Microstructure Evolution of Sandstone Cemented by Microbe Cement Using X-ray Computed Tomography

The bio-sandstone, which was cemented by microbe cement, was firstly prepared, and then the microstructure evolution process was studied by X-ray computed tomography （X-CT） technique. The experimental results indicate that the microstructure of bio-sandstone becomes dense with the development of age. The evolution of inner structure at different positions is different due to the different contents of microbial induced precipitation calcite. Besides, the increase rate of microbial induced precipitation calcite gradually decreases because of the reduction of microbe absorption content with the decreasing pore size in bio-sandstone.

Use of high-resolution X-ray computed tomography and 3D image analysis to quantify mineral dissemination and pore space in oxide copper ore particles

Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance. To quantify the mineral dissemination and pore space distribution of an ore particle, a cylindrical copper oxide ore sample (I center dot 4.6 mm x 5.6 mm) was scanned using high-resolution X-ray computed tomography (HRXCT), a nondestructive imaging technology, at a spatial resolution of 4.85 mu m. Combined with three-dimensional (3D) image analysis techniques, the main mineral phases and pore space were segmented and the volume fraction of each phase was calculated. In addition, the mass fraction of each mineral phase was estimated and the result was validated with that obtained using traditional techniques. Furthermore, the pore phase features, including the pore size distribution, pore surface area, pore fractal dimension, pore centerline, and the pore connectivity, were investigated quantitatively. The pore space analysis results indicate that the pore size distribution closely fits a log-normal distribution and that the pore space morphology is complicated, with a large surface area and low connectivity. This study demonstrates that the combination of HRXCT and 3D image analysis is an effective tool for acquiring 3D mineralogical and pore structural data.

In situ compression and X-ray computed tomography of flow battery electrodes

Redox flow batteries offer a potential solution to an increase in renewable energy generation on the grid by offering long-term, large-scale storage and regulation of power. However, they are currently un- derutilised due to cost and performance issues, many of which are linked to the microstructure of the porous carbon electrodes used. Here, for the first time, we offer a detailed study of the in situ effects of compression on a commercially available carbon felt electrode. Visualisation of electrode structure us- ing X-ray computed tomography shows the non-linear way that these materials compress and various metrics are used to elucidate the changes in porosity, pore size distribution and tortuosity factor under compressions from 0%-90%.

X-ray Computed Tomography Characterization of 3D Tufted Twill Textile Composite for Aerostructures

Damage assessments in three dimensional (3D) textile composites subjected to mechanical loading can be performed by non-destructive and destructive techniques.This paper applies the two techniques to investigate the fracture behavior of 3D tufted textile composites.X-ray computed tomography as a non-destructive evaluation method is appropriate to detect damage locations and identify their progression in 3D textile composites.Destructive methods such as sectioning toward observing damage provide valuable information about damage patterns.The results of this research could be utilized to evaluate the initial cause of rupture in 3D tufted composites used in aerospace structures and analyze fracture modes and damage progression.

X-Ray Computed Tomography for Root Quantification

Soil cores from a field growing barley and barley mutants without root hairs under conventional and minimum tillage were sampled. They were X-ray scanned to produce a 3D image and then the roots were washed out and weight and length were determined by conventional means. Root volume and surface area were then calculated from the 3D images using state of the art software and methodology, and the measured and calculated measures were correlated. The only strong and significant correlation was between measured weight and calculated volume for mutants without root hairs. It is concluded that the software cannot segment out very small roots, but segmentation accuracy also depends on root structure in some unknown way. Any study using X-ray computed tomography to quantify roots as they grow in situ should start with a calibration for the conditions in question.

