High-definition(HD)maps are key components that provide rich topologic and semantic information for decision-making in vehicle autonomous driving systems.A complete ground orthophoto is usually used as the base image ...High-definition(HD)maps are key components that provide rich topologic and semantic information for decision-making in vehicle autonomous driving systems.A complete ground orthophoto is usually used as the base image to construct the HD map.The ground orthophoto is obtained through inverse perspective transformation and image mosaicing.During the image mosaicing,multiple consecutive orthophotos are stitched together using pose information and image registration.In this study,wavelet transform is introduced to the image mosaicing process to alleviate the information loss caused by image overlapping.In the orthophoto wavelet transform,high-frequency and low-frequency components are fused using different strategies to form a complete base image with clearer local details.Experimental results show that the accuracy of the orthophotos generated using this method is improved.展开更多
With the growth in the vehicle industry,autonomous driving has become a hot topic worldwide and has attracted increasing attention from both industrial and academic sectors.Maps,as pivotal geospatial information carri...With the growth in the vehicle industry,autonomous driving has become a hot topic worldwide and has attracted increasing attention from both industrial and academic sectors.Maps,as pivotal geospatial information carriers,play a vital role in route planning and navigation service.Compared with conventional maps,high-definition(HD)maps possesses higher precision,richer information,and various services and are regarded as critical infrastructure for autonomous driving.However,heterogeneous HD map data standards and models have different characteristics and advantages,and thus they rarely meet all autonomous driving requirements for different driving objectives.This research presents an interoperable map data model,the Open HD Map Service Model(OHDMSM),to provide a reference for HD map development.The designed OHDMSM,which contains three data layers and a set of corresponding interfaces,demonstrates high interoperability for HD map data fusion and application.As a proof of concept,an HD map data system is implemented with all functions following the designed data model and interfaces of OHDMSM.The design and development of OHDMSM data structures,interfaces and systems will benefit data requesting,updating,and interoperation for HD map data worldwide,which can be helpful for developing autonomous driving and intelligent transportation in the Digital Earth.展开更多
Unmanned aerial vehicles(UAVs)bring more innovation and attraction to outdoor mobile high-definition(HD)live streaming with its unique perspective.Due to the heavy computational requirements of HD live broadcast tasks...Unmanned aerial vehicles(UAVs)bring more innovation and attraction to outdoor mobile high-definition(HD)live streaming with its unique perspective.Due to the heavy computational requirements of HD live broadcast tasks and the limited hardware performance of UAV equipment,how to reduce the system response delay and improve the energy efficiency of terminal equipment directly affects the secure broadcast of the system.Secure task offloading in this scenario is considered a promising solution and has received academic attention.In this paper,we simulate the UAV-aided outdoor mobile HD live streaming scenarios and optimize the relevant task offloading strategies.First,we design the total cost function of task offloading that jointly optimizes secure time latency and energy consumption.Additionally,we propose a collaborative computing model for multi-UAV task offloading.This model combines the idea of simulated annealing(SA)and introduces the compression factor to enhance the particle swarm optimization(PSO)to realize secure task offloading.The simulation results show that the proposed strategy has better performance in balancing network latency and energy consumption.Compared with the discrete teaching–learning-based optimization(DTLBO)and quantum PSO(QPSO)task offloading strategies,the fitness value of the proposed strategy is decreased by an average of 26.73%and 16.42%,respectively.展开更多
Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening pa...Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening particles also deteriorates the processability and it is of great importance to establish accurate processing maps to guide the thermomechanical processes to enhance the formability.In this study,we performed particle swarm optimization-based back propagation artificial neural network model to predict the high temperature flow behavior of 0.25wt%Al2O3 particle-reinforced Cu alloys,and compared the accuracy with that of derived by Arrhenius-type constitutive model and back propagation artificial neural network model.To train these models,we obtained the raw data by fabricating ODS Cu alloys using the internal oxidation and reduction method,and conducting systematic hot compression tests between 400 and800℃with strain rates of 10^(-2)-10 S^(-1).At last,processing maps for ODS Cu alloys were proposed by combining processing parameters,mechanical behavior,microstructure characterization,and the modeling results achieved a coefficient of determination higher than>99%.展开更多
AIM： To investigate if high-definition （HD） colonoscope with i-Scan gave a higher detection rate of mucosal le- sions vs standard white-light instruments. METHODS： Data were collected from the computer- ized datab...AIM： To investigate if high-definition （HD） colonoscope with i-Scan gave a higher detection rate of mucosal le- sions vs standard white-light instruments. METHODS： Data were collected from the computer- ized database of the endoscopy unit of our tertiary referral center. We retrospectively analyzed 1101 con- secutive colonoscopies that were performed over 1 year with standard white-light （n = 849） or HD＋ with i-Scan （n = 252） instruments by four endoscopists, in an outpatient setting. Colonoscopy records included patients＇ main details and family history for colorectal cancer, indication for colonoscopy （screening, diagnos- tic or surveillance）, type of instrument used （standard white-light or HD＋ plus i-Scan）, name of endoscopist and bowel preparation. Records for each procedure included whether the cecum was reached or not and the reason for failure, complications during or imme- diately after the procedure, and number, size, location and characteristics of the lesions. Polyps or protruding lesions were defined as sessile or pedunculated, and nonprotruding lesions were defined according to Paris classification. For each lesion, histological diagnosis was recorded. RESULTS： Eight hundred and forty-nine colonosco- pies were carried with the standard white-light video colonoscope and 252 with the HD＋ plus i-Scan video colonoscope, The four endoscopists did 264, 300, 276 and 261 procedures, respectively; 21.6%, 24.0%, 21.7% and 24.1% of them with the HD＋ plus i-Scan technique. There were no significant differences be- tween the four endoscopists in either the number of procedures done or the proportions of each imaging technique used. Both techniques detected one or more mucosal lesions in 522/1101 procedures （47.4%）. The overall number of lesions recognized was 1266; 645 in the right colon and 621 in the left. A significantly higher number of colonoscopies recognized lesions in the HD＋ plus i-Scan mode （171/252 = 67.9%） than with the standard white-light technique （408/849 = 48.1%） （P 〈 0.0001）. HD＋ with i-Scan colonoscopies identified more lesions than standard white-light imag- ing （459/252 and 807/849, P 〈 0.0001）, in the right or left colon （mean ：1： SD, 1.62±1.36 vs 1.33±0.73, P 〈 0.003 and 1.55±0.98 vs 1.17±0.93, P = 0.033）, more lesions 〈 10 mm （P 〈 0.0001） or nonprotruding （P 〈 0.022）, and flat polyps （P = 0.04）. The cumulative mean number of lesions per procedure detected by the four endoscopists was significantly higher with HD＋ with i-Scan than with standard white-light imaging （1.82 ± 2.89 vs 0.95± 1.35, P 〈 0.0001）. CONCLUSION： HD imaging with i-Scan during the withdrawal phase of colonoscopy significantly increased the detection of colonic mucosal lesions, particularly small and nonprotruding polyps.展开更多
