Journal of X-Ray Science and Technology - Volume 20, issue 1

Authors: Fedrigo, Mattia | Wenger, Andreas | Hoeschen, Christoph

Article Type: Research Article

Abstract: A novel strategy to perform tomographic image reconstruction is presented, based on the integration of a priori information about the target image. Such information may come from a different imaging tool or a synthetic model. For a given image quality, providing a priori image information reduces the amount of image information to be reconstructed. According to the data processing inequality this requires less input data or physical measurements, therefore reducing exposure to ionising radiation. A …prototype algorithm is described, consisting of a penalized ART where some a priori edge information is encoded in an inhomogeneous, anisotropic smoothing kernel. The algorithm is tested on a 2-dimensional set-up based on the Shepp-Logan phantom. Show more

Keywords: Tomographic reconstruction, a priori information, edge detection, algebraic reconstruction method, complexity penalization

DOI: 10.3233/XST-2012-0314

Citation: Journal of X-Ray Science and Technology, vol. 20, no. 1, pp. 1-10, 2012

Authors: Lu, Xiongbing | Wu, Rongpei | Huang, Xiaoning | Zhang, Yuanyuan

Article Type: Research Article

Abstract: Noncontrast computed tomography (CT) has great advantage with higher sensitivity and more clear modalities in detecting urinary tract radiolucent calculi in patients with acute renal insufficiency (ARI) compared to other image diagnosis approaches. We report two cases (female, 28 years old; male, 39 years old) with persistent flank pain and acute anuria after the administration of ceftriaxone (4.0 g daily) for 2 days intravenously. No abnormality was found in the kidney-ureter- bladder (KUB) areas with plain …abdomen X-rays. A diagnosis of bilateral hydronephrosis was made by ultrasound examination in both cases. Serum creatinine levels reached up to 257 and 810 μ mol/L (normal serum creatinine level is 40–130 μ mol/L), respectively. Vague density spots were noticed in the pelvis with noncontrast multidetector-row CT (MDCT) scanning. However, distinguishable clusters of high-density shadows were seen in pelvic areas with maximum intensity projections (MIP, CT values in 30–128 HU). Ceftriaxone crystal calculi were found on both sides of distal ureters under endoscopy. Renal function recovered in both patients after double-J ureteral stents were installed. Out results demonstrated that noncontrast MDCT scanning and MIP reconstruction as an effective diagnostic tool could provide clear images in detection of radiolucent calculi in urinary tract when conventional X-rays image are not suitable in the patients with obstructive anuria and ARI of unknown origin. Show more

Keywords: Computed tomography (CT), maximum intensity projections (MIP), calculi, ureteral obstruction, acute renal insufficiency (ARI), urinary tract (UT), radiolucent calculi

DOI: 10.3233/XST-2012-0315

Citation: Journal of X-Ray Science and Technology, vol. 20, no. 1, pp. 11-16, 2012

Authors: Miao, Hui | Wu, Xizeng | Zhao, Huijuan | Liu, Hong

Article Type: Research Article

Abstract: Objective: The purpose of this study was to develop a phantom-based experimental calibration method to minimize the reconstruction artifacts for the geometric misalignments of the digital tomosynthesis prototype. Methods: A calibration phantom with ten fiducial markers was designed. Using this calibration phantom, the projection matrices of an experimental digital tomosynthesis prototype were acquired from each projection view under a series of misalignment conditions. The American College of Radiology mammography phantom was imaged and reconstructed …with and without using the correction of the corresponding calibration projection matrices. The effectiveness of the calibration technique was then quantitatively analyzed through comparison of the calibrated and uncalibrated images. Results: As the isocenter horizontal-shift increases, the reconstruction artifacts become clearly distinguishable. Using the calibration technique, the reconstruction artifacts resulting from the isocenter horizontal-shift were effectively minimized for the prototype. Conclusions: For the specific experimental conditions utilized in this study, the phantom-based calibration method effectively reduced reconstruction artifacts for the prototype investigated in this study. The calibration method holds potential to benefit other tomosynthesis applications. Show more

Keywords: Digital tomosynthesis, calibration, projection matrix, calibration phantom

DOI: 10.3233/XST-2012-0316

Citation: Journal of X-Ray Science and Technology, vol. 20, no. 1, pp. 17-29, 2012

Authors: Chen, Xueli | Liang, Jimin | Qu, Xiaochao | Hou, Yanbin | Zhu, Shouping | Chen, Duofang | Gao, Xinbo | Tian, Jie

