A simple image based method for obtaining electron density and atomic number in dual energy CT

摘要

The extraction of electron density and atomic number information in computed tomography is possible when image values can be sampled using two different effective energies. The foundation for this extraction lies in the ability to express the linear attenuation coefficient using two basis functions that are dependent on electron density and atomic number over the diagnostic energy range used in CT. Material basis functions separate images into clinically familiar quantities such as 'bone' images and 'soft tissue' images. Physically, all basis function choices represent the expression of the linear attenuation coefficient in terms of a photoelectric and a Compton scattering term. The purpose of this work is to develop a simple dual energy decomposition method that requires no a priori knowledge about the energy characteristics of the imaging system. It is shown that the weighted sum of two basis images yields an electron density image where the weights for each basis image are the electron density of that basis image's basis material. Using the electron density image, effective atomic number information can also be obtained. These methods are performed solely in the image domain and require no spectrum or detector energy response information as required by some other dual energy decomposition methods.