Objective This study aimed to compare the performance of standard-definition white-light endoscopy(SD-WL),high-definition white-light endoscopy(HD-WL),and high-definition narrow-band imaging(HD-NBI)in detecting colore...Objective This study aimed to compare the performance of standard-definition white-light endoscopy(SD-WL),high-definition white-light endoscopy(HD-WL),and high-definition narrow-band imaging(HD-NBI)in detecting colorectal lesions in the Chinese population.Methods This was a multicenter,single-blind,randomized,controlled trial with a non-inferiority design.Patients undergoing endoscopy for physical examination,screening,and surveillance were enrolled from July 2017 to December 2020.The primary outcome measure was the adenoma detection rate(ADR),defined as the proportion of patients with at least one adenoma detected.The associated factors for detecting adenomas were assessed using univariate and multivariate logistic regression.Results Out of 653 eligible patients enrolled,data from 596 patients were analyzed.The ADRs were 34.5%in the SD-WL group,33.5%in the HD-WL group,and 37.5%in the HD-NBI group(P=0.72).The advanced neoplasm detection rates(ANDRs)in the three arms were 17.1%,15.5%,and 10.4%(P=0.17).No significant differences were found between the SD group and HD group regarding ADR or ANDR(ADR:34.5%vs.35.6%,P=0.79;ANDR:17.1%vs.13.0%,P=0.16,respectively).Similar results were observed between the HD-WL group and HD-NBI group(ADR:33.5%vs.37.7%,P=0.45;ANDR:15.5%vs.10.4%,P=0.18,respectively).In the univariate and multivariate logistic regression analyses,neither HD-WL nor HD-NBI led to a significant difference in overall adenoma detection compared to SD-WL(HD-WL:OR 0.91,P=0.69;HD-NBI:OR 1.15,P=0.80).Conclusion HD-NBI and HD-WL are comparable to SD-WL for overall adenoma detection among Chinese outpatients.It can be concluded that HD-NBI or HD-WL is not superior to SD-WL,but more effective instruction may be needed to guide the selection of different endoscopic methods in the future.Our study’s conclusions may aid in the efficient allocation and utilization of limited colonoscopy resources,especially advanced imaging technologies.展开更多
AIM:To examine performances regarding prediction of polyp histology using high-definition (HD) i-scan in a group of endoscopists with varying levels of experience. METHODS:We used a digital library of HD i-scan still ...AIM:To examine performances regarding prediction of polyp histology using high-definition (HD) i-scan in a group of endoscopists with varying levels of experience. METHODS:We used a digital library of HD i-scan still images, comprising twin pictures (surface enhancement and tone enhancement), collected at our university hospital. We defined endoscopic features of adenomatous and non-adenomatous polyps, according to the following parameters:color, surface pattern and vascular pattern. We familiarized the participating endoscopists on optical diagnosis of colorectal polyps using a 20-min didactic training session. All endoscopists were asked to evaluate an image set of 50 colorectal polyps with regard to polyp histology. We classified the diagnoses into high confidence (i.e., cases in which the endoscopist could assign a diagnosis with certainty) and low confidence diagnoses (i.e., cases in which the endoscopist preferred to send the polyp for formal histology). Mean sensitivity, specificity and accuracy per endoscopist/image were computed and differences between groups tested using independent-samples t tests. High vs low confidence diagnoses were compared using the pairedsamples t test. RESULTS:Eleven endoscopists without previous experience on optical diagnosis evaluated a total of 550 images (396 adenomatous, 154 non-adenomatous). Mean sensitivity, specificity and accuracy for diagnosing adenomas were 79.3%, 85.7% and 81.1%, respectively. No significant differences were found between gastroenterologists and trainees regarding performances of optical diagnosis (mean accuracy 78.0%vs 82.9%,P = 0.098). Diminutive lesions were predicted with a lower mean accuracy as compared to non-diminutive lesions (74.2% vs 93.1%, P = 0.008). A total of 446 (81.1%) diagnoses were made with high confidence. High confidence diagnoses corresponded to a significantly higher mean accuracy than low confidence diagnoses (84.0% vs 64.3%, P = 0.008). A total of 319 (58.0%) images were evaluated as having excellent quality. Considering excellent quality images in conjunction with high confidence diagnosis, overall accuracy increased to 92.8%. CONCLUSION:After a single training session, endoscopists with varying levels of experience can already provide optical diagnosis with an accuracy of 84.0%.展开更多
目的基于T2^(*)mapping定量分析业余马拉松运动员足踝部关节软骨的T2^(*)值,并分析其与性别、年龄、身体质量指数(body mass index,BMI)、跑龄、跑量之间的相关性。材料与方法于2023年7月份至2023年9月份招募重庆市长跑运动爱好者48名,...目的基于T2^(*)mapping定量分析业余马拉松运动员足踝部关节软骨的T2^(*)值,并分析其与性别、年龄、身体质量指数(body mass index,BMI)、跑龄、跑量之间的相关性。材料与方法于2023年7月份至2023年9月份招募重庆市长跑运动爱好者48名,其中跑量<300 km/月的36例(中低跑量组),跑量≥300 km/月的12例(高跑量组)。所有受试者均进行单侧无症状踝关节的MRI扫描,扫描序列包括T2^(*)mapping多回波自旋回波(spin echo,SE)序列矢状位、质子密度加权成像脂肪抑制(proton density-weighted imaging fat-saturated,PDWI-FS)序列矢状位、冠状位、横轴位以及T1加权脂肪抑制成像(T1-weighted imaging fat-saturated,T1WI-FS)序列横轴位。沿关节软骨轮廓边缘勾画距骨穹窿、跟骰关节跟骨面、骰骨面及后距下关节跟骨面、距骨面软骨作为感兴趣区(region of interest,ROI),获得相应的T2^(*)值。采用线性回归分析软骨T2^(*)值与年龄、BMI、跑龄的相关性,采用独立样本t检验分析不同跑量及不同性别间的软骨T2^(*)值差异。结果(1)距骨穹窿、跟骰关节跟骨面及骰骨面、后距下关节跟骨面及距骨面软骨T2^(*)值在性别上的差异均具有统计学意义(P=0.001、P<0.001、P=0.002、P=0.008、P=0.004);(2)高跑量组的距骨穹窿、后距下关节跟骨面软骨T2^(*)值高于中低跑量组(P=0.014、0.023),不同跑量的跟骰关节跟骨面及骰骨面、后距下关节距骨面软骨T2^(*)值的差异均无统计学意义(P=0.987、0.072、0.724);(3)距骨穹窿、跟骰关节跟骨面及骰骨面、后距下关节跟骨面、距骨面软骨T2^(*)值均与BMI呈正相关(r=0.376、0.384、0.300、0.422、0.455,P=0.005、0.004、0.019、0.001、0.001)。结论在业余马拉松运动员这一跑步群体中,与中低跑量相比,高跑量更有可能导致距骨穹窿、后距下关节跟骨面软骨损伤;而与较低的BMI相比,高BMI增加了距骨穹窿、跟骰关节跟骨面、骰骨面及后距下关节跟骨面、距骨面软骨损伤的风险。展开更多
There is an increasing demand for supporting high-quality real-time audiovisual services for the next generation wired and wireless networks. However, due to variety of bandwidths of different networks, it is a great ...There is an increasing demand for supporting high-quality real-time audiovisual services for the next generation wired and wireless networks. However, due to variety of bandwidths of different networks, it is a great challenge for deployment. In this paper, a novel high-definition (HD) video transmission system was proposed which depends upon reliable compound multicast protocols and QoS control over the various kinds of networks. This system detects client's network condition and assigns it to a proper proxy. Each proxy is capable of detecting network parameters and adaptively tuning such transport parameters as bit rate, video resolution, frame rate and QoS mechanisms to this condition. It also provides FEC error recovery under consideration of characteristics of MPEG4 video codec. Our simulation demonstrates that different network clients such as ADSL, CERNET, and CERNET2 can receive more video reliability with less delay.展开更多
基金the National Natural Science Foundation of China(No.U1764264/61873165)the Shanghai Automotive Industry Science and Technology Development Foundation(No.1807)the Guangxi Key Laboratory of Automobile Components and Vehicle Technology Research Project(No.2020GKLACVTKF02)。
文摘High-definition(HD)maps are key components that provide rich topologic and semantic information for decision-making in vehicle autonomous driving systems.A complete ground orthophoto is usually used as the base image to construct the HD map.The ground orthophoto is obtained through inverse perspective transformation and image mosaicing.During the image mosaicing,multiple consecutive orthophotos are stitched together using pose information and image registration.In this study,wavelet transform is introduced to the image mosaicing process to alleviate the information loss caused by image overlapping.In the orthophoto wavelet transform,high-frequency and low-frequency components are fused using different strategies to form a complete base image with clearer local details.Experimental results show that the accuracy of the orthophotos generated using this method is improved.