Article Type: Research Article

Abstract: We present a method for mapping the two-dimensional (2D) bioluminescent images (BLIs) onto a three-dimensional (3D) body surface derived from the computed tomography (CT) volume data. This mapping includes two closely-related steps, the spatial registration of the 2D BLIs into the coordinate system of the CT volume data and the light flux recovering on the body surface from BLIs. By labeling markers on the body surface, we proposed an effective registration method to achieve the spatial …position alignment. The subsequent light flux recovering is presented based on the inverse process of the free-space light transport model and taking the influence of the camera lens diaphragm into account. Incorporating the mapping procedure into the bioluminescence tomography (BLT) reconstruction, we developed a dual-modality BLT and CT imaging framework to provide both optical and anatomical information. The accuracy of the registration and the light flux recovering methods were evaluated via physical phantom experiments. The registration method was found to have a mean error of 0.41 mm and 0.35 mm in horizontal and vertical direction, and the accuracy of the light flux recovering method was below 5%. Furthermore, we evaluated the performance of the dual-modality BLT/CT imaging framework using a mouse phantom. Preliminary results revealed the potential and feasibility of the dual-modality imaging framework. Show more

Keywords: Dual-modality imaging, bioluminescence tomography (BLT), computed tomography (CT), spatial registration, light flux recovering

DOI: 10.3233/XST-2012-0317

Citation: Journal of X-Ray Science and Technology, vol. 20, no. 1, pp. 31-44, 2012

Authors: Tang, Shaojie | Xu, Qiong | Mou, Xuanqin | Tang, Xiangyang

Article Type: Research Article

Abstract: In this paper, we discuss the mathematical equivalence among four consistency conditions in the divergent-beam computed tomography (CT). The first is the consistency condition derived by Levine et al. by degenerating the John's equation; the second is the integral invariant derived by Wei et al. using the symmetric group theory; the third is the so-called parallel-fan-beam Hilbert projection equality derived by Hamaker et al.; and the fourth is the fan-beam data consistency condition (FDCC) derived …by Chen et al. using the complex analysis theory. Historically, most of these consistency conditions were derived by their corresponding authors using complicated mathematical strategies, which are usually not easy to be precisely understood by researchers with only a general engineering mathematical background. In this paper, we symmetrically re-derive all these consistency conditions using a friendly mathematical language. Based on theoretical derivation, it has been found that all these consistency conditions can be viewed as a necessary condition for the specific solution to John's equation. From the physical point of view, all these consistency conditions have been essentially expressed as a similar constraint on the projection data acquired with arbitrary two x-ray source points. Numerical simulations have been carried out to experimentally evaluate and verify their merits. Show more

Keywords: Computed tomography, consistency condition, John's equation, mathematical equivalence

DOI: 10.3233/XST-2012-0318

Citation: Journal of X-Ray Science and Technology, vol. 20, no. 1, pp. 45-68, 2012

Authors: Wang, Xianchao | Li, Lei | Yu, Chaoqun | Yan, Bin | Bao, Shanglian

Article Type: Research Article

Abstract: In circular cone-beam computed tomography (CT), although the minimum data filtered-backprojection (MD-FBP) algorithm has many significant applications, such as handling super-short scan problem, its reconstruction efficiency is limited by the heavy calculation of backprojection. In this paper, aiming at the image reconstruction of flat region in a super-short scan, an improved method based on MD-FBP algorithm is developed using an integral operation with fixed integral interval during the implementation of backprojection, which …has an improvement in reconstruction efficiency and parallel performance compared with the original MD-FBP algorithm. It is found that if the thickness of the flat region is less than 0.0349 R (R is the scanning radius), the uncertainty of the method can be ignored. When the thickness of reconstructed region is a little fat, it can also be reconstructed by increasing the scanning radius befittingly. The results of numerical simulation and real data experiments have demonstrated the correctness and merits of the proposed method. Show more

Keywords: Computed tomography, image reconstruction, PI-line, super-short scan, MD-FBP algorithm

DOI: 10.3233/XST-2012-0319

Citation: Journal of X-Ray Science and Technology, vol. 20, no. 1, pp. 69-77, 2012

Authors: Demir, Demet | Şahin, Yusuf

Article Type: Research Article

Abstract: The effect of the external magnetic field has been investigated on the Ll, Lα, Lβ and Lγ production cross sections of Pt and Au elements in the angular range 90°–150° by using an energy dispersive x-ray fluorescence spectrometer. The samples were irradiated by using the gamma rays of 59.537 keV emitted from an ^{241} Am radioisotope source of 100 mCi. The external magnetic fields have been applied two opposite directions and …the magnitude of the external magnetic field has been fixed at +0.75 T and −0.75 T. For B=0, Ll and Lα groups in the L x-ray lines are found to be spatially anisotropic, while those in the Lβ and Lγ peaks are isotropic. An enhancement in the differential Ll and Lα production cross sections is observed in the presence of external magnetic field. Integral cross sections for production of Ll, Lα, Lβ and Lγ x-rays were also deduced and were found to be in good agreement with the theoretical values for B=0. Show more

