Nonlinear flow behavior of fluids through three-dimensional(3D)discrete fracture networks(DFNs)considering effects of fracture number,surface roughness and fracture aperture was experimentally and numerically investig...Nonlinear flow behavior of fluids through three-dimensional(3D)discrete fracture networks(DFNs)considering effects of fracture number,surface roughness and fracture aperture was experimentally and numerically investigated.Three physical models of DFNs were 3D-printed and then computed tomography(CT)-scanned to obtain the specific geometry of fractures.The validity of numerically simulating the fluid flow through DFNs was verified via comparison with flow tests on the 3D-printed models.A parametric study was then implemented to establish quantitative relations between the coefficients/parameters in Forchheimer’s law and geometrical parameters.The results showed that the 3D-printing technique can well reproduce the geometry of single fractures with less precision when preparing complex fracture networks,numerical modeling precision of which can be improved via CT-scanning as evidenced by the well fitted results between fluid flow tests and numerical simulations using CT-scanned digital models.Streamlines in DFNs become increasingly tortuous as the fracture number and roughness increase,resulting in stronger inertial effects and greater curvatures of hydraulic pressure-low rate relations,which can be well characterized by the Forchheimer’s law.The critical hydraulic gradient for the onset of nonlinear flow decreases with the increasing aperture,fracture number and roughness,following a power function.The increases in fracture aperture and number provide more paths for fluid flow,increasing both the viscous and inertial permeabilities.The value of the inertial permeability is approximately four orders of magnitude greater than the viscous permeability,following a power function with an exponent a of 3,and a proportional coefficient b mathematically correlated with the geometrical parameters.展开更多
Theaim of the present work wasto analyze moisture flow and moisture content data for high-temperature drying by usingan advanced image- processing algorithm.Since wood starts to shrink below the fibre saturation point...Theaim of the present work wasto analyze moisture flow and moisture content data for high-temperature drying by usingan advanced image- processing algorithm.Since wood starts to shrink below the fibre saturation point during drying, the size and shape of wood will change. The dry wood image was thoroughly transformed to the shape of the wet wood image prior to calculating the dry weight moisture content. The use of the image- processing algorithm for the dry weight moisture content on density data from the CT-scanning during drying in a controlled high-temperature environment showed that this method is a powerful tool for analyzing the moisture flow inside the wood piece. Furthermore, the new CT-scanner together with the climate chamber gave unique results, as it has not been possible to study high-temperature drying with this method before.展开更多
Brain malformations are rare, difficult to diagnose and have unpredictable evolution. They are the major causes of epilepsy, psychomotor development abnormalities and other neurological disorders. The neuroimaging tec...Brain malformations are rare, difficult to diagnose and have unpredictable evolution. They are the major causes of epilepsy, psychomotor development abnormalities and other neurological disorders. The neuroimaging technique of choice for diagnosis of these malformations is magnetic resonance imaging (MRI), but unfortunately MRI is expensive, and is not available in a poor resource country like Cameroon. CT scan associated to clinical signs can help to suspect or to confirm a malformation. The authors report here three cases of malformations discovered during cranial CT scan at the regional hospital of Ngaoundéré. They are Dandy Walker malformation, Sturge Weber’s disease and hemimegalencephaly. These cases contribute to the knowledge of this rare event, and emphasize the importance of CT scan on their diagnosis in the absence of MRI.展开更多
Purpose: Despite irradiation, CT-scan remains an important diagnostic tool in epilepsy in poor countries where MRI is neither available nor affordable. But many causes of epilepsy are not accessible to CT-scan and thi...Purpose: Despite irradiation, CT-scan remains an important diagnostic tool in epilepsy in poor countries where MRI is neither available nor affordable. But many causes of epilepsy are not accessible to CT-scan and this technique remains expensive for many poor families in countries with limited resources. The aim of this study was to determine clinical or electroencephalogram variables which could predict brain CT-scan abnormalities in childhood epilepsy. Methods: It was a cross-sectional study including 151 epileptic children who underwent head CT-scan from October 2011 to