In cone-beam computed tomography （CBCT）, there are often cases where the size of the specimen is larger than the field of view （FOV） （referred to as over FOV-sized （OFS））. To acquire the complete projection da...In cone-beam computed tomography （CBCT）, there are often cases where the size of the specimen is larger than the field of view （FOV） （referred to as over FOV-sized （OFS））. To acquire the complete projection data for OFS objects, some scan modes have been developed for long objects and short but over-wide objects. However, these modes still cannot meet the requirements for both longitudinally long and transversely wide objects. In this paper, we propose a multiple helical scan mode and a corresponding reconstruction algorithm for both longitudinally long and transversely wide objects. The simulation results show that our model can deal with the problem and that the results are acceptable, while the OFS object is twice as long compared with the FOV in the same latitude.展开更多
Gastro-esophageal scintigraphy (milk scan) is an accurate technique for detecting gastro-esophageal reflux that can be performed rapidly with minimal patient discomfort. A retrospective study was performed to find out...Gastro-esophageal scintigraphy (milk scan) is an accurate technique for detecting gastro-esophageal reflux that can be performed rapidly with minimal patient discomfort. A retrospective study was performed to find out to how much radionuclide milk scan is sensitive for detecting gastro-esophageal reflux (GER) for 89 patients who subjected to milk scan within Years 2010 to 2013. The study group age is ranging from one month old to four years old. Milk scan was performed using PHILIPS and SEIMENS machine. Tc 99-m sulfur colloid with milk administrated orally or through nasogastric tube to the patient. The highest frequency for milk scan study was in age group of 0 - 6 months old with 77% positive finding. Patients who suffer repeated vomiting represented the highest reason of examination for milk scan (46% of overall cases), while chocking attacks, pulmonary aspiration, and congenital heart disease, were 26%, 16%, 12% respectively of the overall cases. Seventy-nine percent of patients who prepared to be examine using nasogastric tube found with positive finding, 50% of GER patients have abnormal tracer activity in the mid of esophagus;on the other hand, 50% of GER patients divided equally between the lower and upper esophagus. The study show that infants especially in age of 0 - 6 months old and with repeated vomiting symptoms are strongly recommended to milk scan study rather than fluoroscopy to avoid unnecessary dose to the patients.展开更多
Objective： The aim of our study was to explore the eikonic characteristic of skeletal metastasis of primary pul- monary carcinoma. Methods： Whole-body bone scans with 99Tcm methylene diphosphonate were performed in ...Objective： The aim of our study was to explore the eikonic characteristic of skeletal metastasis of primary pul- monary carcinoma. Methods： Whole-body bone scans with 99Tcm methylene diphosphonate were performed in 258 patients with pathologically proven pulmonary carcinoma. The rate of skeletal metastasis, distribution of the metastatic lesions and their characteristics were analyzed. Results： Among the total 258 patients, 142 cases developed skeletal metastasis. The overall rate of skeletal metastasis was 55.0%. The metastases located in axial skeleton were 49.6%, appendicular skeleton 36.0%, trunk bones of the axial skeleton 48.4%, and appendicular girdle skeleton 31.4%. Ribs, thoracic vertebrae, ilium and lumbar vertebrae had a higher rate of skeletal metastasis, which were 38.4%, 24.0%, 21.7%, 20.2%, respectively. 1252 le- sions were detected including 406 at the left side of the body, 387 lesions at the middle position and 459 at the right side of the body. There was no significant difference in terms of number of lesions between left side and right side （X2 = 3.3, P = 0.072）. 1224 skeletal metastatic foci （97.8%） were presented as strong radioactive, 26 （2.1%） as mixed lesions, and 2 （0.2%） as low radioactive. According to the shape of lesions, there were 810 punctate lesions （71.5%）, 159 （14.0%） lump form, 108 （9.5%） strip form and 56 （4.9%） lamellar form. The accumulative skeletal metastasis rate was 28.7% for the patients with one to three lesions. The metastasis rate decreased gradually as the number of metastatic lesions increased. Conclusion： Skeletal metastasis is very common in patients with pulmonary carcinoma. Most skeletal metastases are characterized by strong radio- active and earlier punctate form; they often occur in the trunk bones of axial skeleton or appendicular girdles. The distribution of earlier metastases has not obvious regularity, and advanced skeletal metastases are widely and randomly distributed in the body, which are characterized by often concurrently multiple and polymorphous lesions.展开更多
