Diffusion tensor imaging plays an important role in the accurate diagnosis and prognosis of spinal cord diseases. However, because of technical limitations, the imaging sequences used in this technique cannot reveal t...Diffusion tensor imaging plays an important role in the accurate diagnosis and prognosis of spinal cord diseases. However, because of technical limitations, the imaging sequences used in this technique cannot reveal the fine structure of the spinal cord with precision. We used the readout segmentation of long variable echo-trains（RESOLVE） sequence in this cross-sectional study of 45 healthy volunteers aged 20 to 63 years. We found that the RESOLVE sequence significantly increased the resolution of the diffusion images and improved the median signal-to-noise ratio of the middle（C4–6） and lower（C7–T1） cervical segments to the level of the upper cervical segment. In addition, the values of fractional anisotropy and radial diffusivity were significantly higher in white matter than in gray matter. Our study verified that the RESOLVE sequence could improve resolution of diffusion tensor imaging in clinical applications and provide accurate baseline data for the diagnosis and treatment of cervical spinal cord diseases.展开更多
A rainstorm which occurred between May 22and 23, 2014 in Guangdong Province of the South Chinawarm region was simulated by using the ARW-WRFmodel. Three ＂echo-trainings＂ over the rainstorm centerwere analyzed and th...A rainstorm which occurred between May 22and 23, 2014 in Guangdong Province of the South Chinawarm region was simulated by using the ARW-WRFmodel. Three ＂echo-trainings＂ over the rainstorm centerwere analyzed and the results of both the simulation andobservational analysis showed that this rainstorm processwas composed of three stages. In the first stage, gravitywaves triggered the simultaneous but relatively indepen-dent formation of linearwhich moved toward theconvection and convective cells,northeast through the rain center,thus creating the echo-training. In the second stage, withthe formation of cold outflow, new convective cells werecontinuously created in the southwest and northwest of therain area and then gradually moved to merge into thenortheast rain area, thus forming a new echo-training. Inthe third stage, multiple rain bands above the rain areamoved southeastward and passed through the strongestprecipitation center, thus creating the third echo-training.The model simulation showed that a substantial warmingappeared at 900 hPa before the convective initiation,leading to the formation of a stable layer below 900 hPa,which was the primary cause for the gravity waves thattriggered the multiple convective cells. The multipleconvective cells formed the convective line, followingwhich new convection was formed from the cold outflowin its southwest and northwest directions. The newconvection in the southwest maintained the rain band;however, the new convection in the northwest, combinedwith the rain band of the north, formed a large radarreflectivity area and consequently, a larger MCS.展开更多
利用常规气象观测、地面加密自动站和多普勒天气雷达资料,结合WRF(Weather Research and Forecast)模式模拟资料,对2015年6月26—28日长江中下游的一次梅雨锋暴雨过程中尺度对流系统(Mesoscale Convective System,MCS)的组织特征和对流...利用常规气象观测、地面加密自动站和多普勒天气雷达资料,结合WRF(Weather Research and Forecast)模式模拟资料,对2015年6月26—28日长江中下游的一次梅雨锋暴雨过程中尺度对流系统(Mesoscale Convective System,MCS)的组织特征和对流触发条件进行分析。结果表明:1)暴雨过程线状MCS在发展初期表现为东西向雨带不断的"后部建立"以及随后对流单体的"列车效应";在发展成熟期,对流单体向东北—西南向发展,形成多个近乎平行的东北—西南向短雨带。呈现2种尺度的对流组织方式:新生对流单体沿着单个雨带向东北方向的"列车效应"和短雨带沿着线状M CS向东平流的"列车带"效应。2)低空急流的持续加强为对流的发生发展提供了条件性不稳定和对流有效位能,偏南暖湿气流在向东北推进的过程中,在风速辐合处被强迫抬升至自由对流高度,释放不稳定能量,触发对流。3)对流雨带内近地面向南的冷出流与低层西南暖湿气流的持续交汇和相互作用有利于新单体生成发展,使雨带得以维持。展开更多
