Fatigue properties and damage constitutive model of salt rock based on CT scanning

To investigate the macroscopic fatigue properties and the mesoscopic pore evolution characteristics of salt rock under cyclic loading,fatigue tests under different upper-limit stresses were carried out on salt rock,and the mesoscopic pore structures of salt rock before and after fatigue tests and under different cycle numbers were measured using CT scanning instrument.Based on the test results,the effects of the cycle number and the upper-limit stress on the evolution of cracks,pore morphology,pore number,pore volume,pore size,plane porosity,and volume porosity of salt rock were analyzed.The failure path of salt rock specimens under cyclic loading was analyzed using the distribution law of plane porosity.The damage variable of salt rock under cyclic loading was defined on basis of the variation of volume porosity with cycle number.In order to describe the fatigue deformation behavior of salt rock under cyclic loading,the nonlinear Burgers damage constitutive model was further established.The results show that the model established can better reflect the whole development process of fatigue deformation of salt rock under cyclic loading.

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.

Optimum Threshold Estimation of Thorax CT Scan for COVID-19 Diagnosis in a Single Center in Cameroon

Objective: To evaluate the lung CT scan as a possible predictive diagnostic method for COVID-19 in the Cameroonian context. Methods: We designed a cross sectional study. Suspected cases of COVID-19 during the first wave at the national social insurance fund (NSIF) hospital were screened with both COVID-19 with lung CT scan and a PCR test. Univariate analysis was performed for sample description and multivariate analysis to assess the correlation between positive results for the PCR and other parameters. We estimated the optimum threshold of sensitivity/specificity, and area under curve using the empirical method and package. Results: A total of 62 suspected COVID-19 cases were recorded, predominantly males (Sex Ratio = 2.2) with a median age of 58.5 (IQR = 19.7). Among our 62 patients, 29 (46.8%) were confirmed COVID-19 cases with positive PCR results. All the patients had a thorax CT scan with a median impairment of 40% (IQR = 20%). The optimum threshold estimate for CT scan for COVID-19 infection diagnosis was 60% (95% CI = 25% - 80%). Overall, the sensitivity and specificity estimates were 0.30 (95% CI = 0.15 - 0.49) and 0.87 (95% CI = 0.70 - 0.96), respectively, leading to an Area Under Curve (AUC) estimate of 0.59 (95% CI = 0.46, 0.71). Conclusion: In this setting, lung CT scan was neither sensitive nor specific to predict COVID-19 disease.

Quantitative investigation of multi-fracture morphology during TPDF through true tri-axial fracturing experiments and CT scanning

Due to the reservoir heterogeneity and the stress shadow effect, multiple hydraulic fractures within one fracturing segment cannot be initiated simultaneously and propagate evenly, which will cause a low effectiveness of reservoir stimulation. Temporary plugging and diverting fracturing(TPDF) is considered to be a potential uniform-stimulation method for creating multiple fractures simultaneously in the oilfield. However, the multi-fracture propagation morphology during TPDF is not clear now. The purpose of this study is to quantitatively investigate the multi-fracture propagation morphology during TPDF through true tri-axial fracturing experiments and CT scanning. Critical parameters such as fracture spacing, number of perforation clusters, the viscosity of fracturing fluid, and the in-situ stress have been investigated. The fracture geometry before and after diversion have been quantitively analyzed based on the two-dimensional CT slices and three-dimensional reconstruction method. The main conclusions are as follows:(1) When injecting the high viscosity fluid or perforating at the location with low in-situ stress, multiple hydraulic fractures would simultaneously propagate. Otherwise, only one hydraulic fracture was created during the initial fracturing stage(IFS) for most tests.(2) The perforation cluster effectiveness(PCE) has increased from 26.62% during the IFS to 88.86% after using diverters.(3) The diverted fracture volume has no apparent correlation with the pressure peak and peak frequency during the diversion fracturing stage(DFS) but is positively correlated with water-work.(4) Four types of plugging behavior in shale could be controlled by adjusting the diverter recipe and diverter injection time, and the plugging behavior includes plugging the natural fracture in the wellbore, plugging the previous hydraulic fractures, plugging the fracture tip and plugging the bedding.

