This research compares the potential of SRTM-V4.1 and ASTER-V2.1 with 30-m pixel size to derive topographic attributes （elevation, slopes, aspects, and flow accumulation） and hydrologic indices such as STI （sedimen...This research compares the potential of SRTM-V4.1 and ASTER-V2.1 with 30-m pixel size to derive topographic attributes （elevation, slopes, aspects, and flow accumulation） and hydrologic indices such as STI （sediment transport index）, CTI （compound topographic index） and SPI （stream power index） to detect areas associated with flash floods cansed by rainfall storms and sediment accumulation. The study area is Guelmim city in Morocco, which has been flooded several times over the past 50 years, and which was declared a ＂disaster area＂ in December 2014 after violent rainfall storms killed 46 people and caused significant damage to the infrastructure. The obtained results indicate that the SRTM DEM performs better than ASTER in terms of micro-topography, hydrologic-network and structural information characterization. In addition, with reference to a topographic contours map （1：50000）, the derived global height surfaces accuracies are ＋3.15 m and 4-9.17 m for SRTM and ASTER, respectively. These accuracies are significantly influenced by topography; errors are larger （SRTM = 11.34 m, ASTER = 19.20 m） for high altitude terrain with strong slopes, while they are smaller （SRTM = 1.92 m, ASTER = 3.76 m） in the low to medium-relief areas with indulgent slopes. Moreover, all the considered hydrological indices are significantly characterized with SRTM compared to ASTER. They demonstrated that the rainfall and the topographic morphology are the major contributing factors in flash flooding and catastrophic inundation in this area. The runoff waterpower delivers vulnerable topsoil and contributes strongly to the erosion and transport of soil material and sediment to the plain areas through waterpower and gravity. Likewise, the role of the lithology associated with the terrain morphology is decisive in the erosion risk and land degradation in this region.展开更多
目的探讨基于双参数磁共振成像(biparametric magnetic resonance imaging,bp-MRI)的前列腺影像报告和数据系统2.1版(prostate imaging report and data system version 2.1,PI-RADS v2.1)联合前列腺特异性抗原密度(prostate specific a...目的探讨基于双参数磁共振成像(biparametric magnetic resonance imaging,bp-MRI)的前列腺影像报告和数据系统2.1版(prostate imaging report and data system version 2.1,PI-RADS v2.1)联合前列腺特异性抗原密度(prostate specific antigen density,PSAD)鉴别诊断总前列腺特异性抗原(total prostate specific antigen,tPSA)4~20 ng/mL临床显著性前列腺癌(clinically significant prostate cancer,csPCa)的价值及风险分层。材料与方法回顾性分析了宁夏医科大学总医院2017年10月至2023年6月304例PSA 4~20 ng/mL前列腺疾病患者的bp-MRI图像和临床资料。根据病理结果分为csPCa组(Gleason评分≥7分,n=66)和非csPCa(Gleason评分<7分及良性疾病,n=238)。经单因素、多因素logistic回归分析筛选独立危险因子并建立联合模型,再用决策曲线分析(decision curve analysis,DCA)其临床净效益。以受试者工作特征(receiver operating characteristic,ROC)曲线下面积(area under the curve,AUC)比较独立危险因子与联合模型的诊断效能,并对独立危险因子进行等级划分和组合。结果联合模型(PI-RADS v2.1+PSAD)的诊断效能最好(AUC为0.901,95%CI:0.858~0.944)。将PI-RADS v2.1与PSAD等级划分并组合,当PI-RADS v2.1≤2且PSAD≤0.15 ng/mL^(2),csPCa阳性率为0%;当PI-RADS v2.1为3分且PSAD<0.30 ng/mL^(2)时,csPCa阳性率<15%;当PI-RADS v2.1为4~5分且PSAD为0.15~0.29 ng/mL^(2)时,csPCa阳性率为46.5%;当PI-RADS v2.1为4~5分且PSAD≥0.30 ng/mL^(2)时,csPCa阳性率高达81.3%。结论PI-RAD v2.1≤2或PI-RAD v2.1=3且PSAD值<0.30 ng/ml2的患者可避免不必要的活检。PI-RADS v2.1联合PSAD能显著提高tPSA 4~20 ng/mL csPCa的诊断效能,将二者联合有助于穿刺前对csPCa的患者进行风险评估,以减少部分患者不必要的穿刺,并为临床提供一定的决策指导。展开更多
文摘This research compares the potential of SRTM-V4.1 and ASTER-V2.1 with 30-m pixel size to derive topographic attributes （elevation, slopes, aspects, and flow accumulation） and hydrologic indices such as STI （sediment transport index）, CTI （compound topographic index） and SPI （stream power index） to detect areas associated with flash floods cansed by rainfall storms and sediment accumulation. The study area is Guelmim city in Morocco, which has been flooded several times over the past 50 years, and which was declared a ＂disaster area＂ in December 2014 after violent rainfall storms killed 46 people and caused significant damage to the infrastructure. The obtained results indicate that the SRTM DEM performs better than ASTER in terms of micro-topography, hydrologic-network and structural information characterization. In addition, with reference to a topographic contours map （1：50000）, the derived global height surfaces accuracies are ＋3.15 m and 4-9.17 m for SRTM and ASTER, respectively. These accuracies are significantly influenced by topography; errors are larger （SRTM = 11.34 m, ASTER = 19.20 m） for high altitude terrain with strong slopes, while they are smaller （SRTM = 1.92 m, ASTER = 3.76 m） in the low to medium-relief areas with indulgent slopes. Moreover, all the considered hydrological indices are significantly characterized with SRTM compared to ASTER. They demonstrated that the rainfall and the topographic morphology are the major contributing factors in flash flooding and catastrophic inundation in this area. The runoff waterpower delivers vulnerable topsoil and contributes strongly to the erosion and transport of soil material and sediment to the plain areas through waterpower and gravity. Likewise, the role of the lithology associated with the terrain morphology is decisive in the erosion risk and land degradation in this region.