march 2012, in one university-affiliated hospital in Cameroon (YGOPH). The data collected were clinical, type of seizure, Electroencephalogram and head CT-scans results. Independent predictive factors for CT abnormalities were sought by logistic regression. A p value : Of the 151 children, 54.3% (82/151) were boys (sex ratio: 1.18 M/1F). The median age was 54 months [2 - 190 months];74.8% of children were more than 2 years old but at the onset of epilepsy they were 2 years old or less. Birth asphyxia, mental retardation and neurologic deficit were respectively associated in 62.4%, 54.3% and 51.7% of cases. Eighty-five had focal epilepsy (56.3%), 61.6% had abnormal head CT-scan, 68.9% had abnormal EEG, with no significant gender difference. The factors most significantly associated with abnormal head CT-scan were: child age ≤ 2 years, maternal hypertension/eclampsy, cerebral palsy, and child microcephaly, with 89% to 92% abnormal CT. The two independent predictors of abnormal CT were patients’ age ≤ 2 years and microcephaly. The two main CT-scan lesions were cerebral atrophy (28.5%) and brain infarct (16.6%). None of these abnormalities was correlated to any type of epilepsy. Conclusion: Almost two-thirds of head CT-scan performed in epileptic children are abnormal in our setting. Patients of 2 years old or less and those with microcephaly are very likely to have brain anomalies on CT-scan. The most common brain lesions are atrophy, cerebral infarction and porencephalic cavities. Action to reduce birth asphyxia may lead to the reduction of the incidence of epilepsy in children.展开更多
Background: Detection of malignant liver mass is very important for the treatment modalities. Objective: The purpose of the present study was to establish the usefulness of CT scan in the diagnosis of malignant hepati...Background: Detection of malignant liver mass is very important for the treatment modalities. Objective: The purpose of the present study was to establish the usefulness of CT scan in the diagnosis of malignant hepatic mass. Methodology: This cross sectional study was carried out in the Department of Radiology and Imaging at Mymensingh Medical College Hospital (MMCH), Mymensingh, Banghabandhu Sheikh Mujib Medical University (BSMMU), Dhaka and Dhaka Medical College Hospital (DMCH), Dhaka during the period of 1st January 2006 to 31st December 2007. Patients admitted in the Department of Medicine and Department of Hepatobiliary of MMCH, BSMMU, and DMCH with the clinical diagnosis of fever, abdominal pain, anorexia, nausea/vomiting, loss of appetite, jaundice, weight loss and ascites were selected as study population. CT scan and histopathology were performed to all the patients. Result: A total number of 50 patients were recruited for this study. Mean age of all patients was 51.28 ± 14 years with a range of 17 year to 78 years. Among all patients 28 had multiple lesion, of them 71.4% was malignant and 28.6% was benign. On the other side 22 patients had solitary lesion, of them 36.4% was malignant and 63.6% was benign展开更多
Background: CT-scan is a very useful diagnostic tool for the detection of hepatic mass. Objective: The present study was undertaken to determine the CT-scan findings of benign and malignant hepatic mass patients. Meth...Background: CT-scan is a very useful diagnostic tool for the detection of hepatic mass. Objective: The present study was undertaken to determine the CT-scan findings of benign and malignant hepatic mass patients. Methodology: This was a cross sectional study conducted in Radiology and Imaging Department at Mymensingh Medical College Hospital (MMCH), Mymensingh;Dhaka Medical College Hospital (DMCH), Dhaka and Banghabandhu Sheikh Mujib Medical University (BSMMU), Dhaka with the collaboration of Pathology Department of the same institute for histopathological confirmation. This study was carried out from January 2006 to December 2007 for a period of 2 years. The patients who were clinically suspected of having hepatic mass attended in the Radiology and Imaging Department in the above mentioned institutes were included as study population. All the CT-scan findings were recorded. Result: A total number of 50 patients were enrolled for this study. CT-scan was done among 40 males and 10 females with a mean age of 51.28 years old. Hypodensity was found in 17 (60.7%) and 18 (81.8%) cases in malignant and benign hepatic lesions respectively. Ill-defined margin was detected in 12 (42.9%) and 6 (27.3%) cases respectively. Calcification was present on 11 (39.3%) malignant lesion and 6 (27.3%) benign lesions. Pressure effect on biliary apparatus was found in 11 (39.3%) malignant lesions and 1 (4.5%) benign lesions (p < 0.05). Lymphadenopathy was found in 10 (35.7%) malignant lesions and 1 (4.5%) benign lesions (p < 0.05). Conclusion: In conclusion, CT-scan findings of malignant and benign hepatic mass show hypodensity with more contrast enhancement in malignant lesions with more calcification in malignant lesion;however, significant difference is detected in pressure effect on biliary apparatus and lymphadenopathy.展开更多
