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An x-ray radiographic system consisting of two detectors in tandem, or a sandwich detector, can produce dual-energy image from a single-shot exposure. Subtraction of two images obtained from the two detectors can produce a sharper image through an unsharp masking effect if the two images are formed at different spatial resolutions. This is indeed possible by incorporating different thicknesses of x-ray conversion layers in the detectors. In this study, we have developed a microtomography system with a sandwich detector in pursuit of high-resolution bone-enhanced small-animal imaging. The results show that the bone-enhanced images reconstructed from the dualenergy projection data provide higher visibility of bone details than the conventionally reconstructed images. The microtomography with the single-shot dual-energy sandwich detector will be useful for the high-resolution bone-enhanced small-animal imaging. K : Computerized Tomography (CT) and Computed Radiography (CR); Medical-image reconstruction methods and algorithms, computer-aided diagnosis 1Corresponding author.

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A: A novel sandwich-style single-shot detector has been built by stacking two indirectconversion flat-panel detectors for preclinical dual-energy mouse imaging. Although this single-shot method is more immune to motion artifacts compared with the conventional dual-shot method (i.e., fast kVp switching), it may suffer from reduced image quality because of poor spectral separation between the two detectors. Spectral separation can be improved by using an intermediate filter between the two detector layers. Adversely, the filter reduces the number of x-ray photons reaching the rear detector, hence probably increasing image noise. For a better design and practical use of the sandwich detector for single-shot dual-energy imaging, imaging performances of each detector layer in the sandwich detector are investigated for various spectral-separation extents and applied tube voltages. The imaging performances include the modulation-transfer function, the Wiener noise-power spectrum, and the detective quantum efficiency. According to the experimental results, impacts of the intermediate filter on the imaging performances of each detector layer are marginal. The detailed experimental results are shown in this study.

For a dedicated x-ray inspection of printed-circuit boards (PCBs), a bench-top planar cone-beam computed tomography (pCT) system with a flat-panel detector has been built in the laboratory. The system adopts the tomosynthesis technique that can produce cross-sectional images parallel to the axis of rotation for a limited angular range. For the optimal operation of the system and further improvement in the next design, we have evaluated imaging performances, such as modulation-transfer function, noise-power spectrum, and noise-equivalent number of quanta. The performances are comparatively evaluated with the coventional cone-beam CT (CBCT) acquisition for various scanning angular ranges, applied tube voltages, and geometrical magnification factors. The pCT scan shows a poorer noise performance than the conventional CBCT scan because of less number of projection views used for reconstruction. However, the pCT shows a better spatialresolution performance than the CBCT. Because the image noise can be compensated by an elevated exposure level during scanning, the pCT can be a useful modality for the PCB inspection that requires higher spatial-resolution performance. K : Computerized Tomography (CT) and Computed Radiography (CR); Inspection with x-rays 1Corresponding author.