ArcGIS for Android(AA)技术作为新型移动电子地图技术具有功能丰富、定制性强、数据类型多样等优势,极大扩充了移动电子地图的应用场景。针对AA技术注记功能中无效加载量多、注记相互遮盖、要素类型限制的问题,该文提出了一种基于AA技...ArcGIS for Android(AA)技术作为新型移动电子地图技术具有功能丰富、定制性强、数据类型多样等优势,极大扩充了移动电子地图的应用场景。针对AA技术注记功能中无效加载量多、注记相互遮盖、要素类型限制的问题,该文提出了一种基于AA技术的移动端电子地图动态注记新方法。通过窗口搜索和4分区筛选两个主要步骤,实现多余要素过滤与注记均匀分布。同时,从遮盖性与加载效率两方面设计实验进行分区因子影响对比分析,验证了该方法的正确性与可行性。展开更多
Most efficient indeces and query techniques over XML （extensible markup language） data are based on a certain labeling scheme, which can quickly determine ancestor-descendant and parent-child relationship between tw...Most efficient indeces and query techniques over XML （extensible markup language） data are based on a certain labeling scheme, which can quickly determine ancestor-descendant and parent-child relationship between two nodes. The current basic labeling schemes such as containment scheme and prefix scheme cannot avoid re- labeling when XML documents are updated. After analyzing the essence of existing dynamic XML labels such as compact dynamic binary string （CDBS） and vector encoding, this paper gives a common unifying framework for the numeric-based generalized dynamic label, which can be implemented into a variety of dynamic labels according to the different user-defined value comparison methods. This paper also proposes a novel dynamic labeling scheme called radical sign label. Extensive experiments show that the radical sign label performs well for the initialization, insertion and query operations, and especially for skewed insertion where the storage cost of the radical sign label is better than that of former methods.展开更多
目的比较多参数三维假连续式动脉自旋标记灌注成像(3D p CASL)与动态磁敏感增强灌注成像(DSC PWI)对短暂性脑缺血发作(TIA)责任病灶的检出率。方法比较39例临床诊断TIA患者,并在首次发作24 h内进行磁共振检查。扫描序列包括常规头颅MR...目的比较多参数三维假连续式动脉自旋标记灌注成像(3D p CASL)与动态磁敏感增强灌注成像(DSC PWI)对短暂性脑缺血发作(TIA)责任病灶的检出率。方法比较39例临床诊断TIA患者,并在首次发作24 h内进行磁共振检查。扫描序列包括常规头颅MR成像、MRA(MRA),DWI、3D p CASL(选取两个标记延迟时间post-labeling time,PLD,PLD=1.5 s及PLD=2.5 s),DSC PWI。后处理获取3D p CASL的脑血流(CBF)图像和DSC PWI的Tmax图像。比较不同灌注方法与MRA及DWI结合法对于缺血病灶检出率和缺血面积。结果 TIA患者的缺血病灶检出率,3D p CASL(PLD1.5 s及PLD2.5 s)的CBF图像与DSC PWI Tmax对比无差异;3D p CASL(PLD1.5 s)的CBF图像对于缺血的检出率高于MRA结合DWI法;DSC PWI Tmax、3D p CASL(PLD2.5 s)CBF与MRA结合DWI法无差异。显示低灌注面积,3D p CASL(PLD1.5 s)的CBF图像显示的面积最大,其次是DSC PWI Tmax,而3D p CASL(PLD2.5 s)的CBF图像显示的低灌注面积最小。结论 3D p CASL脑灌注成像技术无创、快速、可重复性强,推荐作为临床可疑TIA患者的影像筛查手段,不同PLD的3D p CASL序列对于病灶的检出及缺血面积的显示有差异,选择较短PLD有可能提高病灶的检出率。展开更多
Summary： The purpose of this study was to quantitatively analyze the relationship between three di- mensional arterial spin labeling （3D-ASL） and dynamic susceptibility contrast-enhanced perfusion weighted imaging ...Summary： The purpose of this study was to quantitatively analyze the relationship between three di- mensional arterial spin labeling （3D-ASL） and dynamic susceptibility contrast-enhanced perfusion weighted imaging （DSC-PWI） in ischemic stroke patients. Thirty patients with ischemic stroke were in- cluded in this study. All subjects underwent routine magnetic resonance imaging scanning, diffusion weighted imaging （DWI）, magnetic resonance angiography （MRA）, 3D-ASL and DSC-PWI on a 3.0T MR scanner. Regions of interest （ROIs） were drawn on the cerebral blood flow （CBF） maps （derived from ASL） and multi-parametric DSC perfusion maps, and then, the absolute and relative values of ASL-CBF, DSC-derived CBF, and DSC-derived mean transit time （MTT） were calculated. The rela- tionships between ASL and DSC parameters were analyzed using Pearson＇s correlation analysis. Re- ceiver operative characteristic （ROC） curves were performed to define the thresholds of relative value of ASL-CBF （rASL） that could best predict DSC-CBF reduction and MTT prolongation. Relative ASL better correlated with CBF and MTT in the anterior circulation with the Pearson correlation coefficients （R） values being 0.611 （P〈0.001） and-0.610 （P〈0.001） respectively. ROC curves demonstrated that when rASL 〈0.585, the sensitivity, specificity and accuracy for predicting ROIs with rCBF〈0.9 were 92.3%, 63.6% and 76.6% respectively. When rASL 〈0.952, the sensitivity, specificity and accuracy for predicting ROIs rMTT〉I.0 were 75.7%, 89.2% and 87.8% respectively. ASL-CBF map has better linear correlations with DSC-derived parameters （DSC-CBF and MTT） in anterior circulation in ischemic stroke patients. Additionally, when rASL is lower than 0.585, it could predict DSC-CBF decrease with moderate accuracy. IfrASL values range from 0.585 to 0.952, we just speculate the prolonged MTT.展开更多
