Journal of X-Ray Science and Technology - Volume 26, issue 4
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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: Statistical noise may degrade the x-ray image quality of digital radiography (DR) system. This corruption can be alleviated by extending exposure time of detectors and increasing the intensity of radiation. However, in some instances, such as the security check and medical imaging examination, the system demands rapid and low-dose detection. In this study, we propose and test a generative adversarial network (GAN) based x-ray image denoising method. Images used in this study were acquired from a digital radiography (DR) imaging system. Promising results have been obtained in our experiments with x-ray images for the security check application. The Experiment results…demonstrated that the proposed new image denoising method was able to effectively remove the statistical noise from x-ray images, while kept sharp edge and clear structure. Thus, comparing with the traditional convolutional neural network (CNN) based method, the proposed new method generates more plausible-looking images, which contains more details.
Keywords: Digital radiography, image denoising, generative adversarial network
Abstract: Hounsfield Units (HU) are used clinically in differentiating tissue types in a reconstructed CT image, and therefore the HU accuracy of a system is important, especially when using multiple sources, novel detector and non-traditional trajectories. Dedicated clinical breast CT (BCT) systems therefore should be similarly evaluated. In this study, uniform cylindrical phantoms filled with various uniform density fluids were used to characterize differences in HU values between simple circular and complex 3D (saddle) orbits. Based on ACR recommendations, the HU accuracy, center-to-edge variability within a slice, and overall variability within the reconstructed volume were characterized for simple and complex acquisitions…possible on a single versatile BCT system. Results illustrate the statistically significantly better performance of the saddle orbit, especially close to the chest and nipple regions of what would clinically be a pendant breast volume. The incomplete cone beam acquisition of a simple circular orbit causes shading artifacts near the nipple, due to insufficient sampling, rendering a major portion of the scanned phantom unusable, whereas the saddle orbit performs exceptionally well and provides a tighter distribution of HU values throughout the reconstructed volumes. This study further establishes the advantages of using 3D acquisition trajectories for breast CT as well as other applications by demonstrating the robustness of HU values throughout large reconstructed volumes.
Keywords: Breast CT, complex trajectories, HU, 3D sampling
Abstract: BACKGROUND: Breast cancer, the most common malignancy among women, has a high mortality rate in clinical practice. Early detection, diagnosis and treatment can reduce the mortalities of breast cancer greatly. The method of mammogram retrieval can help doctors to find the early breast lesions effectively and determine a reasonable feature set for image similarity measure. This will improve the accuracy effectively for mammogram retrieval. METHODS: This paper proposes a similarity measure method combining location feature for mammogram retrieval. Firstly, the images are pre-processed, the regions of interest are detected and the lesions are segmented in order to get…the center point and radius of the lesions. Then, the method, namely Coherent Point Drift, is used for image registration with the pre-defined standard image. The center point and radius of the lesions after registration are obtained and the standard location feature of the image is constructed. This standard location feature can help figure out the location similarity between the image pair from the query image to each dataset image in the database. Next, the content feature of the image is extracted, including the Histogram of Oriented Gradients, the Edge Direction Histogram, the Local Binary Pattern and the Gray Level Histogram, and the image pair content similarity can be calculated using the Earth Mover’s Distance. Finally, the location similarity and content similarity are fused to form the image fusion similarity, and the specified number of the most similar images can be returned according to it. RESULTS: In the experiment, 440 mammograms, which are from Chinese women in Northeast China, are used as the database. When fusing 40% lesion location feature similarity and 60% content feature similarity, the results have obvious advantages. At this time, precision is 0.83, recall is 0.76, comprehensive indicator is 0.79, satisfaction is 96.0%, mean is 4.2 and variance is 17.7. CONCLUSIONS: The results show that the precision and recall of this method have obvious advantage, compared with the content-based image retrieval.
Abstract: X-ray Computed Tomography (XCT) has become an important tool for industrial measurement and quality control through its ability to measure internal structures and volumetric defects. Segmentation of constituent materials in the volume acquired through XCT is one of the most critical factors that influence its robustness and repeatability. Highly attenuating materials such as steel can introduce artefacts in CT images that adversely affect the segmentation process, and results in large errors during quantification. This paper presents a Markov Random Field (MRF) segmentation method as a suitable approach for industrial samples with metal artefacts. The advantages of employing the MRF segmentation…method are shown in comparison with Otsu thresholding on CT data from two industrial objects.