Usefulness of Chest Computed Tomography for Diagnosis of Idiopathic Pneumomediastinum with Negative Findings on Plain X-Ray

Idiopathic pneumomediastinum is rare in children. Few cases of patients with pneumomediastinum show negative findings on X-ray examination. Chest computed tomography (CT) was very useful for the diagnosis and evaluation of the extent of pneumomediastinum. We report here a case of idiopathic pneumomediastinum in a 15-year-old boy who exhibited no significant chest X-ray finding. The patient was referred to our institute for the further evaluation of pre-cordial pain and breathing difficulty. Precordial pain suddenly developed, when he was carrying a portable shrine on his shoulder (day of onset). He was admitted to another institute 3 days after onset because of worsening precordial pain. On admission, he presented with 98% saturation of hemoglobin in the peripheral blood under room air. Plain chest X-ray also revealed no abnormal findings. A half-dissolved gastrographin swallow showed no leakage of gastrographin from the pharynx and esophagus to the mediastinum, and no diverticulum within the esophagus. Plain chest CT revealed extensive emphysema around the trachea from the neck to the portion inferior to the carina of trachea. The patient was diagnosed with idiopathic pneumomediastinum because the cause was unclear. We decided to admit him to our institute under fasting conditions and rest. His symptoms improved 3 days after onset. The lesion had disap-peared 8 days after onset on chest CT. When young people experience precordial pain which increases on inspiration, we must consider pneumomediastinum in a differential diagnosis, and it is important to perform chest CT.

Quantification of 3D macropore networks in forest soils in Touzhai valley(Yunnan,China)using X-ray computed tomography and image analysis

The three dimensional(3D) geometry of soil macropores largely controls preferential flow, which is a significant infiltrating mechanism for rainfall in forest soils and affects slope stability. However, detailed studies on the 3D geometry of macropore networks in forest soils are rare. The intense rainfall-triggered potentially unstable slopes were threatening the villages at the downstream of Touzhai valley(Yunnan, China). We visualized and quantified the 3D macropore networks in undisturbed soil columns(Histosols) taken from a forest hillslope in Touzhai valley, and compared them with those in agricultural soils(corn and soybean in USA; barley, fodder beet and red fescue in Denmark) and grassland soils in USA. We took two large undisturbed soil columns(250 mm×250 mm×500 mm), and scanned the soil columns at in-situ soil water content conditions using X-ray computed tomography at a voxel resolution of 0.945 × 0.945 × 1.500 mm^3. After reconstruction and visualization, we quantified the characteristics of macropore networks. In the studiedforest soils, the main types of macropores were root channels, inter-aggregate voids, macropores without knowing origin, root-soil interface and stone-soil interface. While macropore networks tend to be more complex, larger, deeper and longer. The forest soils have high macroporosity, total macropore wall area density, node density, and large macropore volume, hydraulic radius, mean macropore length, angle, and low tortuosity. The findings suggest that macropore networks in the forest soils have high interconnectivity, vertical continuity, linearity and less vertically oriented.

Computed tomography versus transthoracic echocardiography in the detection of complex congenial heart diseases in china:a meta-analysis

Objective:To perform a meta-analysis to evaluate the diagnostic performance of computed tomography(CT) and transthoracic echocardiography(TTE) in complex congenital heart diseases(CHD) in China.Methods:MEDLINE,Cochrane library and China National Knowledge Infrastructure(CNKI) database from January 1966 to October 2010,were searched for initial studies in China.All the studies,published in English or Chinese,used TTE,CT,or both as diagnostic tests for CHD and reported the rate of true-positive,true-negative,false-positive and false-negative diagnoses of CHD from TTE and CT findings with the surgical results as the 'gold-standard'(15 studies,XX patients) were collected.The statistic software package,'Meta-Disc 1.4',was used to conduct data analysis.A covariate analysis was used to evaluate the influence of patient or study-related factors on sensitivity.Results:Pooled sensitivity for diagnosis of CHD were 95% [95% confidence interval(CI):94%~96%] for CT studies and 87%(95% CI:85%~88%) for TTE studies.The difference between the pooled sensitivity of CT and that of TTE was statistically significant(P<0.001).TTE had higher sensitivity [0.96(95% CI:0.94~0.97)] for cardiac malformation but lower sensitivity [0.78(95% CI:0.76~0.81)] for extracardiac malformation than CT.Conclusion:CT can provide added diagnostic information compared with TTE in patients with CHD in China,especially for patients suspected of extracardiac malformation.