Introduction: Cranial trauma is a serious medico-surgical pathology that hinders the vital and functional prognosis. The Rotterdam computed tomography (CT) score refined features of the Marshall score. This score was ...Introduction: Cranial trauma is a serious medico-surgical pathology that hinders the vital and functional prognosis. The Rotterdam computed tomography (CT) score refined features of the Marshall score. This score was designed to categorize traumatic brain injury (TBI) type and severity in adults. The aim of our research was to evaluate the association between the Rotterdam CT scores of patients after a cranial traumatism in terms of survival. Material and methods: It was a cross-sectional and analytical study from January 2018 to March 2020, using medical records of patients suffering from cranial traumatism, received and taken in charge in the Yaounde central hospital. Results: 100 patients were retained out of 115 recruited patients. The average age was 35.20 with a sex ratio of 4.55. The Rotterdam score was between 1 and 5 with a median of 2. The overall mortality at 6 months and 1 year was 32%. With an equal score compared to European studies, we recorded significantly higher mortality. We found the sequelae in 24% of the patients. GOS ranged from 1 to 5, and survival without sequelae (GOS 1) was the most represented. There was a positive correlation between the Rotterdam score and the GOS with a Pearson correlation coefficient of +0.514. Conclusion: The death rate in Rotterdam score equals is greater in our context compared to European studies.展开更多
Background: Brain malformations (BMs) are congenital abnormalities of the shape or structure of the brain, with corpus callosum agenesis known as the most frequent. Diagnosis of most BMs can be prenatal with ultrasoun...Background: Brain malformations (BMs) are congenital abnormalities of the shape or structure of the brain, with corpus callosum agenesis known as the most frequent. Diagnosis of most BMs can be prenatal with ultrasound and fetal magnetic resonance imaging (MRI);post-natal diagnosis is based on transfontanellar ultrasound, CT-scan, and head MRI which is the imaging gold standard technique. MRI has been recently introduced and the CT-scan was previously the reference technique for the diagnosis of BMs in our context. Almost no publication has been made in sub-Saharan Africa on the clinical and CT scan characteristics of Brain malformations in children. Objective: The aim of this study was, in the absence of MRI, to describe the clinical and CT-scan presentations of brain malformations in children at the Yaounde Gynaeco-Obstetric and Pediatric Hospital (YGOPH). Patients and method: This was a cross-sectional descriptive study conducted from February to May 2016 at the YGOPH, including all children of 15-year-old and less with BM diagnosed on CT-scan at YGOPH between April 2006 and March 2016. The studied variables were clinical (age at diagnosis, sex, clinical manifestations) and CT findings (type of cerebral malformation). The data was analyzed using the SPSS 20.0 software with the estimation of hospital prevalence of BMs, frequencies and associations. The chi-square test was used to seek for an association between variables. The threshold of significance was p Results: The prevalence of BMs was 0.52%, with 29 cases of BMs identified out of 5590 patients followed up at the pediatric neurology outpatient unit over a period of 10 years. The mean age at diagnosis was 37.2 months (3.1 years) and the most represented age groups were 0 - 1 year (37.9%) and 1 - 5 years (37.9%). The sex ratio was 0.81 (55.2% girls). The clinical presentation was represented by neurological signs (93.1%) with convulsions (65.5%) and psychomotor retardation (58.8%) associated with skin lesions (34.5%) and/or facial dysmorphic features (27.6%). BM was suspected on antenatal ultrasound in 14.3% of cases (4/28). Abnormalities of cortical development accounted for 65.5% of BM followed by abnormalities of brain separation (31%). Tuberous sclerosis complex was the most common BM (31%) followed by agenesis of the corpus callosum (27.6%). The presence of dysmorphic facial features was associated (p = 0.007) with disorders of brain separation (DBS) while the presence of cutaneous lesions was associated (p = 0.013) with anomalies of the cortical development (ACD) especially tuberous sclerosis complex. Conclusion: BMs are infrequent, dominated by tuberous sclerosis complex and agenesis of the corpus callosum. They are mainly revealed by convulsions and psychomotor retardation. Efforts are needed to improve antenatal diagnosis and facilitate access to cerebral MRI.展开更多
基金the Natural Science Foundation of Zhejiang Province(Grant No.LR19E090001)the Natural Science Foundation of China(Grant Nos.42077252,42011530122,and 51979272).
