Introduction: Computed tomography (CT) measurements of bone mineral attenuation may be a useful means to identify older women who should be prioritized for bone mineral density screening. Methods: We compared bone min...Introduction: Computed tomography (CT) measurements of bone mineral attenuation may be a useful means to identify older women who should be prioritized for bone mineral density screening. Methods: We compared bone mineral attenuation as measured in the L1 vertebra of CT studies to the results of dual-energy x-ray absorptiometry (DEXA) studies to determine what CT attenuation thresholds might yield a reasonable combination of sensitivity and specificity for the detection of osteoporosis. The study was limited to women between the ages of 65 and 75 years who had a DEXA study and a CT that included the L1 or adjacent vertebra performed within 3 years of the DEXA study. Results: There were 1226 women in this study, of whom 452 (38%) had osteoporosis based on a T-score ≤ −2.5 by DEXA. There were 830 CT studies performed with contrast and 396 studies which were performed without contrast. There was a statistically significant difference in the mean HU of those studies performed without contrast compared to those with contrast (unenhanced mean 103 HU versus 125 HU, p < 0.001). Different CT attenuation thresholds provided the most appropriate combination of sensitivity and specificity for the detection of osteoporosis when comparing CT studies performed without or with IV contrast and when all the CT data were used in aggregate. Conclusion: Different thresholds appear necessary when using the mean CT vertebral attenuation to identify older women for preferential referral for DEXA studies.展开更多
A comprehensive study was presented for WLAN 802.11b using error-prone channel. It was theoretically and numerically evaluated the performance of three different network sizes with the bit rates that available in 802....A comprehensive study was presented for WLAN 802.11b using error-prone channel. It was theoretically and numerically evaluated the performance of three different network sizes with the bit rates that available in 802.11b protocol. Results show that throughput does not change with the size of the network for wide range of bit error rates (BERs) and the channel bit rates play a significant role in the main characteristics of the network. A comprehensive explanation has given for the phenomenon of the packet delay suppression at relatively high level of BERs in view of the size of the networks and the BERs. The effect length of the transmitting packets is also investigated.展开更多
Based on delicate mathematical model, the average time in a successful and unsuccessful transmission is worked out. Then the relation between network saturation throughput and RTS threshold is found and expressed in a...Based on delicate mathematical model, the average time in a successful and unsuccessful transmission is worked out. Then the relation between network saturation throughput and RTS threshold is found and expressed in a theoretical formula. Our analysis shows that there is an optimum RTS threshold that can maximize the network capacity. The numerical techniques to find out the optimum RTS threshold are also presented. All these analysis are well validated by computer simulation.展开更多
Altered igneous reservoirs have low porosity and permeability,compact structure and certain heterogeneity.A simple digital core with certain generality and multi-parameter constraints can be con-structed to characteri...Altered igneous reservoirs have low porosity and permeability,compact structure and certain heterogeneity.A simple digital core with certain generality and multi-parameter constraints can be con-structed to characterize the microscopic pore structure and mineral composition.In this paper,based on core X-ray,CT images and whole-rock mineral analysis,threshold segmentation of mass content and grayscale distribution of various minerals in different lithologies of igneous rocks in the buried hill of Huizhou depression is carried out to construct digital core of altered igneous rocks.The results show that after converting the mineral mass content into volume content,the minerals of altered igneous rocks in Huizhou depression can be classified into components.According to the range of grayscale value,components can be divided into six parts.Due to the difference of the content of components in different lithologies of igneous rocks,differentiated grayscale threshold segmentation is needed to obtain the digital core for a single lithology.The final digital core generation process includes two steps:building a single component digital core,and stacking and combining.This kind of universal digital core model can support the subsequent pore scale numerical simulation and comprehensive rock physics research.展开更多
Knee Osteoarthritis(OA)is a joint disease that is commonly observed in people around the world.Osteoarthritis commonly affects patients who are obese and those above the age of 60.A valid knee image was generated by C...Knee Osteoarthritis(OA)is a joint disease that is commonly observed in people around the world.Osteoarthritis commonly affects patients who are obese and those above the age of 60.A valid knee image was generated by Computed Tomography(CT).In this work,efficient segmentation of CT images using Elephant Herding Optimization(EHO)optimization is implemented.The initial stage employs,the CT image normalization and the normalized image is incited to image enhancement through histogram correlation.Consequently,the enhanced image is segmented by utilizing Niblack and Bernsen algorithm.The(EHO)optimized outcome is evaluated in two steps.The initial step includes image enhancement with the measure of Mean square error(MSE),Peak signal to noise ratio(PSNR)and Structural similarity index(SSIM).The following step includes the segmentation which includes the measure ofAccuracy,Sensitivity and Specificity.The comparative analysis of EHO provides 95%of accuracy,94%of specificity and 93%of sensitivity than that of Active contour and Otsu threshold.展开更多