基金supported by National Key Research and Development Program of China:[Grant Number 2021YFB2501101]Smart Cities Research Institute(Q-CDA7)at the Hong Kong Polytechnic University:[Grant Number Q-CDA7]Guangdong Science and Technology Strategic Innovation Fund(the Guangdong–Hong Kong-Macao Joint Laboratory Program):Guangdong Science and Technology Strategic Innovation Fund:[Grant Number 2020B12120300092020B1212030009].
文摘With the growth in the vehicle industry,autonomous driving has become a hot topic worldwide and has attracted increasing attention from both industrial and academic sectors.Maps,as pivotal geospatial information carriers,play a vital role in route planning and navigation service.Compared with conventional maps,high-definition(HD)maps possesses higher precision,richer information,and various services and are regarded as critical infrastructure for autonomous driving.However,heterogeneous HD map data standards and models have different characteristics and advantages,and thus they rarely meet all autonomous driving requirements for different driving objectives.This research presents an interoperable map data model,the Open HD Map Service Model(OHDMSM),to provide a reference for HD map development.The designed OHDMSM,which contains three data layers and a set of corresponding interfaces,demonstrates high interoperability for HD map data fusion and application.As a proof of concept,an HD map data system is implemented with all functions following the designed data model and interfaces of OHDMSM.The design and development of OHDMSM data structures,interfaces and systems will benefit data requesting,updating,and interoperation for HD map data worldwide,which can be helpful for developing autonomous driving and intelligent transportation in the Digital Earth.
基金supported in part by the National Natural Science Foundation of China(Nos.62271454 and 62171119).
文摘Unmanned aerial vehicles(UAVs)bring more innovation and attraction to outdoor mobile high-definition(HD)live streaming with its unique perspective.Due to the heavy computational requirements of HD live broadcast tasks and the limited hardware performance of UAV equipment,how to reduce the system response delay and improve the energy efficiency of terminal equipment directly affects the secure broadcast of the system.Secure task offloading in this scenario is considered a promising solution and has received academic attention.In this paper,we simulate the UAV-aided outdoor mobile HD live streaming scenarios and optimize the relevant task offloading strategies.First,we design the total cost function of task offloading that jointly optimizes secure time latency and energy consumption.Additionally,we propose a collaborative computing model for multi-UAV task offloading.This model combines the idea of simulated annealing(SA)and introduces the compression factor to enhance the particle swarm optimization(PSO)to realize secure task offloading.The simulation results show that the proposed strategy has better performance in balancing network latency and energy consumption.Compared with the discrete teaching–learning-based optimization(DTLBO)and quantum PSO(QPSO)task offloading strategies,the fitness value of the proposed strategy is decreased by an average of 26.73%and 16.42%,respectively.
基金financial support of the National Natural Science Foundation of China(No.52371103)the Fundamental Research Funds for the Central Universities,China(No.2242023K40028)+1 种基金the Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials,China(No.AMM2023B01).financial support of the Research Fund of Shihezi Key Laboratory of AluminumBased Advanced Materials,China(No.2023PT02)financial support of Guangdong Province Science and Technology Major Project,China(No.2021B0301030005)。
文摘Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening particles also deteriorates the processability and it is of great importance to establish accurate processing maps to guide the thermomechanical processes to enhance the formability.In this study,we performed particle swarm optimization-based back propagation artificial neural network model to predict the high temperature flow behavior of 0.25wt%Al2O3 particle-reinforced Cu alloys,and compared the accuracy with that of derived by Arrhenius-type constitutive model and back propagation artificial neural network model.To train these models,we obtained the raw data by fabricating ODS Cu alloys using the internal oxidation and reduction method,and conducting systematic hot compression tests between 400 and800℃with strain rates of 10^(-2)-10 S^(-1).At last,processing maps for ODS Cu alloys were proposed by combining processing parameters,mechanical behavior,microstructure characterization,and the modeling results achieved a coefficient of determination higher than>99%.