文摘ArcGIS for Android(AA)技术作为新型移动电子地图技术具有功能丰富、定制性强、数据类型多样等优势,极大扩充了移动电子地图的应用场景。针对AA技术注记功能中无效加载量多、注记相互遮盖、要素类型限制的问题,该文提出了一种基于AA技术的移动端电子地图动态注记新方法。通过窗口搜索和4分区筛选两个主要步骤,实现多余要素过滤与注记均匀分布。同时,从遮盖性与加载效率两方面设计实验进行分区因子影响对比分析,验证了该方法的正确性与可行性。
基金the National Major Projects on Science and Technology(No.2010ZX01042-002-003-004)the National Basic Research Program (973) of China(No.2010CB328106)+2 种基金the National Natural Science Foundation of China(No. 61170085)the Program for New Century Excellent Talents in China(No.NCET-10-0388)the Shanghai Leading Academic Discipline Project(No.B412)
文摘Most efficient indeces and query techniques over XML （extensible markup language） data are based on a certain labeling scheme, which can quickly determine ancestor-descendant and parent-child relationship between two nodes. The current basic labeling schemes such as containment scheme and prefix scheme cannot avoid re- labeling when XML documents are updated. After analyzing the essence of existing dynamic XML labels such as compact dynamic binary string （CDBS） and vector encoding, this paper gives a common unifying framework for the numeric-based generalized dynamic label, which can be implemented into a variety of dynamic labels according to the different user-defined value comparison methods. This paper also proposes a novel dynamic labeling scheme called radical sign label. Extensive experiments show that the radical sign label performs well for the initialization, insertion and query operations, and especially for skewed insertion where the storage cost of the radical sign label is better than that of former methods.
文摘目的比较多参数三维假连续式动脉自旋标记灌注成像(3D p CASL)与动态磁敏感增强灌注成像(DSC PWI)对短暂性脑缺血发作(TIA)责任病灶的检出率。方法比较39例临床诊断TIA患者,并在首次发作24 h内进行磁共振检查。扫描序列包括常规头颅MR成像、MRA(MRA),DWI、3D p CASL(选取两个标记延迟时间post-labeling time,PLD,PLD=1.5 s及PLD=2.5 s),DSC PWI。后处理获取3D p CASL的脑血流(CBF)图像和DSC PWI的Tmax图像。比较不同灌注方法与MRA及DWI结合法对于缺血病灶检出率和缺血面积。结果 TIA患者的缺血病灶检出率,3D p CASL(PLD1.5 s及PLD2.5 s)的CBF图像与DSC PWI Tmax对比无差异;3D p CASL(PLD1.5 s)的CBF图像对于缺血的检出率高于MRA结合DWI法;DSC PWI Tmax、3D p CASL(PLD2.5 s)CBF与MRA结合DWI法无差异。显示低灌注面积,3D p CASL(PLD1.5 s)的CBF图像显示的面积最大,其次是DSC PWI Tmax,而3D p CASL(PLD2.5 s)的CBF图像显示的低灌注面积最小。结论 3D p CASL脑灌注成像技术无创、快速、可重复性强,推荐作为临床可疑TIA患者的影像筛查手段,不同PLD的3D p CASL序列对于病灶的检出及缺血面积的显示有差异,选择较短PLD有可能提高病灶的检出率。
基金supported by grants from the 12th Five-year Science and Technology Support Program of China(No.2011BAI08B10)the National Natural Science Foundation of China(No.81171308,No.81570462)
文摘Summary： The purpose of this study was to quantitatively analyze the relationship between three di- mensional arterial spin labeling （3D-ASL） and dynamic susceptibility contrast-enhanced perfusion weighted imaging （DSC-PWI） in ischemic stroke patients. Thirty patients with ischemic stroke were in- cluded in this study. All subjects underwent routine magnetic resonance imaging scanning, diffusion weighted imaging （DWI）, magnetic resonance angiography （MRA）, 3D-ASL and DSC-PWI on a 3.0T MR scanner. Regions of interest （ROIs） were drawn on the cerebral blood flow （CBF） maps （derived from ASL） and multi-parametric DSC perfusion maps, and then, the absolute and relative values of ASL-CBF, DSC-derived CBF, and DSC-derived mean transit time （MTT） were calculated. The rela- tionships between ASL and DSC parameters were analyzed using Pearson＇s correlation analysis. Re- ceiver operative characteristic （ROC） curves were performed to define the thresholds of relative value of ASL-CBF （rASL） that could best predict DSC-CBF reduction and MTT prolongation. Relative ASL better correlated with CBF and MTT in the anterior circulation with the Pearson correlation coefficients （R） values being 0.611 （P〈0.001） and-0.610 （P〈0.001） respectively. ROC curves demonstrated that when rASL 〈0.585, the sensitivity, specificity and accuracy for predicting ROIs with rCBF〈0.9 were 92.3%, 63.6% and 76.6% respectively. When rASL 〈0.952, the sensitivity, specificity and accuracy for predicting ROIs rMTT〉I.0 were 75.7%, 89.2% and 87.8% respectively. ASL-CBF map has better linear correlations with DSC-derived parameters （DSC-CBF and MTT） in anterior circulation in ischemic stroke patients. Additionally, when rASL is lower than 0.585, it could predict DSC-CBF decrease with moderate accuracy. IfrASL values range from 0.585 to 0.952, we just speculate the prolonged MTT.