Infective severe acute pancreatitis:A comparison of ^(99m)Tc-ciprofloxacin scintigraphy and computed tomography

AIM:To evaluate 99mTc-ciprofloxacin scintigraphy compared with computed tomography(CT)for detecting secondary infections associated with severe acute pancreatitis(SAP)in swine.METHODS:Six healthy swine were assigned to a normal control group(group A,n = 6).SAP was induced in group B(n = 9)and C(n = 18),followed by inoculation of the resulting pancreatic necroses with inactive Escherichia coli(E.coli)(group B)and active E.coli(group C),respectively.At 7 d after inoculation,a CT scan and a series of analyses using infecton imaging(at 0.5,1,2,3,4 and 6 h after the administration of 370 MBq of intravenous infecton)were performed.The scintigrams were visually evaluated and semi-quantitatively analyzed using region of interest assignments.The differences in infecton uptake and changes in the lesion-background radioactive count ratios(L/B)in the 3 groups were recorded and compared.After imaging detection,histopathology and bacterial examinations were performed,and infected SAP was regarded as positive.The imaging findings were compared with histopathological and bacteriological results.RESULTS:In group A,6 animals survived without infection in the pancreas.In group B,7/9 swine survived and one suffered from infection.In group C,15/18 animals survived with infection.Hence,the number of normal,non-infected and infected SAP swine was 6,6 and 16,respectively.The sensitivity,specificity,accuracy,positive predictive value and negative predictive value of the infecton method were 93.8%(15/16),91.7%(11/12),92.9%(26/28),93.8%(15/16)and 91.7%(11/12),whereas these values for CT were 12.5%(2/16),100.0%(12/12),50.0%(14/28),100.0%(2/2)and 46.2%(12/26),respectively.The changes in L/B for the infected SAP were significantly different from those of the non-infected and normal swine(P < 0.001).The mean L/B of the infectious foci at 0.5,1,2,3,4 and 6 h was 1.17 ± 0.10,1.71 ± 0.30,2.46 ± 0.45,3.36 ± 0.33,2.04 ± 0.37 and 1.1988 ± 0.09,respectively.At 3 h,the radioactive counts(2350.25 ± 602.35 k)and the mean L/B of the infectious foci were significantly higher than that at 0.5 h(P = 0.000),1 h(P = 0.000),2 h(P = 0.04),4 h(P = 0.000)and 6 h(P = 0.000).CONCLUSION:99m Tc-ciprofloxacin scintigraphy may be an effective procedure for detecting SAP secondary infections with higher sensitivity and accuracy than CT.

Investigation of noise properties in grating-based x-ray phase tomography with reverse projection method

The relationship between noise variance and spatial resolution in grating-based x-ray phase computed tomography（PCT） imaging is investigated with reverse projection extraction method, and the noise variances of the reconstructed absorption coefficient and refractive index decrement are compared. For the differential phase contrast method, the noise variance in the differential projection images follows the same inverse-square law with spatial resolution as in conventional absorption-based x-ray imaging projections. However, both theoretical analysis and simulations demonstrate that in PCT the noise variance of the reconstructed refractive index decrement scales with spatial resolution follows an inverse linear relationship at fixed slice thickness, while the noise variance of the reconstructed absorption coefficient conforms with the inverse cubic law. The results indicate that, for the same noise variance level, PCT imaging may enable higher spatial resolution than conventional absorption computed tomography（ACT）, while ACT benefits more from degraded spatial resolution. This could be a useful guidance in imaging the inner structure of the sample in higher spatial resolution.

Effective Atomic Number Measurement with Energy-Resolved Computed Tomography Using Two-Dimensional “transXend” Detector

