Journal of X-Ray Science and Technology - Volume 23, issue 4

Authors: Gong, Xuepeng | Lu, Qipeng

Article Type: Research Article

Abstract: A new monochromator is designed to develop a high performance soft X-ray microscopy beamline at Shanghai Synchrotron Radiation Facility (SSRF). But owing to its high resolving power and high accurate spectrum output, there exist many technical difficulties. In the paper presented, as two primary design targets for the monochromator, theoretical energy resolution and photon flux of the beamline are calculated. For wavelength scanning mechanism, primary factors affecting the rotary angle errors are presented, and the measuring results are 0.15'' and 0.17'' for plane mirror and plane grating, which means that it is possible to provide sufficient scanning precision to specific …wavelength. For plane grating switching mechanism, the repeatabilities of roll, yaw and pitch angles are 0.08'', 0.12'' and 0.05'', which can guarantee the high accurate switch of the plane grating effectively. After debugging, the repeatability of light spot drift reaches to 0.7'', which further improves the performance of the monochromator. The commissioning results show that the energy resolving power is higher than 10000 at Ar L-edge, the photon flux is higher than 1 × 108 photons/sec/200 mA, and the spatial resolution is better than 30 nm, demonstrating that the monochromator performs very well and reaches theoretical predictions. Show more

Keywords: Monochromator, soft X-ray microscopy beamline, STXM, plane grating

DOI: 10.3233/XST-150497

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 4, pp. 409-421, 2015

Authors: Qiao, Zhiwei | Redler, Gage | Epel, Boris | Qian, Yuhua | Halpern, Howard

Article Type: Research Article

Abstract: Electron paramagnetic resonance (EPR) Imaging (EPRI) is a robust method for measuring in vivo oxygen concentration (pO2 ). For 3D pulse EPRI, a commonly used reconstruction algorithm is the filtered backprojection (FBP) algorithm, in which the backprojection process is computationally intensive and may be time consuming when implemented on a CPU. A multistage implementation of the backprojection can be used for acceleration, however it is not flexible (requires equal linear angle projection distribution) and may still be time consuming. In this work, single-stage backprojection is implemented on a GPU (Graphics Processing Units) having 1152 cores to accelerate the process. …The GPU implementation results in acceleration by over a factor of 200 overall and by over a factor of 3500 if only the computing time is considered. Some important experiences regarding the implementation of GPU-accelerated backprojection for EPRI are summarized. The resulting accelerated image reconstruction is useful for real-time image reconstruction monitoring and other time sensitive applications. Show more

Keywords: GPU, acceleration, backprojection, EPR, EPR imaging

DOI: 10.3233/XST-150498

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 4, pp. 423-433, 2015

Authors: Karimi, Seemeen | Martz, Harry | Cosman, Pamela

Article Type: Research Article

Abstract: BACKGROUND: In aviation security, checked luggage is screened by computed tomography scanning. Metal objects in the bags create artifacts that degrade image quality. Though there exist metal artifact reduction (MAR) methods mainly in medical imaging literature, they require knowledge of the materials in the scan, or are outlier rejection methods. OBJECTIVE: To improve and evaluate a MAR method we previously introduced, that does not require knowledge of the materials in the scan, and gives good results on data with large quantities and different kinds of metal. METHODS: We describe in …detail an optimization which de-emphasizes metal projections and has a constraint for beam hardening and scatter. This method isolates and reduces artifacts in an intermediate image, which is then fed to a previously published sinogram replacement method. We evaluate the algorithm for luggage data containing multiple and large metal objects. We define measures of artifact reduction, and compare this method against others in MAR literature. RESULTS: Metal artifacts were reduced in our test images, even for multiple and large metal objects, without much loss of structure or resolution. CONCLUSION: Our MAR method outperforms the methods with which we compared it. Our approach does not make assumptions about image content, nor does it discard metal projections. Show more

Keywords: Metal artifacts, metal artifact reduction, computed tomography, luggage screening, constrained optimization

