Dual-gamma-source CT imaging system: Feasibility study with simulation and experiment

Our study demonstrated the feasibility of proposed CT imaging protocol and iterative reconstruction algorithm in both simulation and experimental studies. Polychromatic X-ray tube is used for imaging source of conventional CT system. However, conventional detector technique does not provide the capability to distinguish incident x-rays between different energy bins. Therefore, current reconstruction algorithms assumed and employed the mean values of the incident x-rays to reconstruct the 3D CT image. This assumption caused three main problems: formation of beam hardening, accuracy of quantitative CT imaging, and degradation of contrast, particularly for soft tissue. First, beam hardening causes cupping artifacts which can be observed as dark shades at the center of a CT image. Second, quantitative CT image refers to 3D image reconstructed by absolute value and conversion to Hounsfield units (HU). Quantitative CT is the active research field for normalized CT images and more accurate diagnosis. However, there are some limitations and difficulties to generate the quantitative CT image directly using polychromatic energy source. Third, polychromatic x-ray makes Compton scattering dominant and degrades the contrast of the soft tissue in CT images. To solve these problems, the use of monochromatic x-ray source is inevitable. We proposed a CT imaging protocol using multi-gamma-sources. We accordingly developed an iterative image reconstruction algorithm and validated it through both numerical and experimental studies. Our preliminary study demonstrated a feasibility of using multi-gamma-sources for CT imaging. The developed reconstruction approach would find applications in a high-resolution imaging with a large-focal-spot x-ray source or in a fast-scan x-ray CT imaging