Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

成人颅骨标本翼腭窝的CT表现

目的 在CT上测量翼腭窝的有关径值和孔距 ,并探讨翼腭窝的形态。方法 对 2 0个干颅上左右两侧的翼腭窝行CT横断与冠状扫描 ,测量并观察翼腭窝各扫描层面的有关径线和形态 ,对所得结果行统计学分析。结果 CT横断面上 ,翼腭窝上 1/ 4主要为凸面向后的双弧形 (88% ) ,其前后径与内外径最大值为 (6 .6± 2 .2 )mm和 (13 .7± 3.7)mm ;中 1/ 4主要表现为凸面相对的双弧形 (6 7% ) ,前后径与内外径最大值为 (6 .6± 2 .1)mm和 (12 .1± 2 .7)mm ;下 1/ 2全部表现为管形 ,直径为 (3.8± 1.7)mm。冠状面上翼腭窝上 1/ 4和中 1/ 4主要表现为斜的倒梯形(6 0 % ) ,余 40 %表现为斜的四边形 ,下 1/ 2全部表现为管形。圆孔位于眶下裂下方 (5 .2± 2 .3)mm处 ,翼管在圆孔内侧 (7.4± 2 .5 )mm和下方 (6 .2± 4.2 )mm。结论 翼腭窝形态多变 ,在不同层面可见到双弧形、波浪状、直弧形、弧直形、管形以及斜的倒梯形和斜的四边形 ;CT上采用合适窗宽和窗位 ,可对翼腭窝进行有关测量 ;根据所测翼腭窝各孔、裂间距 。

Review of radiographic findings in COVID-19

The purpose of this study is to review the published literature for the range ofradiographic findings present in patients suffering from coronavirus disease 2019infection. This novel corona virus is currently the cause of a worldwide pandemic.Pulmonary symptoms and signs dominate the clinical picture and radiologists arecalled upon to evaluate chest radiographs (CXR) and computed tomography (CT)images to assess for infiltrates and to define their extent, distribution andprogression. Multiple studies attempt to characterize the disease course bylooking at the timing of imaging relative to the onset of symptoms. In general,plain CXR show bilateral disease with a tendency toward the lung periphery andhave an appearance most consistent with viral pneumonia. Chest CT images aremost notable for showing bilateral and peripheral ground glass and consolidatedopacities and are marked by an absence of concomitant pulmonary nodules,cavitation, adenopathy and pleural effusions. Published literature mentioningorgan systems aside from pulmonary manifestations are relatively less common,yet present and are addressed in this review. Similarly, publications focusing onimaging modalities aside from CXR and chest CT are sparse in this evolving crisisand are likewise addressed in this review. The role of imaging is examined as it iscurrently being debated in the medical community, which is not at all surprisingconsidering the highly infectious nature of Severe Acute Respiratory Syndromecoronavirus 2.

Malignant giant cell tumor in the left upper arm soft tissue of an adolescent:A case report

BACKGROUND Giant cell tumor of soft tissue(GCT-ST)is an extremely rare low-grade soft tissue tumor that is originates in superficial tissue and rarely spreads deeper.GCT-ST has unpredictable behavior.It is mainly benign,but may sometimes become aggressive and potentially increase in size within a short period of time.CASE SUMMARY A 17-year-old man was suspected of having a fracture,based on radiography following left shoulder trauma.One month later,the swelling of the left shoulder continued to increase and the pain was obvious.Computed tomography(CT)revealed a soft tissue mass with strip-like calcifications in the left shoulder.The mass invaded the adjacent humerus and showed an insect-like area of destruction at the edge of the cortical bone of the upper humerus.The marrow cavity of the upper humerus was enlarged,and a soft tissue density was seen in the medullary cavity.Thoracic CT revealed multiple small nodules beneath the pleura of both lungs.A bone scan demonstrated increased activity in the left shoulder joint and proximal humerus.The mass showed mixed moderate hypointensity and hyperintensity on T1-weighted images,and mixed hyperintensity on T2-weighted fat-saturated images.The final diagnosis of GCT-ST was confirmed by pathology.CONCLUSION GCT-STs should be considered in the differential diagnosis of soft tissue tumors and monitored for large increases in size.