Doppler centroid frequency is an essential parameter in the imaging processing of the Scanning mode Synthetic Aperture Radar (ScanSAR). Inaccurate Doppler centroid frequency will result in ghost images in imaging resu...Doppler centroid frequency is an essential parameter in the imaging processing of the Scanning mode Synthetic Aperture Radar (ScanSAR). Inaccurate Doppler centroid frequency will result in ghost images in imaging result. In this letter, the principle and algorithms of Doppler centroid frequency estimation are introduced. Then the echo data of ScanSAR system is analyzed. Based on the algorithms of energy balancing and correlation Doppler estimator in the estimation of Doppler centroid frequency in strip mode SAR, an improved method for Doppler centroid frequency estimation in ScanSAR is proposed. The method has improved the accuracy of Doppler centroid frequency estimation in ScanSAR by zero padding between burst data. Finally, the proposed method is validated with the processing of ENVIronment SATellite Advanced Synthetic Aperture Radar (ENVISAT ASAR) wide swath raw data.展开更多
Detection of port scan is an important component in a network intrusion detection and prevention system. Traditional statistical methods can be easily evaded by stealthy scans and are prone to DoS attacks. This paper ...Detection of port scan is an important component in a network intrusion detection and prevention system. Traditional statistical methods can be easily evaded by stealthy scans and are prone to DoS attacks. This paper presents a new mechanism termed PSD(port scan detection), which is based on TCP packet anomaly evaluation. By learning the port distribution and flags of TCP packets arriving at the protected hosts, PSD can compute the anomaly score of each packet and effectively detect port scans including slow scans and stealthy scans. Experiments show that PSD has high detection accuracy and low detection latency.展开更多
Background: In view of the growing population and increased vehicle use, traumatic brain injury is becoming the most common and devastating problem especially in young healthy people. It has occupied second place next...Background: In view of the growing population and increased vehicle use, traumatic brain injury is becoming the most common and devastating problem especially in young healthy people. It has occupied second place next to cancer as leading cause of death. In this new era of radiology, computed tomography has become the primary modality of choice in the initial assessment of head injury patients as it is widely available, faster and highly accurate in detecting skull fractures and acute intracranial hemorrhage. Aim: It is to demonstrate the importance of ct scanning in the initial treatment planning, follow up and long term management of patients with acute head injury of varying severity. Patients: A retrospective study has been carried out of 100 cases of acute head trauma with positive CT scanning referred to Narayana medical college and hospital, Nellore, India between 30th April 2012 to 1st May 2013 [1 year retrospective study]. Results: The post traumatic intracranial consequences have been collected, reviewed and analyzed, where in 82% of cases males were involved , and most of the injured people belong to the first three decades of life, the main cause being road traffic accident which is growing in incidence in this 21st century. Most of the cases which were studied showed skull fractures, which indicates that there has been significant trauma and in a single case more than one pathology related to cranium has been seen. The most common post traumatic consequences found in the study of adults are contusions, brain edema and intracerebral hematomas, while other sequelae such as subarachnoid hematomas, subdural hematomas and extradural hematomas are encountered less. Diffuse and focal cerebral edema was being the most common pathology following trauma in children. Conclusion: CT scanning is the primary modality of choice in the diagnostic work up of patients with acute head trauma for identifying the various intracranial consequences following head injury especially within 48 hours which helps in the initial assessment, treatment planning, follow up and long term management of patients.展开更多
Background and Objective: Nowadays, Computer Tomography is one of the best radiological imaging technics which can give right diagnostic information, among the detection of multiphasic adenomas, the detection of cardi...Background and Objective: Nowadays, Computer Tomography is one of the best radiological imaging technics which can give right diagnostic information, among the detection of multiphasic adenomas, the detection of cardiac, cerebral and vascular abnormalities. Although these good qualities, this technic is too radiant for the patient. In this paper, we based on the irradiation doses delivered from the current protocols to find a practical method of their optimization during the pediatric cranial scan. Materials and Methods: This work relies on a collection of data from patients in the hospitals, so that analyze them, give