Journal of X-Ray Science and Technology - Volume 19, issue 3
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Journal of X-Ray Science and Technology is an international journal designed for the diverse community (biomedical, industrial and academic) of users and developers of novel x-ray imaging techniques. The purpose of the journal is to provide clear and full coverage of new developments and applications in the field.
Areas such as x-ray microlithography, x-ray astronomy and medical x-ray imaging as well as new technologies arising from fields traditionally considered unrelated to x rays (semiconductor processing, accelerator technology, ionizing and non-ionizing medical diagnostic and therapeutic modalities, etc.) present opportunities for research that can meet new challenges as they arise.
Abstract: Traditional helical cone-beam Computed Tomography (CT) is based on the assumption that the entire cross-section of the scanned object is covered by x-rays at each view angle. Because of the size limitation of planar detector, the traditional helical cone-beam CT scanning is restricted when the cross-section of the object is larger than the field of view (FOV) of the CT system. The helical cone-beam CT scanning based on FOV half-covered can almost double the FOV, whose…mechanism is simple and the scanning efficiency is the same as that of traditional helical cone-beam CT. During reconstruction, the extended helical cone-beam FDK algorithm (called half-covered helical FDK for short) is developed, and the computational efficiency of this algorithm is high. But the reconstruction image has truncation error. Regarding this problem, this paper extends the idea of 2D local reconstruction to 3D half-covered helical cone-beam CT, and develops an improved half-covered helical cone-beam CT reconstruction algorithm based on localized reconstruction filter. Experimental results indicate that the presented algorithm well solves the truncation error of the half-covered helical FDK algorithm, improves the quality of the reconstruction image. And for the noise projection data, the presented algorithm can suppress noise and get better results. Moreover, the reconstruction time is much less.
Abstract: Human hair fibers are primarily composed of keratin protein, characterized by a very high content of cysteine, a sulfur-containing amino acid, which ordinarily forms cystine via a disulfide bond. It is known that some cystine residues are converted to cysteic acid during permanent waving or hair coloring, although details of their distribution and extent are still unclear. In this study, by using difference in XANES profiles of cystine and cysteic acid at the S-K absorption edge,…the formation of cysteic acid was confirmed for homogenized samples of permed or bleached hair. Furthermore chemical mapping of cysteic acid was performed on hair-section samples with X-ray contact microscopy. The peripheral region, cuticle, in bleached hair showed the highest content of cysteic acid compared with the other parts, while permed hair showed relatively uniform distribution. This finding suggests that perming and bleaching damage hair by different mechanisms.
Abstract: Purpose: To investigate image artifacts caused by a standard treatment couch on cone-beam CT (CBCT) images from a kV on-board imager and to develop an algorithm based on spatial domain filtering to remove image artifacts in CBCT induced by the treatment couch. Methods: Image artifacts in CBCT induced by the treatment couch were quantified by scanning a phantom used to quantify CT image performance. This was performed by scanning the phantom setup on a regular treatment couch and…in air with the kV on-board imager. An algorithm was developed to filter image artifacts from the treatment couch by processing of cone-beam radiographic projections using two scans: one scan of the phantom and treatment couch and a second scan of the treatment couch only. This algorithm is based on a pixel-by-pixel removal of beam attenuation due to the treatment couch from each projection of the phantom and couch scan. The net couch-filtered projections were then used to reconstruct CBCT. Results: We found that the treatment couch causes considerable image artifacts: CT number uniformity is degraded and varies as much as 15%, and noise in CBCT scans with phantom plus couch (3.5%) is higher than for the phantom in air (1.5%). The spatial domain filtering technique reduces noise by more than 1.5%, improves uniformity by a factor of 2, and removes ringing and streaking artifacts related to the standard treatment couch in CBCT reconstructed from couch-filtered projections. This filtering technique was tested successfully to filter other hardware objects such as a patient immobilization body-fix frame. Conclusions: The standard treatment couch causes image artifact in CBCT from kV on-board imaging systems. The spatial domain filtering technique developed in this work improves image quality of CBCT by preprocessing the projections prior to CBCT reconstruction. This technique might be useful to filter other hardware objects from CBCT which may contribute to the degradation of image quality.
