In this study, we develop 2D and 3D tomographic non-destructive tests for detecting fluorescence X-rays using a 2D CdTe array. Experiments were conducted using various phantoms and image-reconstruction methods. In general, conventional computed tomography analyzes materials according to attenuation coefficients and is highly dependent on the densities of the materials; thus, it is difficult to discriminate materials that have similar densities, even if their atomic numbers differ. In our research, materials were exposed to X-rays, and both conventional transmission images and fluorescent X-ray images were reconstructed using the information from characteristic X-rays detected using a 2D CdTe planar detector array. Since atoms have their own characteristic X-ray energies, our system was able to discriminate materials of the same or similar density if the materials had different atomic numbers. Additionally, the transmission and characteristic X-ray images were combined to analyze the positions, densities, and atomic numbers of the unknown materials. Several image-reconstruction methods were applied; the reconstructed images were compared to determine an optimized algorithm for fluorescence X-ray computed tomography.
21 Figures and Tables
Fig. 1. Principle of characteristic X-ray in the case of a full energy transfer .
Fig. 10. Overlaid images.
Fig. 11. 3D rendered images for (a) simulation and (b) experiment.
Fig. 12. Reconstructed images of various pipes (a) Al, (b) Fe, and (c) Cu.
Fig. 2. FXCT combined with conventional CT.
Fig. 3. Geometry of the 3D FXCT system. (a) Disassembled components and (b) assembled components.
Fig. 4. Phantoms with inner metals. (a) Plastic phantom and (b) PVC pipe phantom.
Fig. 5. Energy spectra of inner phantom materials. (a) Ce (34.72 keV), (b) Gd (43 keV), and (c) Bi (77.11 keV).
Fig. 6. 2D projection images (unit: counts) based on the detection of (a) transmitted X-rays, (b) characteristic X-rays (Ce), (c) characteristic X-rays (Gd), and (d) characteristic X-rays (Bi).
Fig. 7. 3D reconstructed images based on the detection of (a) transmitted X-rays, (b) characteristic X-rays, and (c) the fused image.
Fig. 8. 3D reconstructed image of each detector with PVC pipe. (a) Transmitted X-ray image, (b) characteristic X-ray image, and (c) the fused image.
Fig. 9. Comparison of 3D reconstructed images. (a) Phantoms, (b) simulation results, and (c) experimental results.
TABLE I SPECIFICATIONS OF THE X-RAY GENERATOR
TABLE II SPECIFICATIONS OF XMARU 1215CF+ DETECTOR
TABLE III SPECIFICATIONS OF AJAT PID 350 DETECTOR
TABLE IV COMPARISON OF A CdTe POINT DETECTOR WITH A CdTe ARRAY
TABLE IX HVLs AND TVLs OF EACH PIPE [mm] –
TABLE V SNR OF EACH RECONSTRUCTED IMAGE
TABLE VI MEASURED DIAMETER OF EACH RECONSTRUCTED IMAGE [mm]
TABLE VII MEASURED FWHM OF EACH DIFFERENTIATED CURVE FOR THE EDGE OF THE RECONSTRUCTED IMAGE [mm]
TABLE VIII ESTIMATED MASS OF EACH RECONSTRUCTED COMPONENT [g]
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