文摘Introduction: Computed tomography (CT) measurements of bone mineral attenuation may be a useful means to identify older women who should be prioritized for bone mineral density screening. Methods: We compared bone mineral attenuation as measured in the L1 vertebra of CT studies to the results of dual-energy x-ray absorptiometry (DEXA) studies to determine what CT attenuation thresholds might yield a reasonable combination of sensitivity and specificity for the detection of osteoporosis. The study was limited to women between the ages of 65 and 75 years who had a DEXA study and a CT that included the L1 or adjacent vertebra performed within 3 years of the DEXA study. Results: There were 1226 women in this study, of whom 452 (38%) had osteoporosis based on a T-score ≤ −2.5 by DEXA. There were 830 CT studies performed with contrast and 396 studies which were performed without contrast. There was a statistically significant difference in the mean HU of those studies performed without contrast compared to those with contrast (unenhanced mean 103 HU versus 125 HU, p < 0.001). Different CT attenuation thresholds provided the most appropriate combination of sensitivity and specificity for the detection of osteoporosis when comparing CT studies performed without or with IV contrast and when all the CT data were used in aggregate. Conclusion: Different thresholds appear necessary when using the mean CT vertebral attenuation to identify older women for preferential referral for DEXA studies.
文摘A comprehensive study was presented for WLAN 802.11b using error-prone channel. It was theoretically and numerically evaluated the performance of three different network sizes with the bit rates that available in 802.11b protocol. Results show that throughput does not change with the size of the network for wide range of bit error rates (BERs) and the channel bit rates play a significant role in the main characteristics of the network. A comprehensive explanation has given for the phenomenon of the packet delay suppression at relatively high level of BERs in view of the size of the networks and the BERs. The effect length of the transmitting packets is also investigated.
基金Supported by the Foundation of National 863 Programme of China (No.2001AA120303 )
文摘Based on delicate mathematical model, the average time in a successful and unsuccessful transmission is worked out. Then the relation between network saturation throughput and RTS threshold is found and expressed in a theoretical formula. Our analysis shows that there is an optimum RTS threshold that can maximize the network capacity. The numerical techniques to find out the optimum RTS threshold are also presented. All these analysis are well validated by computer simulation.
基金Supported by Project of the National Natural Science Foundation of China (No. 42072323)
文摘Altered igneous reservoirs have low porosity and permeability,compact structure and certain heterogeneity.A simple digital core with certain generality and multi-parameter constraints can be con-structed to characterize the microscopic pore structure and mineral composition.In this paper,based on core X-ray,CT images and whole-rock mineral analysis,threshold segmentation of mass content and grayscale distribution of various minerals in different lithologies of igneous rocks in the buried hill of Huizhou depression is carried out to construct digital core of altered igneous rocks.The results show that after converting the mineral mass content into volume content,the minerals of altered igneous rocks in Huizhou depression can be classified into components.According to the range of grayscale value,components can be divided into six parts.Due to the difference of the content of components in different lithologies of igneous rocks,differentiated grayscale threshold segmentation is needed to obtain the digital core for a single lithology.The final digital core generation process includes two steps:building a single component digital core,and stacking and combining.This kind of universal digital core model can support the subsequent pore scale numerical simulation and comprehensive rock physics research.
基金This research work was fully supported by King Khalid University,Abha,Kingdom of Saudi Arabia,for funding this work through a General Research Project under grant number RGP/119/42.
文摘Knee Osteoarthritis(OA)is a joint disease that is commonly observed in people around the world.Osteoarthritis commonly affects patients who are obese and those above the age of 60.A valid knee image was generated by Computed Tomography(CT).In this work,efficient segmentation of CT images using Elephant Herding Optimization(EHO)optimization is implemented.The initial stage employs,the CT image normalization and the normalized image is incited to image enhancement through histogram correlation.Consequently,the enhanced image is segmented by utilizing Niblack and Bernsen algorithm.The(EHO)optimized outcome is evaluated in two steps.The initial step includes image enhancement with the measure of Mean square error(MSE),Peak signal to noise ratio(PSNR)and Structural similarity index(SSIM).The following step includes the segmentation which includes the measure ofAccuracy,Sensitivity and Specificity.The comparative analysis of EHO provides 95%of accuracy,94%of specificity and 93%of sensitivity than that of Active contour and Otsu threshold.