文摘Nonlinear flow behavior of fluids through three-dimensional(3D)discrete fracture networks(DFNs)considering effects of fracture number,surface roughness and fracture aperture was experimentally and numerically investigated.Three physical models of DFNs were 3D-printed and then computed tomography(CT)-scanned to obtain the specific geometry of fractures.The validity of numerically simulating the fluid flow through DFNs was verified via comparison with flow tests on the 3D-printed models.A parametric study was then implemented to establish quantitative relations between the coefficients/parameters in Forchheimer’s law and geometrical parameters.The results showed that the 3D-printing technique can well reproduce the geometry of single fractures with less precision when preparing complex fracture networks,numerical modeling precision of which can be improved via CT-scanning as evidenced by the well fitted results between fluid flow tests and numerical simulations using CT-scanned digital models.Streamlines in DFNs become increasingly tortuous as the fracture number and roughness increase,resulting in stronger inertial effects and greater curvatures of hydraulic pressure-low rate relations,which can be well characterized by the Forchheimer’s law.The critical hydraulic gradient for the onset of nonlinear flow decreases with the increasing aperture,fracture number and roughness,following a power function.The increases in fracture aperture and number provide more paths for fluid flow,increasing both the viscous and inertial permeabilities.The value of the inertial permeability is approximately four orders of magnitude greater than the viscous permeability,following a power function with an exponent a of 3,and a proportional coefficient b mathematically correlated with the geometrical parameters.
文摘Theaim of the present work wasto analyze moisture flow and moisture content data for high-temperature drying by usingan advanced image- processing algorithm.Since wood starts to shrink below the fibre saturation point during drying, the size and shape of wood will change. The dry wood image was thoroughly transformed to the shape of the wet wood image prior to calculating the dry weight moisture content. The use of the image- processing algorithm for the dry weight moisture content on density data from the CT-scanning during drying in a controlled high-temperature environment showed that this method is a powerful tool for analyzing the moisture flow inside the wood piece. Furthermore, the new CT-scanner together with the climate chamber gave unique results, as it has not been possible to study high-temperature drying with this method before.
文摘Brain malformations are rare, difficult to diagnose and have unpredictable evolution. They are the major causes of epilepsy, psychomotor development abnormalities and other neurological disorders. The neuroimaging technique of choice for diagnosis of these malformations is magnetic resonance imaging (MRI), but unfortunately MRI is expensive, and is not available in a poor resource country like Cameroon. CT scan associated to clinical signs can help to suspect or to confirm a malformation. The authors report here three cases of malformations discovered during cranial CT scan at the regional hospital of Ngaoundéré. They are Dandy Walker malformation, Sturge Weber’s disease and hemimegalencephaly. These cases contribute to the knowledge of this rare event, and emphasize the importance of CT scan on their diagnosis in the absence of MRI.