the conclusions and, propose an optimal practical method to decrease the irradiation doses. To collect data, we performed a prospective study of seventeen months (from December 2017 to May 2019) carried out simultaneously in three hospitals of the city: The Centre Medical la Cathédrale (H1), the Yaoundé Central Hospital (H2) and the Yaoundé Gyneaco-Obstetric and pediatric hospital (H3). This study included a total of 192 cases of cerebral trauma, of which 11 cases excluded for incomplete information. The dosimetry quality control (CTDIvol) using the PMMA phantoms of 16 cm and 32 cm fulfilled. The scanographic parameters of the patient acquisition protocol were recorded and analyzed. Some of those parameters were modified and entered the CT with the help of a biomedical engineer to reduce the delivered dose. The relationship between CTDIvol and kV is statistically significant (p Results: Among patients, 172 are boys, and the remaining 9 are girls all were in the 0 to 15 age group. CTDIvol values varied from 34.2 mGy to 107.8 mGy and PDLs from 107.8 mGy.cm to 2214.5 mGy.cm in H1. In H2, CTDIvol varied from 5.8 mGy to 44 mGy and PDLs from 91.4 mGy.cm to 665.5 mGy.cm. CTDIvol varied between 9.34 mGy to 92.81 mGy and PDLs from 162.38 mGy.cm to 2713.67 mGy.cm in H3. All values are taken at 75th percentile, with or without contrast injection. Conclusion: The implementation of the optimization of protocols requires the display of the CT parameters to use and to respect during the traumatic brain tests. With displaying and respecting protocol, the CTDIvol decreased by almost 50 per cent.展开更多
The low-resolution CT scan images obtained from drill core generally struggle with problems such as insufficient pore structure information and incomplete image details.Consequently,predicting the permeability of hete...The low-resolution CT scan images obtained from drill core generally struggle with problems such as insufficient pore structure information and incomplete image details.Consequently,predicting the permeability of heterogeneous reservoir cores relies heavily on high-resolution CT scanning images.However,this approach requires a considerable amount of data and is associated with high costs.To solve this problem,a method for predicting core permeability based on deep learning using CT scan images with diff erent resolutions is proposed in this work.First,the high-resolution CT scans are preprocessed and then cubic subsets are extracted.The permeability of each subset is estimated using the Lattice Boltzmann Method(LBM)and forms the training set for the convolutional neural network(CNN)model.Subsequently,the highresolution images are downsampled to obtain the low-resolution grayscale images.In the comparative analysis of the porosities of diff erent low-resolution images,the low-resolution image with a resolution of 10%of the original image is considered as the test set in this paper.It is found that the permeabilities predicted from the low-resolution images are in good agreement with the values calculated by the LBM.In addition,the test data are compared with the results of the Kozeny-Carman(KC)model and the measured permeability of the whole sample.The results show that the prediction of the permeability of tight carbonate rock based on deep learning using CT scans with diff erent resolutions is reliable.展开更多
Stroke represents the 2<sup>nd</sup> cause of mortality and 1<sup>st</sup> cause of physical disability in the adult population. In Senegal, it represents 30% of hospitalization and 2/3 of the ...Stroke represents the 2<sup>nd</sup> cause of mortality and 1<sup>st</sup> 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. <b>Objective: </b>To specify the types of stroke and to evaluate diagnostic delays in Senegal’s regional hospitals. <b>Materials and Methods: </b>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.<b> Results: </b>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%. <b>Conclusion: </b>CT is central to the diagnosis of stroke in rural areas. However, there is a significant delay in diagnosis and management.展开更多
The singlet and triplet excited-state refraction cross-sections of dimethyl sulfoxide (DMSO) solutions of ten zinc phthalocyanine derivatives with mono-or tetra-peripheral substituents at 532 nm were obtained by simul...The singlet and triplet excited-state refraction cross-sections of dimethyl sulfoxide (DMSO) solutions of ten zinc phthalocyanine derivatives with mono-or tetra-peripheral substituents at 532 nm were obtained by simultaneous fitting of closed-aperture Z scans with both nanosecond and picosecond pulse widths. Self-focusing of both nanosecond and picosecond laser pulses was observed in all complexes at 532-nm wavelength. The complexes with tetra-substituents at the ?-position exhibit relatively larger refraction cross-sections than the other complexes. The wavelength dependence of the singlet refraction cross-section of a representative complex was observed to be non-monotonic in the range of 470 - 550 nm.展开更多