Introduction: We have previously developed an effective atomic number (Zeff) measurement method using linear attenuation coefficients (LACs) obtained by energy-resolved computed tomography (CT) with one-dimensional (1D) detector. The energy-resolved CT was performed with a “transXend” detector, which measured X-rays as electric current and then gave X-ray energy distribution with unfolding analysis using pre-estimated response function (RF). The purpose of this study is to measure Zeff by the energy-resolved CT using a flat panel detector (FPD). Methods: To demonstrate a 2D transXend detector, we developed the stripe absorbers for the FPD. Eleven human tissue-equivalent material rods which were grouped into four material categories were measured by X-rays with 120 kVp tube voltage, 2.3 mA tube current, and 1.0 s exposure time. Zeff is measured by the ratio of LACs with two different pseudo-monochromatic X-ray energies. RFs of each rod material were estimated by numerical calculation. First, we employed the RF estimated for the same rod material (self-RF scenario). Second, we employed the RF estimated for the different rod materials in the same material category (cross-RF scenario). The purpose of the cross-RF scenario was to find representative rod materials in each material category. Results: Upon the self-RF scenario, measured Zeffs were systematically underestimated. Median relative error to theoretical Zeff was -6.92% (range: -7.89% - -4.60%). After normalizing measured Zeffs to the theoretical one for Breast, median relative error improved to -0.75% (range: -1.79% - +1.73%). Upon the cross-RF scenario, the representative rod materials were found in two material categories. Conclusion: Zeff measurements were performed by energy-resolved CT using 2D transXend detector with numerically-estimated RF data. Normalized Zeffs for all rod materials in the self-RF scenario were in good agreement with the theoretical ones.

Reduction of the Beam Hardening Artifacts in the X-Ray Computer Tomography: Energy Discrimination with a Photon-Counting Detector

The material identification is a pressing requirement for the sensitive security applications. Dual-energy X-ray computer tomography (DXCT) has been investigated for material identification in the medical and security fields. It requires two tomographic images at sufficiently different energies. To discriminate dangerous materials of light elements such as plastic bombs in luggage, it is needed to measure accurately with several tens of kilo electron volts where such materials exhibit significant spectral differences. However, CT images in that energy region often include artifacts from beam hardening. To reduce these artifacts, a novel reconstruction method has been investigated. It is an extension of the Al-gebraic Reconstruction Technique and Total Variation (ART-TV) method that reduces the artifacts in a lower-energy CT image by referencing it to an image obtained at higher energy. The CT image of a titanium sample was recon-structed using this method in order to demonstrate the artifact reduction capability.

Head dual energy-computed tomography angiography versus neuro-digital subtraction angiography

Dual-energy X-ray absorptiometry provides two modes of head computed tomography （CT） angiography scanning： neuro-digital subtraction angiography and dual-energy CT angiography （DE-CTA）. Previous studies have compared image quality, radiation exposure, and bone removal between neuro-digital subtraction angiography and DE-CTA. However, the number of cases was relatively small. The present study examined 300 suspected cases of cerebrovascular disease and observed the methods and duration of post-processing, examination time, and data volume. Results demonstrated similar image quality between the two methods, but lower radiation doses and shorter examination time in DE-CTA. DE-CTA allowed for faster and more stable scanning performance and post-processing methods, facilitating accurate and direct diagnosis of cerebrovascular disease.

Radiomic features from computed tomography to differentiate invasive pulmonary adenocarcinomas from non-invasive pulmonary adenocarcinomas appearing as part-solid groundglass nodules

Objective:We aim to investigate radiomic imaging features extracted in computed tomography(CT)images to differentiate invasive pulmonary adenocarcinomas(IPAs)from non-IPAs appearing as part-solid ground-glass nodules(GGNs),and to incorporate significant radiomic features with other clinically-assessed features to develop a diagnostic nomogram model for IPAs.Methods:This retrospective study was performed,with Institutional Review Board approval,on 88 patients with a total of 100 part-solid nodules(56 IPAs and 44 non-IPAs)that were surgically confirmed between February 2014and November 2016 in the First Affiliated Hospital of China Medical University.Quantitative radiomic features were computed automatically on 3D nodule volume segmented from arterial-phase contrast-enhanced CT images.A set of regular risk factors and visually-assessed qualitative CT imaging features were compared with the radiomic features using logistic regression analysis.Three diagnostic models,i.e.,a basis model using the clinical factors and qualitative CT features,a radiomics model using significant radiomic features,and a nomogram model combining all significant features,were built and compared in terms of receiver operating characteristic(ROC)curves.Decision curve analysis was performed for the nomogram model to explore its potential clinical benefit.Results:In addition to three visually-assessed qualitative imaging features,another three quantitative features selected from hundreds of radiomic features were found to be significantly(all P<0.05)associated with IPAs.The diagnostic nomogram model showed a significantly higher performance[area under the ROC curve(AUC)=0.903]in differentiating IPAs from non-IPAs than either the basis model(AUC=0.853,P=0.0009)or the radiomics model(AUC=0.769,P<0.0001).Decision curve analysis indicates a potential benefit of using such a nomogram model in clinical diagnosis.Conclusions:Quantitative radiomic features provide additional information over clinically-assessed qualitative features for differentiating IPAs from non-IPAs appearing as GGNs,and a diagnostic nomogram model including all these significant features may be clinically useful in preoperative strategy planning.

