Application of CT Simulation Technique for Virtual Fecal Tagging in CTC

Abstract

An integrative CT simulation technique is presented that creates realistic CT images of virtual fecal-tagged material that was added to given clinical DICOM CT images. The energy spectrum of the CT X-ray source, the energy-dependent attenuation, and the scattering properties of the soft tissue and tagging material were incorporated in the generation technique for the DICOM image-based virtual sinograms, followed by CT reconstruction reflecting the vendor-specific filtering kernels. Dark band artifacts were generated by appropriate combining of beam-hardening and -scattering effects into the generation procedure for the virtual sinograms. We used a set of simple numerical phantoms to assess the basic behavior of artifact production. A reference set of CTC images with and without tagging material and artifacts was used for evaluation of the realism of the simulated results. The level of realism was evaluated in terms of the artifact strength and patterns around the added tagging material, compared to real tagging images. The results showed that our CT simulation technique provides sufficient realism for virtual fecal-tagged images that reflect a chain of physical and numerical processes, including beam hardening, scattering, and vendor-specific kernel filtered backprojection. The technique presented has the potential to be used as a tool for investigating the effect of tagging materials on image quality and to gauge how well the electronic cleansing technique performs.