文摘AIM： To investigate if high-definition （HD） colonoscope with i-Scan gave a higher detection rate of mucosal le- sions vs standard white-light instruments. METHODS： Data were collected from the computer- ized database of the endoscopy unit of our tertiary referral center. We retrospectively analyzed 1101 con- secutive colonoscopies that were performed over 1 year with standard white-light （n = 849） or HD＋ with i-Scan （n = 252） instruments by four endoscopists, in an outpatient setting. Colonoscopy records included patients＇ main details and family history for colorectal cancer, indication for colonoscopy （screening, diagnos- tic or surveillance）, type of instrument used （standard white-light or HD＋ plus i-Scan）, name of endoscopist and bowel preparation. Records for each procedure included whether the cecum was reached or not and the reason for failure, complications during or imme- diately after the procedure, and number, size, location and characteristics of the lesions. Polyps or protruding lesions were defined as sessile or pedunculated, and nonprotruding lesions were defined according to Paris classification. For each lesion, histological diagnosis was recorded. RESULTS： Eight hundred and forty-nine colonosco- pies were carried with the standard white-light video colonoscope and 252 with the HD＋ plus i-Scan video colonoscope, The four endoscopists did 264, 300, 276 and 261 procedures, respectively; 21.6%, 24.0%, 21.7% and 24.1% of them with the HD＋ plus i-Scan technique. There were no significant differences be- tween the four endoscopists in either the number of procedures done or the proportions of each imaging technique used. Both techniques detected one or more mucosal lesions in 522/1101 procedures （47.4%）. The overall number of lesions recognized was 1266; 645 in the right colon and 621 in the left. A significantly higher number of colonoscopies recognized lesions in the HD＋ plus i-Scan mode （171/252 = 67.9%） than with the standard white-light technique （408/849 = 48.1%） （P 〈 0.0001）. HD＋ with i-Scan colonoscopies identified more lesions than standard white-light imag- ing （459/252 and 807/849, P 〈 0.0001）, in the right or left colon （mean ：1： SD, 1.62±1.36 vs 1.33±0.73, P 〈 0.003 and 1.55±0.98 vs 1.17±0.93, P = 0.033）, more lesions 〈 10 mm （P 〈 0.0001） or nonprotruding （P 〈 0.022）, and flat polyps （P = 0.04）. The cumulative mean number of lesions per procedure detected by the four endoscopists was significantly higher with HD＋ with i-Scan than with standard white-light imaging （1.82 ± 2.89 vs 0.95± 1.35, P 〈 0.0001）. CONCLUSION： HD imaging with i-Scan during the withdrawal phase of colonoscopy significantly increased the detection of colonic mucosal lesions, particularly small and nonprotruding polyps.
基金supported by the Beijing Municipal Science and Technology Commission(BMSTC,No.D171100002617001).