A correlation of computed tomography perfusion and histopathology in tumor edges of hepatocellular carcinoma

BACKGROUND： The peripheral morphologic characteristics of hepatocellular carcinoma （HCC） reflect tumor growth patterns. Computed tomography （CT） perfusion is a new method to analyze hemodynamic changes in tissues. We assessed the relationship between CT perfusion and histopathologic findings in the periphery of HCC lesions. METHODS： Non-contrast CT, enhanced dual-phase CT, and CT perfusion were performed on 77 subjects （47 patients and 30 controls）. Based on the imaging findings of enhanced dual- phase CT, the tumor edges were classified into three types： type Ⅰ （sharp）; type Ⅱ （blurry）; and type Ⅲ （mixed）. The CT perfusion parameters included hepatic blood flow, hepatic arterial fraction, hepatic arterial perfusion, and hepatic portal perfusion. The tissue sections from resected specimens were subjected to routine hematoxylin and eosin staining and immunohistochemical staining for CD34. The correlations between microvessel density （MVD） and the CT perfusion parameters were analyzed using Pearson＇s product-moment correlation coefficient. Changes in the perfusion parameters in tumor edges of different tumor types were evaluated. RESULTS： Type Ⅰ （sharp）： the pathologic findings showed fibrous connective tissue capsules in the tumor edges, and an MVD 〈30/ram2. Type Ⅱ （blurry）： the histology showed that the edges were clear with no capsules and an MVD 〉30/ram2. Type Ⅲ （mixed）： the pathology was similar to that of types I and II, and an MVD 〉30/mm~. Hepatic blood flow, hepatic arterial fraction, hepatic arterial perfusion, and hepatic portal perfusion were significantly increased in the tumor edges of HCC patients compared to those of the controls （P〈0.05）. The correlation between CT perfusion parameters and MVD was higher in blurry tumor edges of type II than in those of types Ⅰ or Ⅲ. CONCLUSION： CT perfusion imaging of tumor edges may be helpful in revealing histopathological features, and indirectly reflect angiogenic changes of HCCs.

Thrombosed prosthetic valve in Ebstein's anomaly:Evaluation with echocardiography and 64-slice cardiac computed tomography

Ebstein's anomaly(EA) is a rare cardiac congenital malformation with displacement of septal and posterior tricuspid leaflets,resulting in atrialization of the right ventricle.We report a case of EA in which the etiology of a malfunctioning prosthetic tricuspid valve is depicted on cardiac computed tomography to be as a result of thrombus lodged in the valve.

Three-dimensional visualization of soil pore structure using computed tomography

The geometric and spatial characteristics of pore structures determine the permeability and water retention of soils, which have important effects on soil functional diversity and ecological restoration. Until recently, there have not been tools and methods to visually and quantitatively describe the characteristics of soil pores. To solve this problem, this research reconstructs the geometry and spatial distribution of soil pores by the marching cubes method, texture mapping method and the ray casting method widely used in literature. The objectives were to explore an optimal method for three-dimensional visualization of soil pore structure by comparing the robustness of the three methods on soil CT images with single pore structure and porosity ranging from low (2–5%) to high (12–18%), and to evaluate the reconstruction performance of the three methods with different geometric features. The results demonstrate that there are aliases (jagged edges) and deficiency at the boundaries of the model reconstructed by the marching cubes method and pore volumes are smaller than the ground truth, whereas the results of the texture mapping method lack the details of pore structures. For all the soil images, the ray casting method is preferable since it better preserves the pore characteristics of the ground truth. Furthermore, the ray casting method produced the best soil pore model with higher rendering speed and lower memory consumption. Therefore, the ray casting method provides a more advanced method for visualization of pore structures and provides an optional technique for the study of the transport of moisture and the exchange of air in soil.

