Journal of X-Ray Science and Technology - Volume 16, issue 2

Authors: Zhang, Guowei | Cheng, Jianping | Zhang, Li | Chen, Zhiqiang | Xing, Yuxiang

Article Type: Research Article

Abstract: Quantitative imaging based on dual energy computed tomography (DECT) is useful in both medical and industrial areas. However, the dependence of the attenuation coefficient on X-ray energy and the polychromatic property of X-ray beams bring obstacles for dual energy image reconstruction. In this paper, attenuation coefficient function μ(E) is approximated with the basis material model. And X-ray spectra which govern the projection functions are estimated from transmission measurements. With these two foundations, …we obtain a practical reconstruction method for DECT. The distribution of effective atomic number, electron density, and linear attenuation coefficient at any desirable energy can be reconstructed using the proposed method. Numerical simulations and practical experiments were conducted to evaluate the accuracy and practicability of the method. Show more

Keywords: Dual energy computed tomography, basis material decomposition, spectrum estimation, effective atomic number

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 2, pp. 67-88, 2008

Authors: Saikia, Binoy K. | Boruah, Rajani K.

Article Type: Research Article

Abstract: Coal is one of the most abundant energy resources and has the capability to meet future energy needs with high reliability. The basic knowledge of coal structure is crucial to an understanding of the physical properties of coal and chemistry of conversion processes such as gasification, liquefaction, combustion and carbonization. Coal samples from Makum coalfield, Assam, India were investigated by X-ray diffraction techniques. The highly diffuse X-ray diffraction profiles indicate that the coals have amorphous …carbon in their structures. Some of the X-ray structural parameters were evaluated by a semi-quantitative method. The parameters determine were d_{002} , d_{10} , L_{a} and L_{c} of various carbon contents (wt%) of different collieries. Strong linear relationship of d_{002} with the wt% of carbon of the coals was observed. The present study reveals that the Assam coals consist of random layered structures with turbostratic carbons. Show more

Keywords: Indian coal, Assam coal, coal structure, random layered structure, X-ray scattering

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 2, pp. 89-94, 2008

Authors: Tang, Shaojie | Mou, Xuanqin | Yang, Ying | Xu, Qiong | Yu, Hengyong

Article Type: Research Article

Abstract: The polychromatic spectrum of photons emitted by an X-ray tube in medical diagnostic CT system brings beam hardening artifact. Although many correction methods have been developed, it is still the major artifact in clinical CT imaging. Motivated by CT reconstruction researches benefiting from mathematical phantoms, one so-called physical mathematical phantom and its projection simulation are presented in this paper, which are used in comprehensive evaluation of beam hardening corrections. Due to the inherent …merits as compared to discrete and stochastic simulations, an analytic method is proposed to simulate the polychromatic projections of FORBILD head phantom. Firstly, CT-numbers are mapped to material compositions under the precondition sub-regions represent different human tissues. Second, boundary parameters of sub-regions are determined by the presented algorithms. Finally, projections are calculated according to X-ray energy spectrum. For validating the usefulness of our simulation, several typical correction methods are analyzed using simulated projections. The performance of every correction is exhibited distinctly. The analysis results show that there are still the spaces to improve those correction methods. Show more

Keywords: Polychromatic spectrum, beam hardening, projection simulation, FORBILD

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 2, pp. 95-117, 2008

Authors: Cesareo, Roberto | Brunetti, Antonio

Article Type: Research Article

Abstract: A portable EDXRF equipment was employed to analyze pre-Columbian metals (gold, silver and copper objects) and to determine the thickness of gold in the case of gildings. To this aim, the EDXRF equipment was optimized to detect Cu, Au and Ag, and various methods were developed to determine from X-ray spectra (K-lines ratio) the thickness of the gildings. These methods were first tested to measure gilding compositions and thicknesses of pens and decorative objects. Then pre-Columbian …metals were analyzed, such as gold, silver, copper, gilded copper and gilded silver objects from the Royal Tomb of Sipán and from the Museum of Sicán, in the north of Peru. Show more

Keywords: X-ray fluorescence, portable equipment, ratio of K-lines, gilded objects, silvered objects, Sipán alloys, Sicán alloys

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 2, pp. 119-130, 2008

Authors: Sun, Lei | Wang, Xiao-Ping | Chen, Tong-Sheng | Wang, Long-Xiang

Article Type: Research Article

Abstract: Chan-Su (CS), a traditional Chinese medicine, is one of the most potent Chinese medicines currently used in cancer chemoprevention and treatment. However, the molecular mechanism of CS-induced-apoptosis is still unclear. This study investigated the molecular mechanism of CS-induced apoptosis using fluorescence resonance energy transfer (FRET) and confocal fluorescence microscope techniques. CS dose-dependently inhibited cell viability cytotoxicity, which was assayed by Cell Counting Kit (CCK-8) and Hoechst33258 staining. Bax translocation to mitochondria was …observed in single living cell transfected with GFP-Bax plasmid. The mitochondrial membrane potential (ΔΨ_{m} ) loss was also measured in CS-treated cells. And ASTC-a-1 cell expressed stably with SCAT3 plasmid was used to examine if caspase-3 was activated by CS. z-VAD-fmk, a broad-caspase spectrum inhibitor, was found to significantly reduce the inhibition of CS on the cell viability. Overall, our data demonstrated that CS induced ASTC-a-1cells apoptosis in a dose-dependent manner, and Bax, caspase-3 and mitochondrial stress were involved in CS-induced apoptosis. Our findings extend the knowledge about the cellular signaling mechanisms mediating CS-induced apoptosis. Show more

Keywords: Chan-Su (CS), Bax translocation, apoptosis, caspase-3, fluorescence resonance energy transfer (FRET), mitochondrial membrane potential (ΔΨ_{m})

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 2, pp. 131-142, 2008

Authors: Zhang, Yan | Ning, Ruola

Article Type: Research Article

Abstract: Cone beam CT (CBCT) imaging technique has found many applications in medical imaging in recent years since it provides three-dimensional image reconstruction with low contrast detectability and high resolution. In CBCT systems, image noise caused by photon counting statistics plays an important role in image quality by affecting low contrast detection and patient dose. In this paper, we studied image noise caused by photon counting statistics with the Feldkamp's cone beam reconstruction algorithm. A noise model …based on photon counting detector was developed to provide the noise distribution in 3D image space and the quantitative relationships between image noise level and various CT parameters, including the exposure level, the number of projections, the reconstruction filter and the detector pixel size. Computer simulations of a spherical water phantom were conducted to test the theoretical model. This work provides the noise spatial distribution in cone-beam CT and its relationship with CBCT parameters. It can also provide local noise information for adaptive de-noising in the future. Show more

Keywords: Image noise, photon counting, statistics, noise distribution, cone-beam CT

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 2, pp. 143-158, 2008