文摘Purpose: Despite irradiation, CT-scan remains an important diagnostic tool in epilepsy in poor countries where MRI is neither available nor affordable. But many causes of epilepsy are not accessible to CT-scan and this technique remains expensive for many poor families in countries with limited resources. The aim of this study was to determine clinical or electroencephalogram variables which could predict brain CT-scan abnormalities in childhood epilepsy. Methods: It was a cross-sectional study including 151 epileptic children who underwent head CT-scan from October 2011 to march 2012, in one university-affiliated hospital in Cameroon (YGOPH). The data collected were clinical, type of seizure, Electroencephalogram and head CT-scans results. Independent predictive factors for CT abnormalities were sought by logistic regression. A p value : Of the 151 children, 54.3% (82/151) were boys (sex ratio: 1.18 M/1F). The median age was 54 months [2 - 190 months];74.8% of children were more than 2 years old but at the onset of epilepsy they were 2 years old or less. Birth asphyxia, mental retardation and neurologic deficit were respectively associated in 62.4%, 54.3% and 51.7% of cases. Eighty-five had focal epilepsy (56.3%), 61.6% had abnormal head CT-scan, 68.9% had abnormal EEG, with no significant gender difference. The factors most significantly associated with abnormal head CT-scan were: child age ≤ 2 years, maternal hypertension/eclampsy, cerebral palsy, and child microcephaly, with 89% to 92% abnormal CT. The two independent predictors of abnormal CT were patients’ age ≤ 2 years and microcephaly. The two main CT-scan lesions were cerebral atrophy (28.5%) and brain infarct (16.6%). None of these abnormalities was correlated to any type of epilepsy. Conclusion: Almost two-thirds of head CT-scan performed in epileptic children are abnormal in our setting. Patients of 2 years old or less and those with microcephaly are very likely to have brain anomalies on CT-scan. The most common brain lesions are atrophy, cerebral infarction and porencephalic cavities. Action to reduce birth asphyxia may lead to the reduction of the incidence of epilepsy in children.
文摘Background: Detection of malignant liver mass is very important for the treatment modalities. Objective: The purpose of the present study was to establish the usefulness of CT scan in the diagnosis of malignant hepatic mass. Methodology: This cross sectional study was carried out in the Department of Radiology and Imaging at Mymensingh Medical College Hospital (MMCH), Mymensingh, Banghabandhu Sheikh Mujib Medical University (BSMMU), Dhaka and Dhaka Medical College Hospital (DMCH), Dhaka during the period of 1st January 2006 to 31st December 2007. Patients admitted in the Department of Medicine and Department of Hepatobiliary of MMCH, BSMMU, and DMCH with the clinical diagnosis of fever, abdominal pain, anorexia, nausea/vomiting, loss of appetite, jaundice, weight loss and ascites were selected as study population. CT scan and histopathology were performed to all the patients. Result: A total number of 50 patients were recruited for this study. Mean age of all patients was 51.28 ± 14 years with a range of 17 year to 78 years. Among all patients 28 had multiple lesion, of them 71.4% was malignant and 28.6% was benign. On the other side 22 patients had solitary lesion, of them 36.4% was malignant and 63.6% was benign
文摘Background: CT-scan is a very useful diagnostic tool for the detection of hepatic mass. Objective: The present study was undertaken to determine the CT-scan findings of benign and malignant hepatic mass patients. Methodology: This was a cross sectional study conducted in Radiology and Imaging Department at Mymensingh Medical College Hospital (MMCH), Mymensingh;Dhaka Medical College Hospital (DMCH), Dhaka and Banghabandhu Sheikh Mujib Medical University (BSMMU), Dhaka with the collaboration of Pathology Department of the same institute for histopathological confirmation. This study was carried out from January 2006 to December 2007 for a period of 2 years. The patients who were clinically suspected of having hepatic mass attended in the Radiology and Imaging Department in the above mentioned institutes were included as study population. All the CT-scan findings were recorded. Result: A total number of 50 patients were enrolled for this study. CT-scan was done among 40 males and 10 females with a mean age of 51.28 years old. Hypodensity was found in 17 (60.7%) and 18 (81.8%) cases in malignant and benign hepatic lesions respectively. Ill-defined margin was detected in 12 (42.9%) and 6 (27.3%) cases respectively. Calcification was present on 11 (39.3%) malignant lesion and 6 (27.3%) benign lesions. Pressure effect on biliary apparatus was found in 11 (39.3%) malignant lesions and 1 (4.5%) benign lesions (p < 0.05). Lymphadenopathy was found in 10 (35.7%) malignant lesions and 1 (4.5%) benign lesions (p < 0.05). Conclusion: In conclusion, CT-scan findings of malignant and benign hepatic mass show hypodensity with more contrast enhancement in malignant lesions with more calcification in malignant lesion;however, significant difference is detected in pressure effect on biliary apparatus and lymphadenopathy.