Temporal Trends in Radiation Dose Associated with Coronary Computed Tomography Angiography

Background: In 2010, the International Atomic Energy Agency launched the “3A’s campaign” as an effective tool for primary cancer prevention. In 2011, the American Association of Physicists in Medicine recommended the size specific dose estimate (SSDE). Objectives: To audit doses of Coronary CT Angiography (Coronary CTA) in tertiary care referral center. Methods: We reviewed 998 consecutive Coronary CTA (from 2007 to 2012). Doses (CTDIvol mGy), DLP (mGy*cm), effective dose (DLP*0.014, mSv) were on-line archived. SSDE was estimated retrospectively. Appropriateness score was evaluated for exams performed from the 2010. Results: Overall median dose per Coronary CTA was 49.7 mGy for CTDIvol, 55.5 mGy for SSDE, 994.96 mGy*cm for DLP, 13.9 mSv for effective dose. Median DLP decreased over time (1452.94 in 2007, 1605.56 in 2008, 1113.49 in 2009, 759.99 in 2010, 448.61 in 2011 and 497.88 mGy*cm in 2012, p < 0.0001). SSDE was proportional to the size dependent factor (SDF);in patients with SDF > 1 (88%) CTDIvol underestimated SSDE (48.49 vs 57.19 mGy), whilst in patients with SDF < 1 (12%) CTDIvol overestimated SSDE (56.46 vs 50.3 mGy). Scans were appropriate in 58%, uncertain in 24%, and inappropriate in 18% of cases. Doses were similar in appropriate, uncertain or inappropriate examinations and in excellent-to-good (81%) vs. sufficient-to-poor (19%) image quality exams. Conclusions: Coronary CTA reference doses can be very misleading. SSDE can allow individual technique optimization. The dose is similar in appropriate and inappropriate examinations, and unrelated to image quality. The rate of inappropriate examinations is still too high even after dissemination of guidelines.

Cosine fitting radiography and computed tomography

A new method in diffraction-enhanced imaging computed tomography （DEI-CT） that follows the idea developed by Chapman et al. [Chapman D, Thomlinson W, Johnston R E, Washburn D, Pisano E, Gmur N, Zhong Z, Menk R, Arfelli F and Sayers D 1997 Phys. Med. BioL 42 2015] in 1997 is proposed in this paper. Merged with a ＂reverse projections＂ algorithm, only two sets of projection datasets at two defined orientations of the analyzer crystal are needed to reconstruct the linear absorption coefficient, the decrement of the real part of the refractive index and the linear scattering coefficient of the sample. Not only does this method reduce the delivered dose to the sample without degrading the image quality, but, compared with the existing DEI-CT approaches, it simplifies data-acquisition procedures. Experimental results confirm the reliability of this new method for DEI-CT applications.

Utility of Spiral Computed Tomography in the Study of Dislocation of Cricoarytenoid Joint

The cricoarytenoid relationship presented with spiral computed tomography was demonstrated and the reconstruction of arytenoid dislocation was presented by using multiplanar reconstruction algorithms. Fifteen patients with arytenoid dislocation documented by fiberoptic laryngoscopy and strobovideolaryngoscopy and 10 normal persons were displayed by spiral computed tomography (CT). A making design of our own had been used to diagnose arytenoid dislocation on axial CT image. Results showed that dislocation of cricoarytenoid joint was consistently demonstrated on several of the overlapping thin axial reconstructions in each of the 15 patients, in whom asymmetry of the bilateral cricoarytenoid joints was noted on axial images. It was found that on the glottic-fissure level the basal angle on abnormal side was larger in 8 patients than that on the normal side and smaller in 7 patients in patient group, whereas right basal angle was equal to the left in 8 subjects, except 2 in control group. There was statistically significant difference in the number of the equal to two basal angles of glottic fissure between control group and patient group (P<0.025). High-quality sagittal and coronal reconstructive images often were helpful in confirming or clarifying the complex arytenoid orientations. The findings that two-side basal angle was not equal in triangle of glottic fissure can be used as an objective parameter to diagnose arytenoid dislocation. Spiral CT is a useful adjunct in the diagnosis and treatment of dislocation of cricoarytenoid joint.