CT Scan of the Foot in Patients with Chronic Non-Healing Diabetic Foot Ulcer

Background: Diabetes mellitus is a chronic disease where there is an increased blood sugar level in the body which is either caused due to inability of the pancreas to secrete insulin or the body’s inability to utilize it. The prevalence of diabetes mellitus is growing rapidly worldwide. Statistics show that in the year 2014, there were a total of 422 million cases of DM. Diabetes mellitus is a major cause of heart attacks, kidney failure, blindness and leg amputations. Diabetic foot ulcers are quite common and are estimated to affect nearly 15% of all diabetic patients during their lifetime. In long standing diabetic patients with chronic non-healing ulcers, bony changes or deformities are not uncommon. These bony changes can be identified using CT scans. Materials and Methods: An observational study was conducted on a total of 40 patients with chronic non-healing ulcer attending the surgery outpatient department of Saveetha Medical College, Chennai, Tamilnadu. The CT-scans of their foot were observed for deformities or bony changes. Results: Out of 40 patients, 67.5% were males and 32.5% were females. A maximum number of subjects fell under the age group of 51 - 60 years. The most common site of the ulcer was found to be in the plantar surface of big toe (53%). Among the 40 patients, 33 of them were found to have bony abnormalities on the CT scan of foot and no apparent changes were seen in the rest. Bone erosions (35%), osteopenic changes (22.5%), Charcot’s joint (2.5%), osteophyte formation (12.5) and reduced joint space (10%) were the predominant changes observed on the CT scans of the study population.

CT Scans and Delays in Diagnosis of Stroke in Senegal’s Regional Hospitals: A Multicenter Study of 655 Cases

Stroke represents the 2nd cause of mortality and 1st cause of physical disability in the adult population. In Senegal, it represents 30% of hospitalization and 2/3 of the mortality in the department of neurology in the capital city, Dakar. Objective: To specify the types of stroke and to evaluate diagnostic delays in Senegal’s regional hospitals. Materials and Methods: This was a retrospective, cross-sectional, descriptive, multicentric study for 4 years (from 2014 to 2017) including any patient presenting a clinical suspicion with a CT scan confirmation of stroke in one of the 9 regional hospitals in Senegal with a recruitment period of 6 months per hospital. CT scans were performed with a 16 slices machine in 6 hospitals, 4 slices in 2 hospitals and 2 slices in 1 hospital. We studied the types and location of strokes, the associated signs and the time from stroke onset to admission and the time from admission to CT scan. Results: 655 patients were retained including 322 men and 333 women for an M/F ratio of 0.96. The average age was 63 years (range: 7 years, 112 years). High blood pressure was noted in 59.2% of patients and diabetes in 10.7% of patients. Strokes were ischemic in 76% of cases involving the middle cerebral artery in 73% of cases and hemorrhagic in 24%, of which 80.7% were deep localized. A mass effect was noted in 7.5% of cases, an engagement in 6.9% of cases and ventricular hemorrhage in 2.7% of cases. The delay between the onset of the deficit and admission was less than 6 hours in 10.6% of patients. The time between the onset of stroke and admission to hospital was specified in 416 patients (63.5%) of the study population, it was less than 6 hours in 10.6% of patients, between 6 hours and 24 hours for 29.3% and more than 24 hours for 60.1%. Between admission and the CT scan, the time was precise in 459 patients (70%), it was less than 6 hours in 37.9%, between 6 hours and 24 hours in 43.6 % and more than 24 hours in 18.5%. Conclusion: CT is central to the diagnosis of stroke in rural areas. However, there is a significant delay in diagnosis and management.