DOI: 10.3233/XST-150499

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 4, pp. 435-451, 2015

Authors: Elgebaly, Reem H. | Rageh, Monira M. | Adel, Mahmoud

Article Type: Research Article

Abstract: BACKGROUND: There are various physical factors that limit the quality of the Single Photon Emission Computed Tomography (SPECT) images such as number of frames per projection, number of projections per scan and time per projection in gated myocardial SPECT scan. OBJECTIVE: The aim of the present work was to evaluate physical acquisition parameters affecting the cardiac imaging to optimize the patient's examination time and image quality that are acquired with the gamma camera and workers radiation protection (through reducing time of radiation exposure) in cardiac SPECT facility. Cardiac functional parameters like ejection fraction (EF), end diastole …volume (EDV), end systole volume (ESV) and total perfusion defect (TPD) were evaluated. METHODS: Thirty patients were divided into three groups as follows: 1- Group (1): contains two sub-groups, one scanned with 8 frames per projection, the other with 16 frames per projection. 2- Group (2): contains two sub-groups, one scanned with 32 projections per scan, the other with 16 projections per scan. 3- Group (3): contains two sub-groups, one scanned at a time per projection of 20 s and the other scanned at 10 s per projection. Parameters such as the Ejection Fraction (EF), End Diastole Volume (EDV), End Systole Volume (ESV) and Total Perfusion Defect (TPD) in SPECT were compared for each group. RESULTS: There was insignificant difference in the EF, EDV, ESV and TPD between the different groups concerning the number of frames per projection, number of projections per scan and time per projection. CONCLUSION: The reduction of scan time to half or the number of projections per scan to half or increasing the number of frames per scan from 8 to 16 at the same duration has insignificant effect in the cardiac functional parameters used with gated SPECT scan. Show more

Keywords: Gated SPECT, physical acquisition parameters, filtered back projections (FBP), gamma camera

DOI: 10.3233/XST-150500

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 4, pp. 453-461, 2015

Authors: Zhang, Xuanxuan | Liu, Fei | Zuo, Siming | Bai, Jing | Luo, Jianwen

Article Type: Research Article

Abstract: The present full-angle, free-space fluorescence molecular tomography (FMT) system uses a step-by-step strategy to acquire measurements, which consumes time for both the rotation of the object and the integration of the charge-coupled device (CCD) camera. Completing the integration during the rotation is a more time-efficient strategy called synchronous data acquisition. However, the positions of sources and detectors in this strategy are not stationary, which is not taken into account in the conventional reconstruction algorithm. In this paper we propose a reconstruction algorithm based on the finite element method (FEM) to overcome this problem. Phantom experiments were carried out to validate …the performance of the algorithm. The results show that, compared with the conventional reconstruction algorithm used in the step-by-step data acquisition strategy, the proposed algorithm can reconstruct images with more accurate location data and lower relative errors when used with the synchronous data acquisition strategy. Show more

Keywords: Fluorescence, image reconstruction, synchronous data acquisition, tomography

DOI: 10.3233/XST-150501

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 4, pp. 463-472, 2015

Authors: Ryu, Jong-Hyun | Kim, Tae-Hoon | Jeong, Chang-Won | Jun, Hong-Young | Heo, Dong-Woon | Lee, Jinseok | Kim, Kyong-Woo | Yoon, Kwon-Ha

Article Type: Research Article

Abstract: BACKGROUND: Mobile computed tomography (CT) with a cone-beam source is increasingly used in the clinical field. Mobile cone-beam CT (CBCT) has great merits; however, its clinical utility for brain imaging has been limited due to problems including scan time and image quality. OBJECTIVE: The aim of this study was to develop a dedicated mobile volumetric CBCT for obtaining brain images, and to optimize the imaging protocol using a brain phantom. METHODS: The mobile volumetric CBCT system was evaluated with regards to scan time and image quality, measured as signal-to-noise-ratio (SNR), contrast-to-noise-ratio (CNR), …spatial resolution (10% MTF), and effective dose. Brain images were obtained using a CT phantom. RESULTS: The CT scan took 5.14 s at 360 projection views. SNR and CNR were 5.67 and 14.5 at 120 kV/10 mA. SNR and CNR values showed slight improvement as the x-ray voltage and current increased (p < 0.001). Effective dose and 10% MTF were 0.92 mSv and 360 μ m at 120 kV/10 mA. Various intracranial structures were clearly visible in the brain phantom images. CONCLUSIONS: Using this CBCT under optimal imaging acquisition conditions, it is possible to obtain human brain images with low radiation dose, reproducible image quality, and fast scan time. Show more

