Journal of X-Ray Science and Technology - Volume 16, issue 3

Authors: Koyuncu, Baki | Akdogan, Umran Funda

Article Type: Research Article

Abstract: The facial expressions of an human being can be explained by the motion of the facial features. If we are able to define these expressions by some motion vectors it will be possible to reconstruct the original face image from the face image with expression. In this context, the studies of this paper are focussed around the motion vector estimation and image reconstruction. For the motion vector estimation two well-known block matching techniques, namely Full Search …Algorithm and Three Step Search Algorithm, have been used and the results have been compared via PSNRs (Peak-to-Peak Signal-to-Noise Ratio) and time consumptions. Show more

Keywords: Motion vector estimation, facial expression, block matching techniques, full search, three step search

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 3, pp. 159-169, 2008

Authors: Zeng, Kai | Fajardo, Laurie L. | Kao, Simon | Franken, Edmund A. | Park, Jeong Mi | Jing, Zhenxue | Bai, Er-wei | Wang, Ge

Article Type: Research Article

Abstract: Tomosynthesis was developed for mammography, especially breast cancer detection. However, its limited-angular range scan and resultant data incompleteness causes strong image artifacts and distortions. To address this problem, a hybrid imaging method was proposed in our previous work, which combines tomosynthesis and low-resolution CT into a single system to produce fewer artifacts and distortions at a similar dose level. The purpose of this paper is to evaluate the images reconstructed using the proposed method as …compared with that using the conventional tomosynthesis method (ML-convex). For that purpose, the projection datasets are acquired in both numerical simulation and phantom experiments on our breast imaging platform. Three kinds of phantoms are used in our work, including a numerical phantom, a physical phantom and 8 in vitro phantoms made of breast specimens. In addition to visual comparison of the reconstructed images, we employ spatial resolution, image contrast, reconstruction error, and convergence rate to evaluate the results quantitatively. It is observed that the results from our method can achieve significantly higher spatial resolution, higher contrast, smaller reconstruction error and faster convergence rate. Besides, a reader study using 8 in vitro phantoms of breast specimens demonstrates the clinical potential of our method, which significantly outperforms the conventional tomosynthesis. Show more

Keywords: Cone-beam CT, tomosynthesis, mammography, breast imaging, image quality

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 3, pp. 171-187, 2008

Authors: Chen, Jian | Tian, Jie | Tang, Zichun | Xue, Jian | Dai, Yakang | Zheng, Jian

Article Type: Research Article

Abstract: In order to extract the low contrast vessels in retinal images, we propose a novel enhancement algorithm based on directional field and develop a robust retinal vessel extraction framework. The proposed enhancement algorithm can significantly improve the contrast of vasculature especially the slim vessels and low contrast vessels. In our framework, we first enhance the vasculature by the proposed enhancement algorithm, and extract the vessels from the enhanced image by a local extraction method. Secondly, we …apply a series of modified top-hat transform to original image, and use a binary morphological reconstruction to extract the large size vessels. Finally, the whole vasculature is provided by an organic combination algorithm. The first step extracts the slim vessels and low contrast vessels well but misses some bifurcations and cross pixels. On the other hand, the second step preserves the bifurcations and cross pixels but misses some slim vessels and low contrast vessels. Therefore, the combination of the two methods can provide satisfactory extraction of vasculature. Experimental results show that our method outperforms existing algorithms in terms of sensitivity and accuracy when testing on 'DRIVE' and 'STARE' databases. Show more

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 3, pp. 189-201, 2008

Authors: Khalatbari, Azadeh | Jenab, Kouroush

Article Type: Research Article

Abstract: In this paper, we study the reliability of X-ray imaging diagnosis considering human cognitive abilities (e.g., spatial orientation, visualization, line orientation, and perceptual speed), which play a vital role in the clinical decision making that requires classification systems. Also, this study explores sex influence on X-ray imaging diagnosis based on 176 X-ray images evaluated by 10 female radiologists and 8 male radiologists. Most related literature focuses on a binary classification (True or False) that uses …a set of features derived from a given pattern. Also, they utilize the Receiver Operating Characteristics (ROC) analyses for assessing the accuracy of X-ray diagnosis. In this study, we use fuzzy benchmarking to construct fuzzy classification systems required for fuzzy medical decision-making and fuzzy reliability assessment. The proposed method differentiates the influence of human cognitive abilities and sex in X-ray diagnosis. The results from this study shows reliability of X-ray diagnosis is high and male radiologists excel in spatial and line orientation and female radiologists perform better in perceptual speed while both are competent in visualization ability. Show more

Keywords: X-ray diagnosis, diagnosis reliability, radiology, human cognitive, decision-making, ROC, human errors

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 3, pp. 203-213, 2008

Authors: Lankinen, A. | Svensk, O. | Mattila, M. | Tuomi, T.O. | Lipsanen, H. | McNally, P.J. | O'Reilly, L. | Paulmann, C.

Article Type: Research Article

Abstract: X-ray excited optical luminescence (XEOL) measurements of Mg-doped GaN were made using continuous spectrum of synchrotron radiation. The samples were grown by metalorganic vapour phase epitaxy (MOVPE) on α-Al_{2} O_{3} substrates. The electrical activation of the Mg dopants by thermal annealing was detected in the room-temperature XEOL spectra, but not in the ultraviolet light excitation low-temperature photoluminescence (PL) spectra. The better results of the X-ray excitation over the ultraviolet …excitation PL is attributed to the larger penetration depth of X-rays in heavily Mg-doped GaN. The activation of the Mg dopants was confirmed using Hall measurements. Show more

Keywords: XEOL, PL, luminescence, synchrotron, X-ray, GaN, Mg

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 3, pp. 215-220, 2008

Authors: Zhou, Huaibei | Wang, Hui | Liu, Feng | Kong, Ruoshan

Article Type: Research Article

Citation: Journal of X-Ray Science and Technology, vol. 16, no. 3, pp. 221-224, 2008