目的探讨脊髓型颈椎病诊断中3.0T高清弥散多次激发弥散加权成像(readout segmentation of long variable echo-trains,RESOLVE-DWI)的应用价值。方法选取本院收治的脊髓型颈椎病患者60例为观察组,于同期本院接收的健康体检者中选取60例...目的探讨脊髓型颈椎病诊断中3.0T高清弥散多次激发弥散加权成像(readout segmentation of long variable echo-trains,RESOLVE-DWI)的应用价值。方法选取本院收治的脊髓型颈椎病患者60例为观察组,于同期本院接收的健康体检者中选取60例为对照组,均采用3.0T高清弥散RESOLVE-DWI序列进行检查,对比分析两组检查情况。结果观察组病变或受压部位的ADC值是(1.35±0.13)×10^-3 mm^2/s,比对照组的(1.01±0.03)×10^-3 mm^2/s及观察组中相对正常部位的(1.02±0.02)×10^-3 mm^2/s高,差异有统计学意义(P<0.05);RESOLVE-DWI序列图像质量评分较T 2WI高,差异有统计学意义(P<0.05);RESOLVE-DWI的敏感性为96.7%,特异性为95.0%,分别较T 2WI的敏感性91.7%、特异性88.3%高,差异有统计学意义(P<0.05)。结论3.0T高清弥散RESOLVE-DWI序列图像质量高,可对脊髓、解剖结构进行清晰显示,应用于脊髓型颈椎病诊断中准确率、敏感性高,值得选用。展开更多
文摘Diffusion tensor imaging plays an important role in the accurate diagnosis and prognosis of spinal cord diseases. However, because of technical limitations, the imaging sequences used in this technique cannot reveal the fine structure of the spinal cord with precision. We used the readout segmentation of long variable echo-trains（RESOLVE） sequence in this cross-sectional study of 45 healthy volunteers aged 20 to 63 years. We found that the RESOLVE sequence significantly increased the resolution of the diffusion images and improved the median signal-to-noise ratio of the middle（C4–6） and lower（C7–T1） cervical segments to the level of the upper cervical segment. In addition, the values of fractional anisotropy and radial diffusivity were significantly higher in white matter than in gray matter. Our study verified that the RESOLVE sequence could improve resolution of diffusion tensor imaging in clinical applications and provide accurate baseline data for the diagnosis and treatment of cervical spinal cord diseases.
文摘A rainstorm which occurred between May 22and 23, 2014 in Guangdong Province of the South Chinawarm region was simulated by using the ARW-WRFmodel. Three ＂echo-trainings＂ over the rainstorm centerwere analyzed and the results of both the simulation andobservational analysis showed that this rainstorm processwas composed of three stages. In the first stage, gravitywaves triggered the simultaneous but relatively indepen-dent formation of linearwhich moved toward theconvection and convective cells,northeast through the rain center,thus creating the echo-training. In the second stage, withthe formation of cold outflow, new convective cells werecontinuously created in the southwest and northwest of therain area and then gradually moved to merge into thenortheast rain area, thus forming a new echo-training. Inthe third stage, multiple rain bands above the rain areamoved southeastward and passed through the strongestprecipitation center, thus creating the third echo-training.The model simulation showed that a substantial warmingappeared at 900 hPa before the convective initiation,leading to the formation of a stable layer below 900 hPa,which was the primary cause for the gravity waves thattriggered the multiple convective cells. The multipleconvective cells formed the convective line, followingwhich new convection was formed from the cold outflowin its southwest and northwest directions. The newconvection in the southwest maintained the rain band;however, the new convection in the northwest, combinedwith the rain band of the north, formed a large radarreflectivity area and consequently, a larger MCS.
文摘利用常规气象观测、地面加密自动站和多普勒天气雷达资料,结合WRF(Weather Research and Forecast)模式模拟资料,对2015年6月26—28日长江中下游的一次梅雨锋暴雨过程中尺度对流系统(Mesoscale Convective System,MCS)的组织特征和对流触发条件进行分析。结果表明:1)暴雨过程线状MCS在发展初期表现为东西向雨带不断的"后部建立"以及随后对流单体的"列车效应";在发展成熟期,对流单体向东北—西南向发展,形成多个近乎平行的东北—西南向短雨带。呈现2种尺度的对流组织方式:新生对流单体沿着单个雨带向东北方向的"列车效应"和短雨带沿着线状M CS向东平流的"列车带"效应。2)低空急流的持续加强为对流的发生发展提供了条件性不稳定和对流有效位能,偏南暖湿气流在向东北推进的过程中,在风速辐合处被强迫抬升至自由对流高度,释放不稳定能量,触发对流。3)对流雨带内近地面向南的冷出流与低层西南暖湿气流的持续交汇和相互作用有利于新单体生成发展,使雨带得以维持。
