Journal of X-Ray Science and Technology - Volume 23, issue 5
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Journal of X-Ray Science and Technology is an international journal designed for the diverse community (biomedical, industrial and academic) of users and developers of novel x-ray imaging techniques. The purpose of the journal is to provide clear and full coverage of new developments and applications in the field.
Areas such as x-ray microlithography, x-ray astronomy and medical x-ray imaging as well as new technologies arising from fields traditionally considered unrelated to x rays (semiconductor processing, accelerator technology, ionizing and non-ionizing medical diagnostic and therapeutic modalities, etc.) present opportunities for research that can meet new challenges as they arise.
Abstract: Baggage inspection is the principal safeguard against the transportation of prohibited and potentially dangerous materials at airport security checkpoints. Although traditionally performed by 2D X-ray based scanning, increasingly stringent security regulations have led to a growing demand for more advanced imaging technologies. The role of X-ray Computed Tomography is thus rapidly expanding beyond the traditional materials-based detection of explosives. The development of computer vision and image processing techniques for the automated understanding of 3D baggage-CT imagery is however, complicated by poor image resolutions, image clutter and high levels of noise and artefacts. We discuss the recent and most pertinent advancements…and identify topics for future research within the challenging domain of automated image understanding for baggage security screening CT.
Abstract: PURPOSE: The aim of this study is to investigate the association between the cardiothoracic ratio (CTR), transverse cardiac diameter (TCD), and left ventricular (LV) size and systolic function in patients with or without preserved LV ejection fraction (LVEF). METHODS: A total of 181 subjects suspected with coronary artery disease underwent chest radiography (CR) and dual source computed tomography coronary angiography (DSCT-CA). TCD and CTR were derived from CR. The LV size and systolic function parameters, such as LV end-diastolic volume (LVEDV), LV end-systolic volume (LVESV) and LVEF were measured from DSCT-CA. The association between TCD, CTR…and LV size and systolic function parameters were analyzed according to LVEF value (< 55%, depressed LVEF group; versus ≥ 55%, preserved LVEF group). RESULTS: Both TCD and CTR were higher in the depressed LVEF group compared with the preserved LVEF group. Significant correlations were found between TCD, CTR and LVEDV, LVESV, LVEF in depressed LVEF group. However, there was no significant association detected between CTR and LV size and systolic function parameters in preserved LVEF group. Both the LVEDV and LVESV showed a positive correlation with TCD in preserved LVEF group. CONCLUTION: Although CTR was not a reliable indicator of LV size and systolic function in patients with preserved LVEF, it was correlated with LV size and LVEF in depressed LVEF patients. Furthermore, TCD showed stronger correlations with LV size and systolic function even in patients with preserved LVEF.
Keywords: Transverse cardiac diameter, cardiothoracic ratio, left ventricular systolic function, left ventricular size
Abstract: Reducing X-ray tube current is one of the widely used methods for decreasing the radiation dose. Unfortunately, the signal-to-noise ratio (SNR) of the projection data degrades simultaneously. To improve the quality of reconstructed images, a dictionary learning based penalized weighted least-squares (PWLS) approach is proposed for sinogram denoising. The weighted least-squares considers the statistical characteristic of noise and the penalty models the sparsity of sinogram based on dictionary learning. Then reconstruct CT image using filtered back projection (FBP) algorithm from the denoised sinogram. The proposed method is particularly suitable for the projection data with low SNR. Experimental results show that…the proposed method can get high-quality CT images when the signal to noise ratio of projection data declines sharply.
Abstract: OBJECTIVE: This study aimed to propose an intensity-vesselness Gaussian mixture model (IVGMM) tracking for 2D + t segmentation of coronary arteries for X-ray angiography (XA) image sequences. METHODS: We compose a two dimensional (2D) feature vector of intensity and vesselness to characterize the Gaussian mixture models. In our IVGMM tracking, vessel segmentation is performed for each image frame based on these vessel and background IVGMMs and then the segmentation results of the current image frame is used to update these IVGMMs. The 2D + t segmentation of coronary arteries over the 2D XA image sequence…is solved by means of iterating two processes, i.e., segmentation of coronary arteries and update of the IVGMMs. RESULTS: The performance of the proposed IVGMM tracking was evaluated using clinical 2D XA datasets. We evaluated the segmentation accuracy of the IVGMM tracking by comparing with two previous 2D vessel segmentation methods and seven background subtraction (BGS) methods. Of the ten segmentation methods, IVGMM tracking shows the highest similarity to the manual segmentation in terms of precision, recall, Jaccard index (JI), F1 score, and peak signal-to-noise ratio (PSNR). CONCLUSIONS: It is concluded that the IVGMM tracking could obtain reasonable segmentation accuracy outperforming conventional vessel enhancement methods and object tracking methods.
Abstract: Knowledge of scatter generated by bowtie filter (i.e. x-ray beam compensator) is crucial for providing artifact free images on the CT scanners. Our approach is to use a hybrid deterministic-stochastic simulation to estimate the scatter level generated by a bowtie filter made of a material with low atomic number. First, major components of CT systems, such as source, flat filter, bowtie filter, body phantom, are built into a 3D model. The scattered photon fluence and the primary transmitted photon fluence are simulated by MCNP - a Monte Carlo simulation toolkit. The rejection of scattered photon by the post patient collimator…(anti-scatter grid) is simulated with an analytical formula. The biased sinogram is created by superimposing scatter signal generated by the simulation onto the primary x-ray beam signal. Finally, images with artifacts are reconstructed with the biased signal. The effect of anti-scatter grid height on scatter rejection are also discussed and demonstrated.