Keywords: Cone-beam computed tomography, volumetric computed tomography, dedicated mobile CT, brain imaging

DOI: 10.3233/XST-150502

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 4, pp. 473-480, 2015

Authors: Li, Xiaozhong | Liu, Taiyun | Wang, Lin

Article Type: Research Article

Abstract: OBJECTIVES: To study CT finding and the value of retrograde cystography CT scan in the diagnosis of bladder diverticulum. MATERIAL AND METHODS: The study was performed in accordance with the regulations of the local institutional review board and ethics committee. Written, informed consent was obtained from all patients before the examination and enrolment into the study. 70 patients with bladder diverticulum (mean age 62 years; range 43-78 years, 39 males and 31 females) were examined, including ultrasound, X-ray cystogram, plain scan CT, contrast enhanced CT, the retrograde cystogram CT, compared the accuracy of these examination …in diagnosis of bladder diverticulum and observed size, location, shape, opening of bladder diverticulum. Selection and diagnosis of all patients of enrolled into the study were confirmed by cystoscopy. But, this result was double-blind to the resident doctors for them examined and diagnosed. Three examination were selected for each patient, the first examination was random, the second was the plain scan CT, the third was the retrograde cystogram CT, all patients were must examined by the plain scan CT and retrograde cystogram CT. RESULTS: In 70 patients, 22 case were examined by ultrasonic, 15 cases were accurate diagnosed, 4 cases were examined by X-ray cystography, 3 cases were accurate diagnosed, 70 cases were examined by plain scan CT, 48 cases were accurate diagnosed, 17 cases were examined by contrast enhanced CT, 12 cases were accurate diagnosed, 70 cases were examined by retrograde cystography CT, 70 cases were accurate diagnosed, retrograde cystography CT well showed the size, location, shape, opening of the bladder diverticulum, while others examination showed these were poor. CONCLUSIONS: Retrograde cystography CT could accurately diagnose bladder diverticulum, clearly showed the size, location, shape and opening of bladder diverticulum, could provide accurate and detailed information for clinical, thus it is a simple, effective and economical method of the diagnosis of bladder diverticulum. Show more

Keywords: Cystography, bladder diverticulum, tomography, X-ray computer

DOI: 10.3233/XST-150503

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 4, pp. 481-487, 2015

Authors: Misawa, Masaki | Nitta, Naotaka | Shirasaki, Yoshio | Hayashi, Kazuhiko | Kosaka, Ryo | Hyodo, Koji | Numano, Tomokazu | Homma, Kazuhiro | Kuribayashi, Shota | Fujihara, Yuko | Hoshi, Kazuto

Article Type: Research Article

Abstract: BACKGROUND: Transmission and tomographic X-ray measurements are useful in assessing bone structures, but only a few studies have examined cartilage growth because of the poor contrast in conventional X-ray imaging. OBJECTIVE: In this study, we attempted to use the linear attenuation coefficient (LAC) as a metric of tissue-engineered cartilage development, which would be useful in high-throughput screening of cartilage products. METHODS: Assuming that the LAC is related to the amount of extracellular matrix (ECM) in terms of the density and its atomic components, we measured X-ray absorption through tissue-engineered cartilage constructs. Characteristic …X-ray beams from a molybdenum microfocus X-ray tube were employed to avoid beam hardening. The correlation of the LAC with mechanical properties was analyzed for verification. RESULTS: The LAC was higher for chondrocyte constructs and lower for fibroblast-dominant constructs and was consistent with the quantification of toluidine blue staining, which is a proof of ECM production. The LAC was positively correlated with the bending modulus but negatively correlated with the dynamic elastic modulus and stiffness, possibly because of the remaining scaffold. CONCLUSIONS: The LAC has the potential to be used as a metric of development of tissue-engineered cartilage. However, the calcified regions should be excluded from analysis to avoid decreasing the correlation between the LAC and the amount of ECM. Show more

Keywords: X-ray absorptiometry, characteristic X-ray, linear attenuation coefficient, tissue-engineered cartilage, extra-cellular matrix