Abstract: Drilling is one of the most complex techniques for making ancient stone or jade implement or adornment. However, related research on ancient stone or jade drilling technology lags behind, for there are rare records or discovery of the ancient drilling tools. Drilling marks are very useful information for analysis and research of the ancient drilling techniques. The traditional information acquisition methods are very difficult to apply effectively on smaller perforations. In this paper, we introduced a…new nondestructive method to solve the observation difficulty problem. The ancient bead was scanned by 3D-μCT system. Then through T-FDK algorithm, improved NL-means denoising algorithm and high accurate calibration, the 3D geometrical information of micro-drilling marks on outer and inner wall of the perforation were reconstructed. The experimental results proved that this method can provide key information for the analysis of the ancient stone drilling technique and ancient jade authentication.
Keywords: Ancient drilling technique, three dimensional micro-computed tomography, image denoising, T-FDK algorithm
Abstract: Radiation therapy using antiprotons is a potential interesting future modality. Energetic antiprotons penetrate matter with almost near identical stopping powers and radio biological effectiveness (RBE) as protons in the region well before the Bragg peak region. When the antiprotons come to rest at or near the Bragg peak, they annihilate releasing almost 2 GeV per annihilation. Most of the energy is carried away on the average by 4 to 5 energetic pi mesons. The annihilations lead…to roughly a doubling of physical dose with additional increase due to RBE in the Bragg peak region. This study was undertaken in order to assess the effect of the products of antiproton annihilations on depth dose profiles through MCNPX simulations. Beams of protons and antiprotons with varying energies and field sizes were used in the simulations. In our study, for 126 MeV beam, the peak to entrance (P/E) dose ratios of 4.9 for protons and 8.9 for antiprotons were found which gave the antiproton/proton P/E dose ratio equals to 1.8. This is in excellent agreement with the previous result obtained with FLUKA simulations.
Abstract: Circular cone-beam CT is one of the most popular configurations in both medical and industrial applications. The FDK algorithm is the most popular method for circular cone-beam CT. However, with increasing cone-angle the cone-beam artifacts associated with the FDK algorithm deteriorate because the circular trajectory does not satisfy the data sufficiency condition. Along with an experimental evaluation and verification, this paper proposed a curve-filtered FDK (C-FDK) algorithm. First, cone-parallel projections are rebinned…from the native cone-beam geometry in two separate directions. C-FDK rebins and filters projections along different curves from T-FDK in the centrally virtual detector plane. Then, numerical experiments are done to validate the effectiveness of the proposed algorithm by comparing with both FDK and T-FDK reconstruction. Without any other extra trajectories supplemental to the circular orbit, C-FDK has a visible image quality improvement.
Abstract: In this paper, we propose a new metal artifacts reduction algorithm based on fractional-order total-variation sinogram inpainting model for X-ray computed tomography (CT). The numerical algorithm for our fractional-order framework is also analyzed. Simulations show that, both quantitatively and qualitatively, our method is superior to conditional interpolation methods and the classic integral-order total variation model.
Keywords: Metal artifacts reduction, image inpainting, total variation, fractional order, X-ray computed tomography
Abstract: In this paper, we present some new relationship between the divergent beam projection and the Radon transform. An application of our results is to implement the Radon inversion from divergent beam projection.
Abstract: Differential phase contrast imaging computed tomography (DPCI-CT) is a novel x-ray inspection method to reconstruct the distribution of refraction index rather than the attenuation coefficient in weakly absorbing samples. In this paper, we propose an iterative reconstruction algorithm for DPCI-CT which benefits from the new compressed sensing theory. We first realize a differential algebraic reconstruction technique (DART) by discretizing the projection process of the differential phase contrast imaging into a linear partial…derivative matrix. In this way the compressed sensing reconstruction problem of DPCI reconstruction can be transformed to a resolved problem in the transmission imaging CT. Our algorithm has the potential to reconstruct the refraction index distribution of the sample from highly undersampled projection data. Thus it can significantly reduce the dose and inspection time. The proposed algorithm has been validated by numerical simulations and actual experiments.
Keywords: X-ray, phase contrast imaging, compressed sensing and computed tomography
Abstract: A rapid method for the analysis of iron concentrates by gel sample preparation and x-ray fluorescence (XRF) spectrometry detection was developed. The solution digested by aqua regia was mixed with agarose, and then agarose was dissolved in the boiling solution and the mixture became quasi-solid gel at ambient temperature. The quasi-solid gel was detected by XRF. Analytical characteristics of the methods used were compared, and their reliability were tested against several certified reference materials of iron…concentrates. The relative standard deviation was less than 0.3%.