Background: Among medical technologies that use ionizing radiation, CT is currently the radio diagnostic technic that can deliver the highest radiation to the Patient compared with other conventional procedures. In de...Background: Among medical technologies that use ionizing radiation, CT is currently the radio diagnostic technic that can deliver the highest radiation to the Patient compared with other conventional procedures. In developing countries, the uses and risks of CT have not been well characterized. Objective: To estimate the lifetime attributable risk (LAR) incidence and mortality for cancer for each procedure for adult’s patients who had Computed Tomography examinations in 10 imaging centers in the city of Douala-Cameroon so as to provide a reference data. Materials and Methods: We conducted a cross-sectional study describing radiation dose associated with the 8 most common types of diagnostic CT studies performed on 1287 consecutive adult patients at 10 Douala radiology department. We estimated lifetime attributable risks of cancer by study type from these measured doses. Estimation of LAR for cancer incidence and mortality was based on the effective dose, patient’s sex and age at exposure using the BIER VII preferred models. Results: Mean effective dose from CT scans examinations varied from: 0.30 and 8.81 mSv. The highest doses were observed for lumbar spine CT (8.81 mSv), followed by abdomen-pelvis procedure (6.46 mSv), chest-abdomen-pelvic CT (6.61 mSv), chest CT (3.90 mSv), cervical Spine CT (3.05 mSv), head CT (1.7 mSv) and lower for sinus CT (0.30 mSv). The LAR values of all cancer from patients’ CT scans obtained vary from 67.13 excess per 100,000 (about 1 in 1489) and 0.45 excess per 100,000 (about 1 in 222,222). All cancer risk was high for lumbar spine CT in women 20 years old (67.13 excess deaths in 100,000 scans) followed by chest-abdomen-pelvic CT (50.36 excess deaths in 100,000 scans) and abdomen-pelvic CT (49.22 excess deaths in 100,000 scans) for the same age group. The LAR of incidence and mortality values were higher from female’s patients than males and higher for younger than older patients. Conclusion: This study was set out to estimate the LAR values associated with adult common CT scans procedures. The data indicates, LAR risks related to induced cancer from CT exposures were estimated to be low. This risk can be relatively significant for younger age group compared to older age group. The LAR values obtained will help to better evaluate radiation exposure risk, before ordering a CT scans examinations.展开更多
In order to optimize the transitional time during the successive exposure scans for a step-and-scan lithography and improve the productivity in a wafer production process, an investigation of the motion trajectory pla...In order to optimize the transitional time during the successive exposure scans for a step-and-scan lithography and improve the productivity in a wafer production process, an investigation of the motion trajectory planning along the scanning direction for wafer stage was carried out. The motions of wafer stage were divided into two respective logical moves （i. e. step-move and scan-move） and the multi-motionoverlap algorithms （MMOA） were presented for optimizing the transitional time between the successive exposure scans. The conventional motion planning method, the Hazelton method and the MMOA were analyzed theoretically and simulated using MATLAB under four different exposure field sizes. The results show that the total time between two successive scans consumed by MMOA is reduced by 4.82%, 2.62%, 3.06% and 3.96%, compared with those of the conventional motion planning method; and reduced by 2.58%, 0.76%, 1.63% and 2.92%, compared with those of the Hazehon method respectively. The theoretical analyses and simulation results illuminate that the MMOA can effectively minimize the transitional step time between successive exposure scans and therefore increase the wafer fabricating productivity.展开更多
基金Project supported by the National Basic Research Program of China (Grant No. 2011CB707701)the National High Technology Research and Development Program of China (Grant No. 2009AA012200)the National Nature Science Foundation of China(Grant No. 30970722)
文摘In cone-beam computed tomography （CBCT）, there are often cases where the size of the specimen is larger than the field of view （FOV） （referred to as over FOV-sized （OFS））. To acquire the complete projection data for OFS objects, some scan modes have been developed for long objects and short but over-wide objects. However, these modes still cannot meet the requirements for both longitudinally long and transversely wide objects. In this paper, we propose a multiple helical scan mode and a corresponding reconstruction algorithm for both longitudinally long and transversely wide objects. The simulation results show that our model can deal with the problem and that the results are acceptable, while the OFS object is twice as long compared with the FOV in the same latitude.
