Image Reconstruction for Hybrid True-Color Micro-CT

Abstract

X-ray micro-CT is an important imaging tool for biomedical researchers. Our group has recently proposed a hybrid “true-color” micro-CT system to improve contrast resolution with lower system cost and radiation dose. The system incorporates an energy-resolved photon-counting true-color detector into a conventional micro-CT configuration, and can be used for material decomposition. In this paper, we demonstrate an interior color-CT image reconstruction algorithm developed for this hybrid true-color micro-CT system. A compressive sensing-based statistical interior tomography method is employed to reconstruct each channel in the local spectral imaging chain, where the reconstructed global gray-scale image from the conventional imaging chain served as the initial guess. Principal component analysis was used to map the spectral reconstructions into the color space. The proposed algorithm was evaluated by numerical simulations, physical phantom experiments, and animal studies. The results confirm the merits of the proposed algorithm, and demonstrate the feasibility of the hybrid true-color micro-CT system. Additionally, a “color diffusion” phenomenon was observed whereby high-quality true-color images are produced not only inside the region of interest, but also in neighboring regions. It appears harnessing that this phenomenon could potentially reduce the color detector size for a given ROI, further reducing system cost and radiation dose.

Hybrid Spectral Micro-CT: System Design, Implementation, and Preliminary Results

“…The described reconstruction technique utilizes the respective strengths of each imaging chain to produce images with both high spatial and contrast resolution. This concept was theoretically proven in [15], and the results from the prototype system implementation in this paper support its assertions.…”

“…Numerical simulation algorithms were developed based on Xu et al [15] and the aforementioned prototype system/CA phantom design. Global grayscale and interior spectral projections of the phantom were simulated with parameters matching the prototype system scan, including: source flux and spectrum; source-to-object and source-to-detector distances; projection angles and numbers; detector configuration, pixel size, conversion efficiency, and energy binning.…”

“…The reconstruction algorithm is fully described and derived in [15] and [16], respectively, but summarized here for convenience.…”

“…Xu et al [15] reported a hybrid spectral micro-CT system design that incorporated the spectral interior and energyintegrating global imaging chains into a rotating gantry configuration. The benefits of a rotating gantry design, compared to a rotating sample stage, are obvious for biomedical researchers as many potential applications require in vivo scans (e.g., small rodents).…”

“…In order to overcome these limitations, Xu et al proposed to combine a spectral imaging chain with an energy-integrating imaging chain [15]. The latter provides wide-beam ("global") grayscale projections of the sample, while the former provides narrow-beam ("interior") spectral projections covering a small field of view (FOV).…”