Evaluation of CT Scans Reports in Pancreatic Tumors at Ouagadougou (Burkina Faso)

Background: There are no recommendations for the use of standardised CT reports in oncology in our country. The aim of this study was to evaluate CT reports of pancreatic tumors in the city of Ouagadougou. Materials and Methods: Descriptive, multicenter, cross-sectional study conducted from 1st January 2013 to 31 December 2021. It concerned CT scan reports from five public and private imaging centers in the city of Ouagadougou. During the study period, 41 reports of pancreatic tumors were collected. We evaluated the reports using the standardized model developed by the Society of Abdominal Radiology and the American Pancreatic Association as a reference. Results: CT scan reports were not standardised. The writing style was free. Concerning the lesion, the aspect of the tumor at the pancreatic time was the item with the least information (24.4%). The status of the superior mesenteric artery was mentioned in 17%, the celiac trunk and the portal trunk in 12.2% of cases and 9.7% for the superior mesenteric vein. No report noted the appearance of the common hepatic artery. The status of the lymph nodes, liver and peritoneal cavity was mentioned in all reports. The exact location of the lymph nodes was not specified. The analysis of the reports classified them into two groups: potentially resectable tumours in the absence of secondary locations in 31.7% of cases and locally advanced tumours or presence of metastases in 68.3% of cases. Conclusion: The CT reports were not standardized. The items allowing evaluating the loco-regional extension of the tumor were the least specified. This may suggest the high rate of potentially resectable tumours in our study.

A Simple Computational Approach for the Texture Analysis of CT Scan Images Using Orthogonal Moments

This paper is a study on texture analysis of Computer Tomography (CT) liver images using orthogonal moment features. Orthogonal moments are used as image feature representation in many applications like invariant pattern recognition of images. Orthogonal moments are proposed here for the diagnosis of any abnormalities on the CT images. The objective of the proposed work is to carry out the comparative study of the performance of orthogonal moments like Zernike, Racah and Legendre moments for the detection of abnormal tissue on CT liver images. The Region of Interest (ROI) based segmentation and watershed segmentation are applied to the input image and the features are extracted with the orthogonal moments and analyses are made with the combination of orthogonal moment with segmentation that provides better accuracy while detecting the tumor. This computational model is tested with many inputs and the performance of the orthogonal moments with segmentation for the texture analysis of CT scan images is computed and compared.

The application of CT scan in Nuss procedure for pectus excavatum

Objective To study the application CT scans in Nuss procedure for pectus excavatum. Methods 648 children with pectus excavatum underwent Nuss procedure from July 2002 to September 2008. The preoperative CT scan was carried out for evaluation of the deformity degree and morphology classification of chest wall malformation,

Early Detection of Lung Cancer Using CT Scan and Bronchoscopy in a High Risk Population

Background: Computed tomography (CT) and bronchoscopy have been shown to improve the detection rates of peripheral and central lung cancers (LC), respectively. However, the performance of the combination of CT and bronchoscopy in detecting LC, in high-risk patients, is not clear. Patients & Methods: This prospective study included 205 high-risk patients with a history of at least 2 of the following risk factors: (1) heavy smoking;(2) aero-digestive cancer;(3) pulmonary asbestosis or;(4) chronic obstructive pulmonary disease. Patients were offered chest X-ray, sputum cytology, conventional white-light followed by autofluorescence beonchoscopy (WL/AFB) and low-dose spiral CT both at baseline and follow-up visits. Results: Seven patients (3.4%) were diagnosed with LC or carcinoma in-situ (CIS) at baseline: CT evaluation detected 5 LC/CIS, while WL/AFB evaluation also identified 5 LC/CIS, 2 of which were not detected on CT. Six (85%) of these baseline lesions were early stage (0/IA). The relative-sensitivity of CT with WL/ AFB was 40% better than CT alone. On four year follow-up, 20 patients (9.8%) were diagnosed with an LC/CIS. CT with WL/AFB detected 19 cases (95%), whereas CT alone detected 15 cases (75%). Conclusion: Bimodality surveillance with spiral CT and WL/AFB can improve the detection of early stage LCs among high-risk