文摘Gastro-esophageal scintigraphy (milk scan) is an accurate technique for detecting gastro-esophageal reflux that can be performed rapidly with minimal patient discomfort. A retrospective study was performed to find out to how much radionuclide milk scan is sensitive for detecting gastro-esophageal reflux (GER) for 89 patients who subjected to milk scan within Years 2010 to 2013. The study group age is ranging from one month old to four years old. Milk scan was performed using PHILIPS and SEIMENS machine. Tc 99-m sulfur colloid with milk administrated orally or through nasogastric tube to the patient. The highest frequency for milk scan study was in age group of 0 - 6 months old with 77% positive finding. Patients who suffer repeated vomiting represented the highest reason of examination for milk scan (46% of overall cases), while chocking attacks, pulmonary aspiration, and congenital heart disease, were 26%, 16%, 12% respectively of the overall cases. Seventy-nine percent of patients who prepared to be examine using nasogastric tube found with positive finding, 50% of GER patients have abnormal tracer activity in the mid of esophagus;on the other hand, 50% of GER patients divided equally between the lower and upper esophagus. The study show that infants especially in age of 0 - 6 months old and with repeated vomiting symptoms are strongly recommended to milk scan study rather than fluoroscopy to avoid unnecessary dose to the patients.
文摘Objective： The aim of our study was to explore the eikonic characteristic of skeletal metastasis of primary pul- monary carcinoma. Methods： Whole-body bone scans with 99Tcm methylene diphosphonate were performed in 258 patients with pathologically proven pulmonary carcinoma. The rate of skeletal metastasis, distribution of the metastatic lesions and their characteristics were analyzed. Results： Among the total 258 patients, 142 cases developed skeletal metastasis. The overall rate of skeletal metastasis was 55.0%. The metastases located in axial skeleton were 49.6%, appendicular skeleton 36.0%, trunk bones of the axial skeleton 48.4%, and appendicular girdle skeleton 31.4%. Ribs, thoracic vertebrae, ilium and lumbar vertebrae had a higher rate of skeletal metastasis, which were 38.4%, 24.0%, 21.7%, 20.2%, respectively. 1252 le- sions were detected including 406 at the left side of the body, 387 lesions at the middle position and 459 at the right side of the body. There was no significant difference in terms of number of lesions between left side and right side （X2 = 3.3, P = 0.072）. 1224 skeletal metastatic foci （97.8%） were presented as strong radioactive, 26 （2.1%） as mixed lesions, and 2 （0.2%） as low radioactive. According to the shape of lesions, there were 810 punctate lesions （71.5%）, 159 （14.0%） lump form, 108 （9.5%） strip form and 56 （4.9%） lamellar form. The accumulative skeletal metastasis rate was 28.7% for the patients with one to three lesions. The metastasis rate decreased gradually as the number of metastatic lesions increased. Conclusion： Skeletal metastasis is very common in patients with pulmonary carcinoma. Most skeletal metastases are characterized by strong radio- active and earlier punctate form; they often occur in the trunk bones of axial skeleton or appendicular girdles. The distribution of earlier metastases has not obvious regularity, and advanced skeletal metastases are widely and randomly distributed in the body, which are characterized by often concurrently multiple and polymorphous lesions.
文摘Doppler centroid frequency is an essential parameter in the imaging processing of the Scanning mode Synthetic Aperture Radar (ScanSAR). Inaccurate Doppler centroid frequency will result in ghost images in imaging result. In this letter, the principle and algorithms of Doppler centroid frequency estimation are introduced. Then the echo data of ScanSAR system is analyzed. Based on the algorithms of energy balancing and correlation Doppler estimator in the estimation of Doppler centroid frequency in strip mode SAR, an improved method for Doppler centroid frequency estimation in ScanSAR is proposed. The method has improved the accuracy of Doppler centroid frequency estimation in ScanSAR by zero padding between burst data. Finally, the proposed method is validated with the processing of ENVIronment SATellite Advanced Synthetic Aperture Radar (ENVISAT ASAR) wide swath raw data.
文摘Detection of port scan is an important component in a network intrusion detection and prevention system. Traditional statistical methods can be easily evaded by stealthy scans and are prone to DoS attacks. This paper presents a new mechanism termed PSD(port scan detection), which is based on TCP packet anomaly evaluation. By learning the port distribution and flags of TCP packets arriving at the protected hosts, PSD can compute the anomaly score of each packet and effectively detect port scans including slow scans and stealthy scans. Experiments show that PSD has high detection accuracy and low detection latency.