DOI: 10.3233/XST-150504

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 4, pp. 489-502, 2015

Authors: Chuang, Ho-Chiao | Hsu, Hsiao-Yu | Nieh, Shu-Kan | Tien, Der-Chi

Article Type: Research Article

Abstract: The purpose of this study is to assess the feasibility of using the analytical technique of ultrasound images in combination with an auto tumor localization system. During respiration, the activity of breathing in and out causes organs displacement at the lower lobe of the lung, and the maximum displacement range happens in the Superior-Inferior (SI) direction. Therefore, in this study all the tumor positioning is in SI direction under respiratory compensation, in which the compensations are carried out to the organs at the lower lobe and adjacent to the lower lobe of lung. In this research, due to the …processes of ultrasound imaging generation, image analysis and signal transmission, when the captured respiratory signals are sent to auto tumor localization system, there was a signal time delay. The total delay time of the entire signal transmission process was 0.254 ± 0.023 seconds (with the lowest standard deviation) after implementing a series of analyses. To compensate for this signal delay time (0.254 ± 0.023 sec), a phase lead compensator (PLC) was designed and built into the auto tumor localization system. By analyzing the impact of the delay time and the respiratory waveforms under different frequencies on the phase lead compensator, an overall system delay time can be configured. Results showed as the respiratory frequency increased, variable value ``a'' and the subsequent gain ``k'' in the controller becomes larger. Moreover, value ``a'' and ``k'' increased as the system delay time increased when the respiratory frequency was fixed. The relationship of value ``a'' and ``k'' to the respiratory frequency can be obtained by using the curve fitting method to compensate for the respiratory motion for tumor localization. Through the comparison of the uncompensated signal and the compensated signal performed by the auto tumor localization system on the simulated respiratory signal, the feasibility of using ultrasound image analysis technology combined with the developed auto tumor localization system can be evaluated. The results show that the simulated respiratory signals under different frequencies of 0.5, 0.333, 0.25, 0.2 and 0.167 Hz with phase lead compensators were improved and stabilized. The compensation rate increased to the range of 7.04$∼ $18.82%, and the final compensation rate is about 97%. Therefore the auto tumor localization system combined with the ultrasound image analysis techniques is feasible. In this study, the developed ultrasound image analysis techniques combined into the auto tumor localization system has the following four advantages: (1) It is a non-invasive way (ultrasonic images) to monitor the entire compensating process of the active respiration instead of using a C-arm (invasive) to observe the organs motion. (2) During radiation therapy, the whole treatment process can be continuous, which can save the overall treatment time. (3) It is an independent system, which can be mounted onto any treatment couch. (4) Users can operate this system easily without the need of prior complicated training process. Show more

Keywords: Real-time tracking, compensated respiratory motion, ultrasound image tracking, phase lead compensator

DOI: 10.3233/XST-150505

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 4, pp. 503-516, 2015

Authors: Zhou, Zhongxing | Gao, Feng | Zhao, Huijuan | Zhang, Lixin | Ren, Liqiang | Li, Zheng | Ghani, Muhammad U. | Hao, Ting | Liu, Hong

Article Type: Research Article

Abstract: The modulation transfer function (MTF) of a radiographic system is often evaluated by measuring the system's edge spread function (ESF) using edge device. However, the numerical differentiation procedure of the traditional slanted edge method amplifies noises in the line spread function (LSF) and limits the accuracy of the MTF measurement at low frequencies. The purpose of this study is to improve the accuracy of low-frequency MTF measurement for digital x-ray imaging systems. An edge spread function (ESF) deconvolution technique was developed for MTF measurement based on the degradation model of slanted edge images. Specifically, symmetric oversampled ESFs were constructed by …subtracting a shifted version of the ESF from the original one. For validation, the proposed MTF technique was compared with conventional slanted edge method through computer simulations as well as experiments on two digital radiography systems. The simulation results show that the average errors of the proposed ESF deconvolution technique were 0.11% ± 0.09% and 0.23% ± 0.14%, and they outperformed the conventional edge method (0.64% ± 0.57% and 1.04% ± 0.82% respectively) at low-frequencies. On the experimental edge images, the proposed technique achieved better uncertainty performance than the conventional method. As a result, both computer simulation and experiments have demonstrated that the accuracy of MTF measurement at low frequencies can be improved by using the proposed ESF deconvolution technique. Show more

Keywords: Digital x-ray imaging, edge spread function, modulation transfer function, deconvolution

DOI: 10.3233/XST-150506

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 4, pp. 517-529, 2015