Keywords: Bowtie filter, scatter, Monte Carlo simulation, deterministic method
Abstract: OBJECTIVE: Complex calculi in horseshoe kidney (HK) present a significant management challenge. Here, we report the clinical efficacy of extracorporeal shock wave lithotripsy (ESWL), minimally invasive percutaneous nephrolithotomy (MPCNL) and flexible ureteroscopy (FURS), combined with holmium laser lithotripsy, in the treatment of calculi in HK. METHODS AND RESULTS: From January 2005 to May 2014, 62 HK patients with renal calculi were reviewed in terms of medical history, treatment modality and therapeutic outcome in a single tertiary care hospital. Among the patients, 11 with a solitary stone ≤ 1.5 cm in diameter received ESWL, leading to…overall stone-free rate of 72.7%; 18 with stone diameter ≤ 2-3 cm received retrograde flexible ureteroscopy, with a recorded mean digitized surface area (DSA) of 339.6 ± 103.9 mm2 , mean operation time of 93.1 ± 11.5 minutes and overall stone-free rate of 88.9%; and 33 with staghorn or complex calculi (d ≥ 2 cm) had MPCNL or MPCNL-FURS, with a recorded mean DSA of 691.0 ± 329.9 vs. 802.9 ± 333.3 mm2 , mean operation time of 106.4 ± 16.6 vs. 124.4 ± 15.1 min and overall stone-free rate of 89.5% vs. 92.9%. For complex calculi (d ≥ 2 cm), MPCNL combined with antegrade FURS was superior in terms of reducing number of tracts, controlling mean hemoglobin drop, but required longer operation time, comparing with MPCNL alone. CONCLUSIONS: As minimally invasive treatments, a combination of MPCNL and antegrade FURS provides a safe and effective modality in the management of staghorn or complex calculi (d ≥ 2 cm) in HK with significantly reduced blood loss comparing to MPCNL alone, and retrograde FURS alone is favorable for stones with a diameter ≤ 2-3 cm. ESWL is effective for viable small solitary stones (d ≤ 1.5 cm). Treatment modality should be tailored based on individual condition.
Abstract: The octahedron (BO6 ) plays a crucial role in ground state for the layered perovskites oxides. Here, we report a structure study of the octahedra in Sr2 Ru1-x Mnx O4 based on Extended X-ray Absorption Fine Structure (EXAFS) method. EXAFS results reveal a clearly structural distortion around the doped Mn atoms, and Jahn-Teller effect in MnO6 octahedra could be expected in the octahedra. This structural distortion may related to the chemical valance change when doping.
Abstract: OBJECTIVE: Despite various X-ray approaches have been widely used to monitor root resorption after orthodontic treatment, a non-invasive and accurate method is highly desirable for long-term follow up. The aim of this study was to build a non-invasive method to quantify longitudinal orthodontic root resorption with time-lapsed images of micro-computed tomography (micro-CT) in a rodent model. MATERIALS AND METHODS: Twenty male Sprague Dawley (SD) rats (aged 6-8 weeks, weighing 180-220 g) were used in this study. A 25 g orthodontic force generated by nickel-titanium coil spring was applied to the right maxillary first molar for…each rat, while contralateral first molar was severed as a control. Micro-CT scan was performed at day 0 (before orthodontic load) and days 3, 7, 14, and 28 after orthodontic load. Resorption of mesial root of maxillary first molars at bilateral sides was calculated from micro-CT images with registration algorithm via reconstruction, superimposition and partition operations. RESULTS: Obvious resorption of mesial root of maxillary first molar can be detected at day 14 and day 28 at orthodontic side. Most of the resorption occurred in the apical region at distal side and cervical region at mesiolingual side. Desirable development of molar root of rats was identified from day 0 to day 28 at control side. The development of root concentrated on apical region. CONCLUSIONS: This non-invasive 3D quantification method with registration algorithm can be used in longitudinal study of root resorption. Obvious root resorption in rat molar can be observed three-dimensionally at day 14 and day 28 after orthodontic load. This indicates that registration algorithm combined with time-lapsed images provides clinic potential application in detection and quantification of root contour.
Abstract: It is well known that CT projections are redundant. Over the past decades, significant efforts have been devoted to characterize the data redundancy in different aspects. Very recently, Clackdoyle and Desbat reported a new integral-type data consistency condition (DCC) for truncated 2D parallel-beam projections, which can be applied to a region inside a field of view (FOV) but outside of the convex hull of the compact support of an object. Inspired by their work, here we derive a more general condition for 2D fan-beam geometry with a general scanning trajectory. This extended DCC is verified with simulated projections of the…Shepp-Logan phantom and a clinically collected sinogram. Then, we demonstrate an application of the proposed DCC.
Keywords: Data consistency condition, fan-beam geometry, truncated projections, general scanning trajectory, interior problem, motion artifact reduction
Abstract: BACKGROUND: In OCT system, the chromatic dispersion of sample decreases the resolution and increases the depth misplacement. The developed numerical dispersion compensation techniques usually do not consider the higher order dispersion and time-consuming. OBJECTIVE: We proposed a numerical compensation technique for correcting depth error and resolution deterioration in Fourier domain optical coherence tomography (FD-OCT). METHODS: Firstly, the rough depth of each scatter in multilayer sample is estimated through magnification curve. Then the depth of a scatter is iterated to minimum the residual of this scatter in the time domain. At last, the spectrum…of the scatter is reconstructed and dispersion can be compensated with the tracked depth. RESULTS: The results show that the depth error is corrected to less than resolution level and the resolution is corrected to nearly ideal. CONCLUSIONS: The technique proposed can provide precise sample tomography, thus enhancing the understanding of sample character.