文摘Background: In view of the growing population and increased vehicle use, traumatic brain injury is becoming the most common and devastating problem especially in young healthy people. It has occupied second place next to cancer as leading cause of death. In this new era of radiology, computed tomography has become the primary modality of choice in the initial assessment of head injury patients as it is widely available, faster and highly accurate in detecting skull fractures and acute intracranial hemorrhage. Aim: It is to demonstrate the importance of ct scanning in the initial treatment planning, follow up and long term management of patients with acute head injury of varying severity. Patients: A retrospective study has been carried out of 100 cases of acute head trauma with positive CT scanning referred to Narayana medical college and hospital, Nellore, India between 30th April 2012 to 1st May 2013 [1 year retrospective study]. Results: The post traumatic intracranial consequences have been collected, reviewed and analyzed, where in 82% of cases males were involved , and most of the injured people belong to the first three decades of life, the main cause being road traffic accident which is growing in incidence in this 21st century. Most of the cases which were studied showed skull fractures, which indicates that there has been significant trauma and in a single case more than one pathology related to cranium has been seen. The most common post traumatic consequences found in the study of adults are contusions, brain edema and intracerebral hematomas, while other sequelae such as subarachnoid hematomas, subdural hematomas and extradural hematomas are encountered less. Diffuse and focal cerebral edema was being the most common pathology following trauma in children. Conclusion: CT scanning is the primary modality of choice in the diagnostic work up of patients with acute head trauma for identifying the various intracranial consequences following head injury especially within 48 hours which helps in the initial assessment, treatment planning, follow up and long term management of patients.
文摘Background and Objective: Nowadays, Computer Tomography is one of the best radiological imaging technics which can give right diagnostic information, among the detection of multiphasic adenomas, the detection of cardiac, cerebral and vascular abnormalities. Although these good qualities, this technic is too radiant for the patient. In this paper, we based on the irradiation doses delivered from the current protocols to find a practical method of their optimization during the pediatric cranial scan. Materials and Methods: This work relies on a collection of data from patients in the hospitals, so that analyze them, give the conclusions and, propose an optimal practical method to decrease the irradiation doses. To collect data, we performed a prospective study of seventeen months (from December 2017 to May 2019) carried out simultaneously in three hospitals of the city: The Centre Medical la Cathédrale (H1), the Yaoundé Central Hospital (H2) and the Yaoundé Gyneaco-Obstetric and pediatric hospital (H3). This study included a total of 192 cases of cerebral trauma, of which 11 cases excluded for incomplete information. The dosimetry quality control (CTDIvol) using the PMMA phantoms of 16 cm and 32 cm fulfilled. The scanographic parameters of the patient acquisition protocol were recorded and analyzed. Some of those parameters were modified and entered the CT with the help of a biomedical engineer to reduce the delivered dose. The relationship between CTDIvol and kV is statistically significant (p Results: Among patients, 172 are boys, and the remaining 9 are girls all were in the 0 to 15 age group. CTDIvol values varied from 34.2 mGy to 107.8 mGy and PDLs from 107.8 mGy.cm to 2214.5 mGy.cm in H1. In H2, CTDIvol varied from 5.8 mGy to 44 mGy and PDLs from 91.4 mGy.cm to 665.5 mGy.cm. CTDIvol varied between 9.34 mGy to 92.81 mGy and PDLs from 162.38 mGy.cm to 2713.67 mGy.cm in H3. All values are taken at 75th percentile, with or without contrast injection. Conclusion: The implementation of the optimization of protocols requires the display of the CT parameters to use and to respect during the traumatic brain tests. With displaying and respecting protocol, the CTDIvol decreased by almost 50 per cent.
文摘The low-resolution CT scan images obtained from drill core generally struggle with problems such as insufficient pore structure information and incomplete image details.Consequently,predicting the permeability of heterogeneous reservoir cores relies heavily on high-resolution CT scanning images.However,this approach requires a considerable amount of data and is associated with high costs.To solve this problem,a method for predicting core permeability based on deep learning using CT scan images with diff erent resolutions is proposed in this work.First,the high-resolution CT scans are preprocessed and then cubic subsets are extracted.The permeability of each subset is estimated using the Lattice Boltzmann Method(LBM)and forms the training set for the convolutional neural network(CNN)model.Subsequently,the highresolution images are downsampled to obtain the low-resolution grayscale images.In the comparative analysis of the porosities of diff erent low-resolution images,the low-resolution image with a resolution of 10%of the original image is considered as the test set in this paper.It is found that the permeabilities predicted from the low-resolution images are in good agreement with the values calculated by the LBM.In addition,the test data are compared with the results of the Kozeny-Carman(KC)model and the measured permeability of the whole sample.The results show that the prediction of the permeability of tight carbonate rock based on deep learning using CT scans with diff erent resolutions is reliable.
