisson noise added by amorphous silicon (aSi:H) detectors. A Gauss-Seidel algorithm has been use d to minimize the objective function. The behavior of the method in terms o f bias/standard deviation tradeoff has been compared to that of a DE method that is based on filtered back projection (FBP). The advantages of the DE PWLS method are largest for high noise and/or low flux cases, Qualitative r esults suggest this as well. Also, the reconstructed images of an object wi th opaque regions are presented. Possible applications of the method are: a ttenuation correction for positron emission tomography (PET) images, variou s quantitative computed tomography (QCT) methods such as bone mineral densi tometry (BMD), and the removal of metal streak artifacts.