文摘Objective This study aimed to compare the performance of standard-definition white-light endoscopy(SD-WL),high-definition white-light endoscopy(HD-WL),and high-definition narrow-band imaging(HD-NBI)in detecting colorectal lesions in the Chinese population.Methods This was a multicenter,single-blind,randomized,controlled trial with a non-inferiority design.Patients undergoing endoscopy for physical examination,screening,and surveillance were enrolled from July 2017 to December 2020.The primary outcome measure was the adenoma detection rate(ADR),defined as the proportion of patients with at least one adenoma detected.The associated factors for detecting adenomas were assessed using univariate and multivariate logistic regression.Results Out of 653 eligible patients enrolled,data from 596 patients were analyzed.The ADRs were 34.5%in the SD-WL group,33.5%in the HD-WL group,and 37.5%in the HD-NBI group(P=0.72).The advanced neoplasm detection rates(ANDRs)in the three arms were 17.1%,15.5%,and 10.4%(P=0.17).No significant differences were found between the SD group and HD group regarding ADR or ANDR(ADR:34.5%vs.35.6%,P=0.79;ANDR:17.1%vs.13.0%,P=0.16,respectively).Similar results were observed between the HD-WL group and HD-NBI group(ADR:33.5%vs.37.7%,P=0.45;ANDR:15.5%vs.10.4%,P=0.18,respectively).In the univariate and multivariate logistic regression analyses,neither HD-WL nor HD-NBI led to a significant difference in overall adenoma detection compared to SD-WL(HD-WL:OR 0.91,P=0.69;HD-NBI:OR 1.15,P=0.80).Conclusion HD-NBI and HD-WL are comparable to SD-WL for overall adenoma detection among Chinese outpatients.It can be concluded that HD-NBI or HD-WL is not superior to SD-WL,but more effective instruction may be needed to guide the selection of different endoscopic methods in the future.Our study’s conclusions may aid in the efficient allocation and utilization of limited colonoscopy resources,especially advanced imaging technologies.
文摘AIM:To examine performances regarding prediction of polyp histology using high-definition (HD) i-scan in a group of endoscopists with varying levels of experience. METHODS:We used a digital library of HD i-scan still images, comprising twin pictures (surface enhancement and tone enhancement), collected at our university hospital. We defined endoscopic features of adenomatous and non-adenomatous polyps, according to the following parameters:color, surface pattern and vascular pattern. We familiarized the participating endoscopists on optical diagnosis of colorectal polyps using a 20-min didactic training session. All endoscopists were asked to evaluate an image set of 50 colorectal polyps with regard to polyp histology. We classified the diagnoses into high confidence (i.e., cases in which the endoscopist could assign a diagnosis with certainty) and low confidence diagnoses (i.e., cases in which the endoscopist preferred to send the polyp for formal histology). Mean sensitivity, specificity and accuracy per endoscopist/image were computed and differences between groups tested using independent-samples t tests. High vs low confidence diagnoses were compared using the pairedsamples t test. RESULTS:Eleven endoscopists without previous experience on optical diagnosis evaluated a total of 550 images (396 adenomatous, 154 non-adenomatous). Mean sensitivity, specificity and accuracy for diagnosing adenomas were 79.3%, 85.7% and 81.1%, respectively. No significant differences were found between gastroenterologists and trainees regarding performances of optical diagnosis (mean accuracy 78.0%vs 82.9%,P = 0.098). Diminutive lesions were predicted with a lower mean accuracy as compared to non-diminutive lesions (74.2% vs 93.1%, P = 0.008). A total of 446 (81.1%) diagnoses were made with high confidence. High confidence diagnoses corresponded to a significantly higher mean accuracy than low confidence diagnoses (84.0% vs 64.3%, P = 0.008). A total of 319 (58.0%) images were evaluated as having excellent quality. Considering excellent quality images in conjunction with high confidence diagnosis, overall accuracy increased to 92.8%. CONCLUSION:After a single training session, endoscopists with varying levels of experience can already provide optical diagnosis with an accuracy of 84.0%.
文摘There is an increasing demand for supporting high-quality real-time audiovisual services for the next generation wired and wireless networks. However, due to variety of bandwidths of different networks, it is a great challenge for deployment. In this paper, a novel high-definition (HD) video transmission system was proposed which depends upon reliable compound multicast protocols and QoS control over the various kinds of networks. This system detects client's network condition and assigns it to a proper proxy. Each proxy is capable of detecting network parameters and adaptively tuning such transport parameters as bit rate, video resolution, frame rate and QoS mechanisms to this condition. It also provides FEC error recovery under consideration of characteristics of MPEG4 video codec. Our simulation demonstrates that different network clients such as ADSL, CERNET, and CERNET2 can receive more video reliability with less delay.