Keywords: Angular dependence, x-ray production cross section, external magnetic field

DOI: 10.3233/XST-2012-0320

Citation: Journal of X-Ray Science and Technology, vol. 20, no. 1, pp. 79-89, 2012

Authors: Gao, Feng | Li, Jiao | Zhang, Wei | Yi, Xi | Wang, Xin | Zhang, Limin | Zhou, Zhongxing | Zhao, Huijuan

Article Type: Research Article

Abstract: A fiber-based non-contact scheme of the time-domain diffuse fluorescence yield and lifetime tomography is described that combines the time-correlated single photon counting technique for high-sensitive, time-resolved detection and CT-analogous configuration for large data-set collection. A pilot validation of the methodology is performed for two-dimensional scenarios using simulated and experimental data. The results demonstrated the efficacy of the proposed scheme in improving the image quality.

Keywords: Diffuse fluorescence tomography, time-resolved detection, CT-scanning configuration, image reconstruction technique, photon migration

DOI: 10.3233/XST-2012-0321

Citation: Journal of X-Ray Science and Technology, vol. 20, no. 1, pp. 91-105, 2012

Authors: Liu, Jiangkun | Ning, Ruola | Cai, Weixing | Benitez, Ricardo Betancourt

Article Type: Research Article

Abstract: Cone Beam Breast CT is a promising diagnostic modality in breast imaging. Its isotropic 3D spatial resolution enhances the characterization of micro-calcifications in breasts that might not be easily distinguishable in mammography. However, due to dose level considerations, it is beneficial to further enhance the visualization of calcifications in Cone Beam Breast CT images that might be masked by noise. In this work, the Papoulis-Gerchberg method was modified and implemented in Cone Beam Breast CT images …to improve the visualization and detectability of calcifications. First, the PG method was modified and applied to the projections acquired during the scanning process; its effects on the reconstructed images were analyzed by measuring the Modulation Transfer Function and the Noise Power Spectrum. Second, Cone Beam Breast CT images acquired at different dose levels were pre-processed using this technique to enhance the visualization of calcification. Finally, a computer-aided diagnostic algorithm was utilized to evaluate the efficacy of this method to improve calcification detectability. The results demonstrated that this technique can effectively improve image quality by improving the Modulation Transfer Function with a minor increase in noise level. Consequently, the visualization and detectability of calcifications were improved in Cone Beam Breast CT images. This technique was also proved to be useful in reducing the x-ray dose without degrading visualization and detectability of calcifications. Show more

Keywords: Cone beam breast CT, PG method, breast calcifications, spatial resolution

DOI: 10.3233/XST-2012-0322

Citation: Journal of X-Ray Science and Technology, vol. 20, no. 1, pp. 107-120, 2012

Authors: Gao, Yong | Xu, Ming | Xu, Zuo-Feng | Liu, Da-Wei | Tu, Xiang-An | Zheng, Yan-Ling | Wang, Dao-Hu | Sun, Xiang-Zhou | Zheng, Fu-Fu | Qiu, Shao-Peng | Lü, Ming-De | Zhang, Yuan-Yuan | Xie, Xiao-Yan | Deng, Chun-Hua

Article Type: Research Article

Abstract: Percutaneous ultrasound-guided radiofrequency ablation is increasingly being studied in the treatment of renal tumors. Because percutaneous ultrasound-guided radiofrequency ablation is a minimally invasive and nephron-sparing procedure, it is ideally suited for patients with a single kidney, multiple tumors, or contraindications to conventional surgery. We report on a patient with Von Hippel-Lindau (VHL) disease who had multicentric tumors in the single kidney that was successfully treated with percutaneous ultrasound-guided radiofrequncy ablation. The one-year …follow-up showed that there was no local recurrence or metastasis. And genetic testing showed the patient had a T to G heterozygotic missense mutation at nucleotide 515 of VHL gene exon 1. Show more

Keywords: Percutaneous ultrasound-guided radiofrequncy ablation, genetic analyses, renal cell carcinoma, Von Hippel-Lindau disease

DOI: 10.3233/XST-2012-0323

Citation: Journal of X-Ray Science and Technology, vol. 20, no. 1, pp. 121-129, 2012