Keywords: Computed tomography, Markov Random Fields, segmentation, metal artefacts
Abstract: PURPOSE: Metal artifacts severely degrade CT image quality in clinical diagnosis, which are difficult to removed, especially for the beam hardening artifacts. The metal artifact reduction (MAR) based on prior images are the most frequently-used methods. However, there exists a lot misclassification in most prior images caused by absence of prior information such as the spectrum distribution of X-ray beam source, especially many or big metal included. The purpose of this work is to find a more accurate prior image to improve image quality. METHODS: The proposed method comprise of following four steps. First, the metal image is…segmented by thresholding an initial image, where the metal traces are identified in the initial projection data using the forward projection of the metal image. Second, the accurate absorbent model of certain metal image is calculated according to the spectrum distribution of certain X-ray beam source and energy-dependent attenuation coefficients of metal. Then, a new metal image is reconstructed by the general analytical reconstruction algorithm such as filtered back projection (FPB). The prior image is obtained by segmenting the difference image between the initial image and the new metal image into air, tissue and bone. Finally, the initial projection data are normalized by dividing the projection data of prior image pixel to pixel, the corrected image is obtained by interpolation, denormalization and reconstruction. RESULTS: Some clinical images with dental fillings and knee prostheses are used to evaluate the proposed algorithm and normalized metal artifact reduction (NMAR) and linear interpolation (LI) method. The results demonstrate the artifacts can be reduced efficiently by the proposed method. CONCLUSIONS: The proposed method could obtain an exact prior image using the prior information about X-ray beam source and energy-dependent attenuation coefficients of metal. As a result, the better performance of reducing beam hardening artifacts can be improved, even though there were many or big implants. Moreover, the process of the proposed method is rather simple and little extra calculation burden is necessary. It has superiorities over other algorithms when include big or many implants.
Keywords: X-ray CT, metal artifact, beam hardening, LI, NMAR
Abstract: Excessive radiation exposure in computed tomography (CT) scans increases the chance of developing cancer and has become a major clinical concern. Recently, statistical iterative reconstruction (SIR) with l 0 -norm dictionary learning regularization has been developed to reconstruct CT images from the low dose and few-view dataset in order to reduce radiation dose. Nonetheless, the sparse regularization term adopted in this approach is l 0 -norm, which cannot guarantee the global convergence of the proposed algorithm. To address this problem, in this study we introduced the l 1 -norm dictionary learning penalty into SIR framework for low dose CT image…reconstruction, and developed an alternating minimization algorithm to minimize the associated objective function, which transforms CT image reconstruction problem into a sparse coding subproblem and an image updating subproblem. During the image updating process, an efficient model function approach based on balancing principle is applied to choose the regularization parameters. The proposed alternating minimization algorithm was evaluated first using real projection data of a sheep lung CT perfusion and then using numerical simulation based on sheep lung CT image and chest image. Both visual assessment and quantitative comparison using terms of root mean square error (RMSE) and structural similarity (SSIM) index demonstrated that the new image reconstruction algorithm yielded similar performance with l 0 -norm dictionary learning penalty and outperformed the conventional filtered backprojection (FBP) and total variation (TV) minimization algorithms.
Abstract: OBJECTIVE: To investigate the clinical significance of antiplatelet aggregation therapy for patients diagnosed with acute cerebral infarction (ACI) complicated with the cerebral microbleeds (CMBs). METHODS: Thirty patients with ACI and 36 patients with intracerebral hemorrhage (ICH) were included in this research. Two groups, studied by susceptibility-weighted imaging (SWI), were compared in terms of the number, location, and severity of CMBs. Then, 30 cases of ACI patients were divided into CMBs sub-group and non-CMBs sub-group. Univariate analysis between these two sub-groups was performed to determine the risk factors regarding the incidence of CMBs. For ACI patients, the number of…CMBs before and after applying anti-platelet treatment were compared to examine the impacts of anti-platelet treatment on hemorrhagic transformation. RESULTS: CMBs were found to be more prevalent and severe in ICH patients than in ACI patients. CMBs in patients with ICH were more severe than in patients with ischemic stroke (IS), which indicates that CMBs closely relate to ICH. Hypertension and leukoaraiosis were found to have significant effects on the incidence of CMBs. After anti-platelet treatment, patients with CMBs (≥5) increased the number of CMB, whereas there was no obvious effect on patients with the CMBs less than 5 or no CMBs. CONCLUSIONS: The number of CMBs increased significantly among ACI patients with 5 or more CMBs before the anti-platelet treatment. CMBs are more frequently found in patients with hemorrhagic stroke than in patients with ischemic stroke, and more severe than the latter, which suggests that the clinical impact of higher association between the increase of the number of the CMBs and the hemorrhagic stroke.