Relevance of Chest CT Scan Requests in Two University Teaching Hospitals in a Developing Country

Chest investigation is common in hospital practice. Chest X-ray is readily available and usually the first chest investigation. Thoracic CT scan constitutes an alternative and complimentary chest investigation. It is currently the most efficient investigation for the chest and its contents. Objectives: To evaluate the relevance of chest CT Scan requests in two university teaching hospitals in Cameroon. Material and Methods: We conducted a cross-sectional, retrospective and descriptive study at the Radiology and imaging units of the Yaounde Central Hospital and the Yaounde University Teaching Hospital Centre. Included in our study were files of patients who had a chest CT scan investigation during three years. Results: We had a study population of 323 subjects. The age interval was 23 months to 91 years old. Pulmonologist were the most prescribers with 27.2%. We had 80% conformity of indications with French Society of Radiology (FSR) standards. 50 over of 323 indications were not recommended by the FSR. Conclusion: There is a conformity rate of 80% between indications and the FSR recommendations.

Porosity Estimation from High Resolution CT SCAN Images of Rock Samples by Using Housfield Unit

Computer Automated Tomography has been shown to be a valuable tool in production research because it provides a non-destructive method to identify and evaluate the internal structural characteristics of reservoir rock. In CT scan, Hounsfield Unit (HU) is proportional to the degree of X-ray attenuation by the tissue. The aim of the present study was to introduce the method to estimate porosity which is one of physical parameters of reservoir rock though HU data. In this study, an Image J software was used to extract Hounsfield Unit data and calibrate by standard material’s density. This method provides the ability of using CT Scanner in advanced reservoir characterization and flow test experiments.

Anatomic Variants of Sphenoid Sinuses and Adjacent Structures: A Study of 225 Skull CT Scans at CNHU-HKM in Benin, West Africa

Objective: This study aimed to describe anatomic variants of sphenoidal sinuses and adjacent structures. Methods: A retrospective and descriptive study was carried out at The National and University Teaching Hospital Hubert Koutoukou Maga (CNHU-HKM), of Cotonou in Benin from November 1st to December 31st. A review of CT scans skull was done for the subjects aged at least 16 years old. Anatomic variants of the sphenoid sinuses and adjacent structures have been investigated. Results: 225 CT scans of skull were analyzed. The sellar type was the most common type of pneumatization of sphenoid sinuses (74.7%). Pneumatization of anterior clinoid processes of greater and lesser wings of the sphenoid and of pterygoid processes was observed in 7.1%;4.6%;3.3% and 7.3%;respectively. Protrusion of carotid canals and optic canals, maxillary and vidian nerves were observed in 48.3%;13.1%;18% and 9.5%;respectively. Conclusion: Risky anatomic variants of the sphenoid sinuses and adjacent structures are also described by CT-scan among Beninese. Before any surgery and to avoid bad outcome, a precise approach of these risky anatomic variants must be carried out by using CT-scan.

An Assessment of Both Patients and Medical Staff Awareness of the Risks of Ionizing Radiation from CT Scan in Cameroon

Objectives: To assess the patients and health personnel’s level of awareness on risks related to ionizing radiation during CT scan. Materials and methods: Three questionnaires were addressed to patients, prescribing physicians, and the medical imaging staff for three hospitals respectively. This permitted us to assess their knowledge on the benefits and risks of the required medical exam, based on the dangers of being exposed to X-rays, especially induced-radiation cancer following the amount of X-rays received during a CT scan and the possibility of not receiving radiation as tools of diagnosis. Results: 150 patients, 84 referring doctors of CT scan tests and 60 medical imaging personnel were retained. For patients, only 7.1% received information on the benefits and risks of their exams, and 34.4% believed that x-rays were harmful to their health. For the prescribers, 46.7% took into account the benefits/risk ratio before prescribing a test and only 16.7% of the referring doctors have informed the patient of the risks related to X-ray. 90% of the medical imaging staff ensures that the required test is justified, and 50% informed the patient on the risks associated with their radiation exposure, and the increased risk of developing cancer. 65% of the imaging staff could not estimate the dose that the patient will receive during the medical test. 25% mentioned the dose received during the acquisition in the patient’s exam report. Conclusion: This study confirms that the referring doctors, the patients, and the radiologists have a low knowledge concerning the risks associated with radiation exposure during a CT scan assessment. We will therefore say that patients and prescribers are not aware of the doses of radiation on CT and their possible risks, even though there is a risk of developing cancer.

