Journal of X-Ray Science and Technology - Volume 14, issue 1

Authors: Fei, Chunguo | Han, Zhengzhi | Liu, Qingkun

Article Type: Research Article

Abstract: The flaw classification has become one of important tasks in evaluating the seafloor petroleum transporting pipeline integrity. With the aim to classify different kinds of artificial flaws from ultrasonic signals, we develop a novel flaw classification system. In this system we employ wavelet packet decomposition (WPD) to extract the features of ultrasonic signals, employ a new optimization algorithm (chaotic genetic algorithm-CGA) to get rid of redundant and irrelevant features, and employ support vector machine (SVM) …classifier to classify the flaws. We use a 5 MHz focal wideband transducer to test four kinds of artificial flaws and collect ultrasonic signals at a 40 MHz sampling rate by a high speed A/D card. Noise cancellation is implemented by adaptive filtering. For comparison purpose, we use different methods as feature selector. Then we compare their results. Through experiment, we can conclude that our system can improve the performance of the SVM classifier for flaws in seafloor pipeline significantly. Show more

Keywords: Ultrasonic inspecting, feature selection, chaotic genetic algorithm (CGA), support vector machine (SVM), wavelet packet decomposition (WPD)

Citation: Journal of X-Ray Science and Technology, vol. 14, no. 1, pp. 1-9, 2006

Authors: Gu, Jian-wei | Zhang, Li | Chen, Zhi-qiang | Xing, Yu-xiang | Huang, Zhi-feng

Article Type: Research Article

Abstract: X-ray CT plays a great role both in medical fields and in industrial nondestructive tests. In imaging, metal objects absorb X-rays greatly, which introduces streaks on reconstructed images. In this paper, we propose a method for metal artifacts reduction. Firstly, the metal projection region is accurately identified and an interpolation method based on such identification is applied to get the projection data without metal. The image excluding metal is reconstructed from the modified projection data. Secondly, …the image without metal is combined with the image of metal to form a complete reconstruction. Numerical simulations and a phantom experiment demonstrate that the metal artifacts can be effectively suppressed using our method and the reconstructed image is more accurate in depicting the details of cross-sections, especially in the immediate neighborhood of the metal object. The proposed method is computationally efficient and can be easily adapted to current commercial CT scanners. Show more

Keywords: X-ray CT, metal artifacts reduction (MAR), interpolation method

Citation: Journal of X-Ray Science and Technology, vol. 14, no. 1, pp. 11-19, 2006

Authors: Liu, Qingkun | Que, Peiwen | Guo, Huawei | Song, Shoupeng

Article Type: Research Article

Abstract: This paper proposes a new denoising method for ultrasonic nondestructive evaluation (NDE) signals using reconstructed phase space (RPS) and independent component analysis (ICA). The proposed method consists of four steps. Firstly a RPS is constructed from the ultrasonic NDE signal. The information about the underlying sources (e.g. ultrasonic signal, noise etc.) acting on the ultrasonic NDE system is contained in this RPS. Second ICA is performed on the RPS to recover all the sources underlying the …RPS. Next the desired ultrasonic signal component is selected by decision criterion related to the denoising application and finally is reconstructed to obtain the denoised ultrasonic signal. To validate the proposed method it has been applied to the mixture of simulated ultrasonic NDE signals and Guassian White Noise (WGN). The simulation results show that the signal noise ratio (SNR) of the noise ultrasonic NDE signals can be enhanced greatly using the proposed method. Show more

Keywords: Ultrasonic testing, nondestructive evaluation (NDE), reconstructed phase space (RPS), independent component analysis (ICA)

Citation: Journal of X-Ray Science and Technology, vol. 14, no. 1, pp. 21-26, 2006

Authors: Bai, Er-Wei | Bennett, James R. | McCabe, Robert | Sharafuddin, Melhem J. | Bai, Henri | Halloran, John | Vannier, Michael | Liu, Ying | Wang, Chenglin | Wang, Ge

Article Type: Research Article

Abstract: To improve imaging quality and to reduce contrast dose and radiation exposure, an adaptive bolus chasing CT angiography was proposed so that the bolus peak position and the imaging aperture can be synchronized. The performance of the proposed adaptive bolus chasing CT angiography was experimentally evaluated based on the actual bolus dynamics. The experimental results show that the controlled table position and the bolus peak position were highly consistent. The results clearly demonstrate that the proposed …adaptive bolus chasing CT angiography that synchronizes the bolus peak position with the imaging aperture by a simple adaptive system is computationally and clinically feasible. Similar techniques may also be applied to conventional angiography to improve imaging quality and to reduce contrast dose and/or radiation exposure. Show more

Keywords: CT angiography, contrast studies, automatic control, nonlinear system

Citation: Journal of X-Ray Science and Technology, vol. 14, no. 1, pp. 27-38, 2006

Authors: Khoury, Naji | Zaman, Musharraf | Laguros, Joakim

Article Type: Research Article

Abstract: A laboratory study was undertaken to investigate the performance of limestone aggregate base stabilized with different stabilizing agents, namely, class C fly ash, cement kiln dust and fluidized bed ash. Cylindrical specimens were compacted and cured for 1 hour, 3 days and 28 days prior to tests of unconfined compressive strength (UCS), scanning electron microscopy, energy-dispersive spectrometry and X-ray diffraction. Results showed that the UCS values increased with curing time. It was also found that the …different stabilizing agents produced different UCS values. The reference intensity ratio (RIR) method was employed to identify and quantify the mass percent of minerals and cementing compounds in the mixtures. Results revealed the formation of cementing compounds such as ettringite, C-S-H, C-A-H and C-A-S-H, which were responsible for an increase in the UCS values. In this study, the sum of all the cementing compounds (SCC) showed the same beneficiation trend as the UCS trend with curing time. Finally, the UCS values correlated fairly well with SCC. The SEM micrographs showed the intensity of crystal formation and hydration coating, which increased with curing time and percentage of additive. Show more

Keywords: Cementitious stabilization, X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, unconfined compressive strength, reference intensity ratio

Citation: Journal of X-Ray Science and Technology, vol. 14, no. 1, pp. 39-54, 2006

Authors: Vogel, Abby | Gandjbakhche, Amir | Gannot, Israel

Article Type: Research Article

Abstract: This paper describes a few optical imaging methods in their translational stage to the clinical phase. The methods are compared to well-established X-ray imaging methods such as computed tomography and mammography. The drawback of the diffuse paths of laser photons compared to the ballistic paths of the X-ray is compensated by coherence methods for tissue characterization adjacent to the surface, and acoustic wave enhanced imaging and fluorescent markers that follow functional changes when deeper tissue is …analyzed. This paper presents some of the latest developments in this field as presented in a Bench to Bedside workshop on optical imaging held at the National Institutes of Health. Show more

Keywords: Optical imaging, optical coherence tomography, X-ray imaging, computed tomography, functional imaging

Citation: Journal of X-Ray Science and Technology, vol. 14, no. 1, pp. 55-72, 2006