Journal of X-Ray Science and Technology - Volume 9, issue 3-4

Authors: Jiang, Hangyi | Chen, Wei R. | Liu, Hong

Article Type: Research Article

Abstract: Full-field digital mammography imaging systems have been investigated extensively. However, most investigations focus on the quality assessment of the entire image. In this article, we present the results of experimental measurements on the position-dependent image characteristics of a CCD array-based digital imaging system. Objective image quality parameters such as noise power spectrum (NPS) and signal-to-noise ratio (SNR), which are also frequency-dependent, are employed for this investigation. The image detector uses 12 CCDs …arranged in a 4 × 3 array to cover a field of 18 cm × 24 cm with a single x-ray exposure. Totally 18 sub-areas were chosen as the regions-of-interest (ROIs) for each full-field image to study position-dependent characteristics. Our experimental results indicate that the image quality at different positions of the full-field image exhibit slightly variance due to the characteristic diversity of the CCDs and due to the oblique angle of the ROIs to the x-ray source. The image seams caused by the physical gaps between adjacent CCDs do not increase the noise components significantly to the composite full-field image. The x-ray energy-dependence of NPS and SNR was also studied. Show more

Keywords: noise power spectra, modulation transfer function, image quality, digital radiography, full-field mammography systems, signal-to-noise ratio

Citation: Journal of X-Ray Science and Technology, vol. 9, no. 3-4, pp. 101-111, 2001

Authors: Wang, Ben | Liu, Hong | Zhao, Shiying | Wang, Ge

Article Type: Research Article

Abstract: The cone-beam approach for image reconstruction attracts an increasing attention in various applications, especially medical imaging. Previously, the traditional practical cone-beam reconstruction method, the Feldkamp algorithm, was generalized into the case of spiral/helical scanning loci with equispatial cone-beam projection data. In this paper, we formulated the generalized Feldkamp algorithm in the case of equiangular cone-beam projection data, and performed numerical simulation to evaluate the image quality. Because medical multi-slice/cone-beam CT scanners typically …use equiangular projection data, our new formula may be useful in this area as a framework for further refinement and a benchmark for comparison. Show more

Keywords: computed tomography (CT), cone-beam geometry, Feldkamp-type reconstruction, medical imaging

Citation: Journal of X-Ray Science and Technology, vol. 9, no. 3-4, pp. 113-120, 2001

Authors: McNally, Patrick J. | Dilliway, G. | Bonar, J.M. | Willoughby, A. | Tuomi, T. | Rantamäki, R. | Danilewsky, A.N. | Lowney, D.

Article Type: Research Article

Abstract: Synchrotron X-Ray Topography has been used in Total Reflection Topography (TRT) mode to observe strain induced surface bumps due to the presence of underlying misfit dislocations in strained layer SiGe on Si epitaxial heterostructures. In these experiments the x-rays approached the sample surfaces at grazing incident angles below the total external reflection critical angles for a number of reflections and hence surface strain features nominally less than a few tens of Ångstroms from the sample surface …have been observed. These are similar to the surface bumpiness observed by Atomic Force Microscopy, albeit on a much larger lateral length scale. The fact that TRT mode images were taken was confirmed by the observation of clear and conventional back reflection topographic images of misfit dislocations in all samples when the grazing incidence angle became greater than the critical angle. Show more

Keywords: x-ray topography, total reflection, SiGe, misfit dislocations, epitaxy, strain

Citation: Journal of X-Ray Science and Technology, vol. 9, no. 3-4, pp. 121-130, 2001

Authors: Pardo, B. | André, J.-M.

Article Type: Research Article

Abstract: When a charged particle crosses an interface between two different materials, electromagnetic radiation called Transition Radiation is emitted. The spectrum of this radiation extends up to x-ray domain. The Resonant Transition Radiation (R.T.R.) can be observed with a periodic arrangement of interfaces. The R.T.R. in the soft x-ray range has been recently measured by K. Yamada and coll. with a Nickel-Carbon multilayer structure [1]. In this paper, a rigorous electromagnetic theory of the R.T.R in finite …and infinite multilayer structures is developed using the matricial formalism and compared with the experimental quoted data [1]. Show more

Citation: Journal of X-Ray Science and Technology, vol. 9, no. 3-4, pp. 131-145, 2001