Evaluation of the Knowledge of CT Scan Prescribers on Patients’ Radioprotection in Senegal

Medical imaging has enabled major improvements in the medical care of the patient. However, some of these tests have the disadvantage of using ionizing radiation at low doses. Although the CT scan is a powerful diagnostic tool, it remains a highly radiant imaging modality. In addition, the risk of radiation-induced cancer associated with low X-ray doses is established by the American Phase 2 study BEIR VII, and preventive measures require a good level of knowledge on radioprotection by imaging test prescribers. In our study, we evaluated the knowledge of CT scan prescribers in Senegal regarding patient radioprotection. These prescribers consisted of physicians and surgeons without distinction of specialty. Our objective was to have the required data for optimizing CT prescriptions in compliance with the principles of radioprotection. Our work focused on a descriptive analytical study of 107 doctors who prescribed CT scan in public health institutions in Senegal. Our results revealed poor knowledge of doctors prescribing CT scan on induced radio risks, even though the majority of them stated that they took those risks into account. Our data were not isolated, they were applicable to similar studies conducted outside Senegal. In summary, our study led on the one hand to recommendations on initial and continuing training and on the other hand on organizational and regulatory considerations.

Correlation Study between Skeletal Scintigraphy and CT Scan in Diagnosing Bone Metastases

A retrospective study for 98 patient suspected to bone scan at department of radiology take place, to find out which imaging modality is more sensitive between computed tomography (CT) and bone scan;age group of patient was from 1 year to 90 year, the highest Site of Metastases for both Bone scan & CT was at vertebra with 31%, and the positive finding was also 31% for bone scan, while for CT the highest Site of Metastases was at forearm with 34%, and the sensitivity for CT was 44%, and 56% for bone scan. The study recommends that patients with bone metastases are kindly recommended to bone scan investigation rather than CT scan.

Comparison of the diagnostic accuracy of CT scan with oral and intravenous contrast versus CT scan with intravenous contrast alone in the diagnosis of blunt abdominal trauma

Purpose:Abdominal CT scan using oral and intravenous(IV)contrast is helpful in the diagnosis of intra-abdominal injuries.However,the use of oral and IV contrast delays the process of diagnosis and increases the risk of aspiration.It has also been shown that CT scan with IV contrast alone is as helpful as CT scan with oral and IV contrast and rectal CT scan in detecting abdominal injuries.Therefore,the present study aims to prospectively compare the diagnostic value of CT scan with oral and IV contrast versus CT scan with IV contrast alone in the diagnosis of blunt abdominal trauma(BAT).Methods:Altogether 123 BAT patients,60(48.8%)women and 63(51.2%)men with the mean age of(40.4±18.7)years who referred to the emergency department of Imam Khomeini Educational and Medical Center in Sari,Iran(a tertiary trauma center in north of Iran)from November 2014 to March 2017 and underwent abdominal CT scans+laparotomy were investigated.Those with penetrating trauma or hemodynamically unstable patients were excluded.The participants were randomly allocated to two groups:abdominal CT scan with oral and IV contrast(n=63)and CT scan with IV contrast alone(n=60).No statistically significant difference was found between two groups regarding the hemodynamic parameters,age,gender,injury mechanisms(all p>0.05).The results of CT scan were compared with that of laparotomy results.The collected data were recorded in SPSS version 22.0 for Windows.Quantitative data were presented as mean and SD.Results:The sensitivity and specificity of CT scan using oral and IV contrast in the diagnosis of BAT were estimated at 96.48(95%CI:90.73-99.92)and 92.67(95% CI:89.65-94.88),respectively;while CT scan with IV contrast alone achieved a comparable sensitivity and specificity of 96.6(95% CI:87.45-99),42 and 92.84(95% CI:89.88-95.00),respectively.Conclusion:CT scan with IV contrast alone can be used to assess visceral injuries in BAT patients with normal hemodynamics to avoid diagnostic delay.

