Journal of X-Ray Science and Technology - Volume 17, issue 3

Authors: Xia, Dan | Cho, Seungryong | Pan, Xiaochuan

Article Type: Research Article

Abstract: Non-circular scanning geometries such as helix or circular sinusoid have been used or proposed for cone-beam computed tomography (CBCT), because they provide sufficient data for numerically stable and exact image reconstruction within the scanned volume. Analytic algorithms have been developed for image reconstruction from cone-beam data acquired with a full-scan circular sinusoidal trajectory. In this work, we propose an innovative imaging approach in which a reduced-scan circular sinusoidal trajectory is used for …acquiring data sufficient for exact 3D image reconstruction. A filtered backprojection (FBP) algorithm based on Pack-Noo's reconstruction formula is applied for image reconstruction in reduced-scan circular sinusoidal scans. We have conducted numerical studies to demonstrate the reduced-scan approach and to validate the FBP reconstruction algorithm in the proposed approach. The proposed scanning method can contribute to increasing the throughput of a scanner, while improving the image quality compared to a conventional circular scan. Show more

Keywords: Reduced-scan, circular sinusoidal trajectory, cone-beam, computed tomography

DOI: 10.3233/XST-2009-0222

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 3, pp. 189-205, 2009

Authors: Shen, Kuan | Wen, Yumei | Cai, Yufang

Article Type: Research Article

Abstract: Multiresolution Analysis (MRA) plays an important role in image and signal processing fields, and it can extract information at different scales. Image fusion is a process of combining two or more images into an image, which extracts features from source images and provides more information than one image. The research presented in this article is aimed at the development of an automated imaging enhancement system in digital radiography (DR) images, which can clearly display all the …defects in one image and don't bring blocking effect. In terms of characteristic of the collected radiographic signals, in the proposed scheme the subsection of signals is mapped to 0–255 gray scale to form several gray images and then these images are fused to form a new enhanced image. This article focuses on comparing the discriminating power of several multiresolution images decomposing methods using contrast pyramid, wavelet, and ridgelet respectively. The algorithms are extensively tested and the results are compared with standard image enhancement algorithms. Tests indicate that the fused images present a more detailed representation of the x-ray image. Detection, recognition, and search tasks may therefore benefit from this. Show more

Keywords: DR image, multiresolution analysis, contrast pyramid, wavelet transform, ridgelet transform, image fusion, image enhancement

DOI: 10.3233/XST-2009-0223

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 3, pp. 207-220, 2009

Authors: Liu, Baodong | Zeng, Li

Article Type: Research Article

Abstract: Linear scan cone-beam Computed Tomography (CT) is useful to fixed pipeline inspection. We extend Simultaneous Algebraic Reconstruction Technique (SART) to linear scan cone-beam CT and focus on reducing its reconstruction time through cluster computing. In order to reduce communication overhead, we investigate a trapeziform image space decomposition scheme and a subsets-reduce communication technique. The performance of proposed parallel algorithm is analyzed theoretically and verified through experiment. The results show that the …proposed parallel algorithm can generate approving CT images and its performance is mainly influenced by load imbalance and network bandwidth. Show more

Keywords: CT, linear scan, SART, cluster computing

DOI: 10.3233/XST-2009-0224

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 3, pp. 221-232, 2009

Authors: Zou, Xiaobing | Zeng, Li | Li, Zongjian

Article Type: Research Article

Abstract: In cone beam industrial computed tomography (ICT), it is often required to inspect the large object using flat detector. If traditional helical scanning is used, the field of view (FOV) is limited due to the size of flat detector. As an alternative, a dual helical cone-beam scanning is proposed in this paper. Before each helical scanning, x-ray source and flat detector are horizontally translated a given distance, and part of the object is covered by x-ray …at each view angle. Then the object function is reconstructed by use of the improved helical FDK algorithm, which does not rebin projection data. Simulations validate that the images, which are reconstructed by proposed scanning mode and improved algorithm with small flat detector, are similar to those from the conventional helical scanning and FDK algorithm with large flat detector. The improved FDK algorithm is not sensitive to translation step. Furthermore, the proposed scanning mode can extend the radius of FOV up to at least 1.7 times. Show more

Keywords: ICT, large object, dual helix, cone beam, improved FDK algorithm

DOI: 10.3233/XST-2009-0225

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 3, pp. 233-251, 2009

Authors: Brunetti, A. | Albertini, V. Rossi | Bailo, D.

Article Type: Research Article

Abstract: In Energy Dispersive X-Ray diffraction measurements, the estimate of momentum transfer q, on which the diffracted intensity depends, should be as accurate as possible. Since q, in turn, depends on both the energy and the scattering angle, an error on the latter due to an incorrect positioning of the sample, to the asymmetric angular spread induced by the collimation slits or, in general, to any uncertainty on the geometric setup, results in an uncertainty on the …q value. Here, a new self calibration method to correct such errors, based on a genetic algorithm is presented. It is robust, fast and completely automatic. Results obtained by carrying out Energy Dispersive X-Ray Diffraction measurements on reference samples are reported and discussed. They show how the application of such genetic algorithm may provide a fast esteem of the two parameters required when multiple angle pattern collection is performed, namely the effective starting angle and the angular step. In this way, reliable q-values of all the diffraction pattern features (Bragg peaks for crystalline, and diffused bumps for non-crystalline samples) are obtained. Show more

Keywords: GA, EDXRD, Bragg peaks

DOI: 10.3233/XST-2009-0226

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 3, pp. 253-264, 2009

Authors: Yin, Shaohui | Ohmori, Hitoshi | Liu, Qing | Morita, Shinnya | Chen, Fengjun | Asami, Muneaki | Fan, Yufeng

Article Type: Research Article

Abstract: An ultra-precision ELID grinding of large stamping dies of Wolter mirror for X-ray telescope was presented in this paper. The large stamping dies (S55C) with confocal paraboloid and hyperboloid was ground by ELID arc-enveloped grinding. In this ELID grinding system, cast iron fiber bonded (CIFB) diamond wheels were controlled by 3-dimentional ways to scan the work-piece and generate required surfaces. Its grinding characteristics such as attainable form accuracy, surface roughness were investigated. Furthermore, …some measures to improve form accuracy were discussed and verified such as truing, compensating, and on-machine measuring. Show more

Keywords: ELID grinding, large stamping die, Wolter mirror, arc-enveloped grinding, form accuracy, surface roughness

DOI: 10.3233/XST-2009-0227

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 3, pp. 265-277, 2009