文摘Introduction: Cranial trauma is a serious medico-surgical pathology that hinders the vital and functional prognosis. The Rotterdam computed tomography (CT) score refined features of the Marshall score. This score was designed to categorize traumatic brain injury (TBI) type and severity in adults. The aim of our research was to evaluate the association between the Rotterdam CT scores of patients after a cranial traumatism in terms of survival. Material and methods: It was a cross-sectional and analytical study from January 2018 to March 2020, using medical records of patients suffering from cranial traumatism, received and taken in charge in the Yaounde central hospital. Results: 100 patients were retained out of 115 recruited patients. The average age was 35.20 with a sex ratio of 4.55. The Rotterdam score was between 1 and 5 with a median of 2. The overall mortality at 6 months and 1 year was 32%. With an equal score compared to European studies, we recorded significantly higher mortality. We found the sequelae in 24% of the patients. GOS ranged from 1 to 5, and survival without sequelae (GOS 1) was the most represented. There was a positive correlation between the Rotterdam score and the GOS with a Pearson correlation coefficient of +0.514. Conclusion: The death rate in Rotterdam score equals is greater in our context compared to European studies.
文摘Background: Brain malformations (BMs) are congenital abnormalities of the shape or structure of the brain, with corpus callosum agenesis known as the most frequent. Diagnosis of most BMs can be prenatal with ultrasound and fetal magnetic resonance imaging (MRI);post-natal diagnosis is based on transfontanellar ultrasound, CT-scan, and head MRI which is the imaging gold standard technique. MRI has been recently introduced and the CT-scan was previously the reference technique for the diagnosis of BMs in our context. Almost no publication has been made in sub-Saharan Africa on the clinical and CT scan characteristics of Brain malformations in children. Objective: The aim of this study was, in the absence of MRI, to describe the clinical and CT-scan presentations of brain malformations in children at the Yaounde Gynaeco-Obstetric and Pediatric Hospital (YGOPH). Patients and method: This was a cross-sectional descriptive study conducted from February to May 2016 at the YGOPH, including all children of 15-year-old and less with BM diagnosed on CT-scan at YGOPH between April 2006 and March 2016. The studied variables were clinical (age at diagnosis, sex, clinical manifestations) and CT findings (type of cerebral malformation). The data was analyzed using the SPSS 20.0 software with the estimation of hospital prevalence of BMs, frequencies and associations. The chi-square test was used to seek for an association between variables. The threshold of significance was p Results: The prevalence of BMs was 0.52%, with 29 cases of BMs identified out of 5590 patients followed up at the pediatric neurology outpatient unit over a period of 10 years. The mean age at diagnosis was 37.2 months (3.1 years) and the most represented age groups were 0 - 1 year (37.9%) and 1 - 5 years (37.9%). The sex ratio was 0.81 (55.2% girls). The clinical presentation was represented by neurological signs (93.1%) with convulsions (65.5%) and psychomotor retardation (58.8%) associated with skin lesions (34.5%) and/or facial dysmorphic features (27.6%). BM was suspected on antenatal ultrasound in 14.3% of cases (4/28). Abnormalities of cortical development accounted for 65.5% of BM followed by abnormalities of brain separation (31%). Tuberous sclerosis complex was the most common BM (31%) followed by agenesis of the corpus callosum (27.6%). The presence of dysmorphic facial features was associated (p = 0.007) with disorders of brain separation (DBS) while the presence of cutaneous lesions was associated (p = 0.013) with anomalies of the cortical development (ACD) especially tuberous sclerosis complex. Conclusion: BMs are infrequent, dominated by tuberous sclerosis complex and agenesis of the corpus callosum. They are mainly revealed by convulsions and psychomotor retardation. Efforts are needed to improve antenatal diagnosis and facilitate access to cerebral MRI.