Role of Radiological Investigations of COVID-19 Patients with Pneumonia, Karachi Pakistan

The study was conducted to determine the role of radiological investigation in assessing the severity of COVID-19 pneumonia with the help of chest X-ray (CXR), high resolution computed tomography (HRCT), and ultrasound. This was a retrospective study conducted on 105 COVID-19 patients with symptoms of fever, cough, dyspnea, loss of sense of smell and taste, body ache. Diagnostic tests PCR were positive for COVID-19 included from Medicare Cardiac and General Hospital and Jinnah Medical College Hospital Korangi (JMCH) from April to November 2020. Written informed consent was taken from all participants. This study was approved by ethical review committee, Jinnah Medical & Dental College. Real time-PCR (RT-PCR) was done for the confirmation. Radiological imaging including Chest X-ray, HRCT chest, and ultrasound was done to study the severity of symptoms. Sixty-five patients had mild to moderate symptoms with oxygen saturation between 96% - 98% and 30 patients with severe pneumonia had between saturation 50% - 55%. Patients with mild symptoms were followed up by chest X-ray showing mostly normal chest X-rays but single or patches of ground glass opacities (HRCT). HRCT of 10 patients with low oxygen saturation 50% were already done showing bilateral peripheral patchy consolidation predominantly involving mid and lower lobes. 3 patients presented with patchy lung opacities and ultrasound showing similar findings with pleural effusion and ascites. Radiological imaging, specially CT-Scan was highly significant for diagnosing COVID-19 and severity of infection even in patients with negative PCR. Chest X-ray and ultrasound were also found to be a very useful tool.

Cerebral artery evaluation of dual energy CT angiography with dual source CT

Background Conventional computed tomography angiography （CTA） is time consuming, user-dependent and has poor image quality in skull base region. This study assessed the feasibility of a new method, dual energy CTA for depicting the cerebral artery.Methods Phantom scan was done with head CTA sequences on dual source CT and 64 spiral CT for radiation dose calculation. Dual energy CTA was done with dual source CT on 36 patients who were suspected of having cerebral vascular disease. Three series axial images in 0.75 mm thick, 0.4 mm increment were acquired, which were named with 80 kV, 140 kV and merged images; 80 kV and 140 kV images were transferred into dual energy software, and maximum intensity projection （MIP） image was generated quickly by dual energy bone remove （DEBR group）; merged images were transferred into In Space software to acquire MIP image through manual conventional bone remove （CoBR group）. Post processing time and reading time were compared. Image qualities of the two groups were compared, mainly focusing on skull base segments of internal carotid artery and bone subtraction. ANOVA and SNK tests were applied for radiation dose comparison. Student＇s t test and Wilcoxon rank sum test were applied for assessing differences between data for significance. Cohen＇s kappa was used for interobserver agreement. Results Radiation dose of phantom scan showed dual energy CTA was between digital bone subtraction and conventional CTA. The post processing time and reading time were much shorter in DEBR than CoBR, and image quality in skull base was much higher in DEBR than CoBR （P〈0.01）. There was no significant difference for suprasellar vessels between two groups （P〉0.5）. Interobserver agreement for all vessel segments was excellent （kappa=0.97）. Conclusions Dual energy CTA is a reliable, new modality for depicting cerebral artery, overcoming the limitation of conventional CTA in the skull base region. It can save much time in post processing and reading than conventional CTA.

LIMITED TOMOGRAPHY RECONSTRUCTION VIA TIGHT FRAME AND SIMULTANEOUS SINOGRAM EXTRAPOLATION

X-ray computed tomography （CT） is one of widely used diagnostic tools for medical and dental tomographic imaging of the human body. However, the standard filtered back- projection reconstruction method requires the complete knowledge of the projection data. In the case of limited data, the inverse problem of CT becomes more ill-posed, which makes the reconstructed image deteriorated by the artifacts. In this paper, we consider two dimensional CT reconstruction using the projections truncated along the spatial direc- tion in the Radon domain. Over the decades, the numerous results including the sparsity model based approach has enabled the reconstruction of the image inside the region of interest （ROI） from the limited knowledge of the data. However, unlike these existing methods, we try to reconstruct the entire CT image from the limited knowledge of the sinogram via the tight frame regularization and the simultaneous sinogram extrapolation. Our proposed model shows more promising numerical simulation results compared with the existing sparsity model based approach.