文摘Stroke represents the 2<sup>nd</sup> cause of mortality and 1<sup>st</sup> 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. <b>Objective: </b>To specify the types of stroke and to evaluate diagnostic delays in Senegal’s regional hospitals. <b>Materials and Methods: </b>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.<b> Results: </b>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%. <b>Conclusion: </b>CT is central to the diagnosis of stroke in rural areas. However, there is a significant delay in diagnosis and management.
文摘The singlet and triplet excited-state refraction cross-sections of dimethyl sulfoxide (DMSO) solutions of ten zinc phthalocyanine derivatives with mono-or tetra-peripheral substituents at 532 nm were obtained by simultaneous fitting of closed-aperture Z scans with both nanosecond and picosecond pulse widths. Self-focusing of both nanosecond and picosecond laser pulses was observed in all complexes at 532-nm wavelength. The complexes with tetra-substituents at the ?-position exhibit relatively larger refraction cross-sections than the other complexes. The wavelength dependence of the singlet refraction cross-section of a representative complex was observed to be non-monotonic in the range of 470 - 550 nm.
文摘Background: Among medical technologies that use ionizing radiation, CT is currently the radio diagnostic technic that can deliver the highest radiation to the Patient compared with other conventional procedures. In developing countries, the uses and risks of CT have not been well characterized. Objective: To estimate the lifetime attributable risk (LAR) incidence and mortality for cancer for each procedure for adult’s patients who had Computed Tomography examinations in 10 imaging centers in the city of Douala-Cameroon so as to provide a reference data. Materials and Methods: We conducted a cross-sectional study describing radiation dose associated with the 8 most common types of diagnostic CT studies performed on 1287 consecutive adult patients at 10 Douala radiology department. We estimated lifetime attributable risks of cancer by study type from these measured doses. Estimation of LAR for cancer incidence and mortality was based on the effective dose, patient’s sex and age at exposure using the BIER VII preferred models. Results: Mean effective dose from CT scans examinations varied from: 0.30 and 8.81 mSv. The highest doses were observed for lumbar spine CT (8.81 mSv), followed by abdomen-pelvis procedure (6.46 mSv), chest-abdomen-pelvic CT (6.61 mSv), chest CT (3.90 mSv), cervical Spine CT (3.05 mSv), head CT (1.7 mSv) and lower for sinus CT (0.30 mSv). The LAR values of all cancer from patients’ CT scans obtained vary from 67.13 excess per 100,000 (about 1 in 1489) and 0.45 excess per 100,000 (about 1 in 222,222). All cancer risk was high for lumbar spine CT in women 20 years old (67.13 excess deaths in 100,000 scans) followed by chest-abdomen-pelvic CT (50.36 excess deaths in 100,000 scans) and abdomen-pelvic CT (49.22 excess deaths in 100,000 scans) for the same age group. The LAR of incidence and mortality values were higher from female’s patients than males and higher for younger than older patients. Conclusion: This study was set out to estimate the LAR values associated with adult common CT scans procedures. The data indicates, LAR risks related to induced cancer from CT exposures were estimated to be low. This risk can be relatively significant for younger age group compared to older age group. The LAR values obtained will help to better evaluate radiation exposure risk, before ordering a CT scans examinations.
基金the National Basic Research Program of China(No.2003CB716206)the National Natural Science Foundation of China(No.50605025)
文摘In order to optimize the transitional time during the successive exposure scans for a step-and-scan lithography and improve the productivity in a wafer production process, an investigation of the motion trajectory planning along the scanning direction for wafer stage was carried out. The motions of wafer stage were divided into two respective logical moves （i. e. step-move and scan-move） and the multi-motionoverlap algorithms （MMOA） were presented for optimizing the transitional time between the successive exposure scans. The conventional motion planning method, the Hazelton method and the MMOA were analyzed theoretically and simulated using MATLAB under four different exposure field sizes. The results show that the total time between two successive scans consumed by MMOA is reduced by 4.82%, 2.62%, 3.06% and 3.96%, compared with those of the conventional motion planning method; and reduced by 2.58%, 0.76%, 1.63% and 2.92%, compared with those of the Hazehon method respectively. The theoretical analyses and simulation results illuminate that the MMOA can effectively minimize the transitional step time between successive exposure scans and therefore increase the wafer fabricating productivity.