Abstract: OBJECTIVE: To evaluate the relationship of microhemorrhage on susceptibility-weighted imaging (SWI) with the severity of clinical symptoms and the prognosis of viral encephalitis. MATERIALS AND METHODS: Thirty patients with clinically diagnosed viral encephalitis were divided into three groups according to the Glasgow Coma Scale (GCS) and the condition of recovery namely, Group I (n = 12): Glasgow Coma Scale (GCS)≥13 and recovered with no sequelae; Group II (n = 11): GCS 9–12 and recovered with some sequelae; Group III (n = 7): GCS 3–8 and recovered with more severe sequelae. The microhemorrhage detectability on SWI…and conventional MR imaging in these three groups was compared and their correlations with different seriousness of clinical symptoms and prognosis were analyzed. RESULTS: There was a significant difference in microhemorrhage volume among different MR sequences (p < 0.05). SWI was more sensitive to detect microhemorrhage than conventional MR imaging techniques. Microhemorrhages on SWI were significantly different among the three groups (p < 0.01). The volume of microhemorrhage on SWI was well correlated with the degree of clinical symptoms and the prognosis of viral encephalitis. CONCLUSION: SWI can be used to detect microhemorrhage in patients with viral encephalitis. Assessment of microhemorrhage with SWI can provide useful information for the prognosis evaluation of viral encephalitis.
Abstract: BACKGROUND: Eurycoma longifolia (EL) is a well-known aphrodisiac herb for men. Recently, the crude extract of EL was reported to possess anti-osteoporotic activities. OBJECTIVE: This study aims to determine the bone protective effects of the standardized quassinoid-rich EL extract in testosterone-deficient rat model. METHODS: Ninety-six intact male Sprague-Dawley rats were randomized into baseline, sham, orchidectomized, and chemically castrated groups. Chemical castration was performed via subcutaneous injection of degarelix at 2 mg/kg. The orchidectomized and degarelix-induced rats were administered with vehicle, intramuscularly injected with testosterone once a week, or orally supplemented with EL extract at doses of…25 mg/kg, 50 mg/kg or 100 mg/kg daily for 10 weeks. Bone mass, microarchitecture and strength were analyzed by dual-energy x-ray absorptiometry (DEXA), micro-CT and three-point bending test. RESULTS: Whole body bone mineral density and femoral bone mineral content significantly increased in testosterone groups (p < 0.05). Micro-CT analysis revealed that trabecular bone volume, number, separation and connectivity density were significantly improved by testosterone administration. However, the structural model index was only improved in degarelix group supplemented with 100 mg/kg EL extract (P < 0.05). The improvement of cortical thickness by EL extract was similar to that of testosterone groups (p < 0.05). Biomechanically, EL extract supplementation was able to improve stiffness, strain and modulus of elasticity in degarelix-induced groups, while stress parameter was significantly improved in orchidectomized groups (p < 0.05). CONCLUSION: Quassinoid-rich EL extract enables to protect against bone loss due to testosterone deficiency. The protective effect on cortical thickness and biomechanical parameters is comparable to testosterone group.
Keywords: Bone mineral, micro-CT, bone strength, bone loss, Tongkat Ali
Abstract: BACKGROUND: Differences often exist in the dose calculation accuracy caused by using different dose calculation algorithms in non-uniform tissues. OBJECTIVE: To evaluate the accuracy of dose calculation with inhomogeneity correction in intensity-modulated radiation therapy (IMRT) by comparing dose calculated in Monaco with measurements in lung-chest phantom for esophagus cancer treatments. METHODS: Finite size pencil beam (FSPB) and X-ray voxel Monte Carlo (XVMC) were used respectively for IMRT dose recalculations. Ten IMRT plans were recalculated and measured in the chest-lung phantom. The dose measurements using the Gafchromic ® (EBT3) dosimetry films were validated with open fields…in the interfaces of materials with various physical densities. The accuracy of dose calculations was then evaluated by both point dose comparison and Gamma analysis against the film measurements. RESULTS: For regular open fields, the discrepancies of the point doses were less than 3.0% and 2.0% between measurement and calculations by FSPB and XVMC, respectively. For 6 MV IMRT plans, the average passing rates based on 3% /3 mm Gamma criteria were 82.8±1.0% and 96.4±0.7% for FSPB and XVMC, respectively. CONCLUSIONS: The XVMC algorithms more accurate in IMRT dose calculations with inhomogeneity correction for esophagus cancer.
Keywords: Dose calculation, intensity-modulated radiation therapy (IMRT), inhomogeneity correction, X-ray voxel Monte Carlo (XVMC)