基于CT技术的黄原胶加固土干湿循环条件下力学性能和微观结构劣化机制研究

干湿循环对岩土体的工程特性具有重要影响。采用CT扫描技术和力学测试,对加入不同含量黄原胶(0%,0.5%,1.5%)加固的黏土在经历不同次数(0,1,4,8,12次)干湿循环作用下的力学性能和微观结构劣化机制进行了研究,得到结论:(1)黄原胶能够有效提高土体的抗压强度和耐干湿循环效果。随着黄原胶含量的增加,干湿循环作用后的强度损失逐渐减小,当循环次数从0次增加到4次时,对于加入黄原胶含量分别为0%,0.5%,1.5%的试样,抗压强度分别损失了42.75%,17.2%,14.04%。(2)加固土的抗压强度与干湿循环次数之间保持指数下降的关系,当循环次数达到4次后,随着循环次数的进一步增加,抗压强度和弹性模量均在较小的变化范围内波动。(3)随着干湿循环次数的增加,黄原胶加固土的孔隙率表现出先增加后减小的趋势,连通孔隙不断扩展,而孤立孔隙表现出先增加后减小的趋势。(4)随着试样的干燥,黄原胶在土颗粒间形成网状基质,提高土体的强度和耐干湿循环能力。

基于CT断层扫描的木质家具与原木内部缺损三维可视化研究

研究木质家具与原木试件内部缺损三维可视化,有助于木质文物精准干预性保护与木材高效规划利用。凸显三维成像技术可视化优势,对木质文物保护具有重要意义。本文采用philips16排CT——A机型Brilliace16对试件三维断层扫描。通过对CT扫描后原始图像的分割,获取品质较佳的三维数字模型。继而对分割后的图像进行切面与断面两个维度的手工着色,随后通过三维重建可得到开裂、虫洞、朽坏等不同形式缺损的三维形态,并可得到与之对应的精准三维模型。试验证明:通过三维重建,可获取木质试件内部不同类型三维缺损形态的可视化分析,可对缺损形态进行360°观察,并可获取三维缺损形态的表面积、体积等精准物理参数。本技术可为木质文物修复提供三维缺损形态的精准参数及直观可视化三维模型。

基于CT扫描受压注浆体试块三维孔裂隙结构参数表征

目的为研究注浆体试块单轴压缩过程中孔裂隙结构演化特征,方法以级配砂砾注浆体试块为研究对象,对其单轴压缩过程分阶段进行工业CT扫描,并采用AVIZO对CT切片进行分析,重构孔裂隙结构三维模型,定量表征孔裂隙与孔喉特征参数。结果结果表明:单轴压缩下,试块依次经历孔裂隙萌生、发育、扩展与贯通阶段,孔裂隙演化特征比较明显,萌生阶段孔隙数增幅为14.41%,无明显贯通;发育阶段孔隙数增加326.91%,伴有一定数目孔隙贯通;扩展阶段孔隙数减少了57.79%,孔隙等效直径最大值增幅为223.45%,大部分孔隙贯通为裂隙;贯通阶段孔裂隙数目几乎不变,孔隙等效直径最大值增幅为92.83%,裂隙贯通后形成多个破裂面。峰值后试块出现连通孔隙,该阶段注浆体孔隙与喉道发育完全,试块破坏。结论研究结果可为后续破碎岩石注浆工程实践提供参考。