Liver segmentation in MRI: A fully automatic method based on stochastic partitions

There are few fully automated methods for liver segmentation in magnetic resonance images (MRI) despite the benefits of this type of acquisition in comparison to other radiology techniques such as computed tomography (CT). Motivated by medical requirements, liver segmentation in MRI has been carried out. For this purpose, we present a new method for liver segmentation based on the watershed transform and stochastic partitions. The classical watershed over-segmentation is reduced using a marker-controlled algorithm. To improve accuracy of selected contours, the gradient of the original image is successfully enhanced by applying a new variant of stochastic watershed. Moreover, a final classifier is performed in order to obtain the final liver mask. Optimal parameters of the method are tuned using a training dataset and then they are applied to the rest of studies (17 datasets). The obtained results (a Jaccard coefficient of 0.91 ± 0.02) in comparison to other methods demonstrate that the new variant of stochastic watershed is a robust tool for automatic segmentation of the liver in MRI.     

Assessment of contaminants transport in a watershed affected by acid mine drainage,by coupling hydrological and geochemical modeling tools

Erini Stream (Thrace, northeastern Greece) is adversely affected by the presence of an abandoned mixed sulfide mine located in the upper watershed. The GIS based model SWAT (Soil Water and Assessment Tool) was applied to characterize hydrologic processes in the watershed. Model performance was evaluated by comparing the simulation results with field data including flow and concentration measurements from 12 monitoring points, for the time period from June 2005 to July 2006. Flow rate results indicated good agreement between simulated and measured data, with coefficient correlations R² in the range of 0.74–0.89. Simulation was focused on the dispersion of three pollutants, Zn, Cd and Mn. Using SWAT alone, simulation results systematically overestimated pollutants levels in Erini Stream.Geochemical model PHREEQC was used in combination with SWAT to obtain more accurate predictions regarding contaminants concentrations along the course of Erini Stream. The profiles of main metal contaminants, i.e. Zn, Cd and Mn, under wet conditions, were described with satisfactory precision assuming equilibrium with the carbonate minerals ZnCO₃·H₂O and otavite and partial supersaturation with respect to rhodochrosite. However, precipitation of discrete carbonate phases does not seem to be the predominant attenuation mechanism under dry conditions. Coprecipitation or sorption on the surface of precipitating calcite is another potential removal mechanism under these conditions.The methodology presented allows the reliable assessment of acid mine drainage impacts in the downstream aquatic environment and the design of effective measures for its mitigation based on an optimized number of monitoring data.     

最大熵方法在香溪河流域径流分析中的应用

香溪河流域是三峡库区的代表性流域,研究其径流量变化规律有重要意义,但目前尚缺乏对月尺度下各类径流统计量的分析。对此,以香溪河流域兴山水文站近40年（1969~2008年）径流量为基础,利用最大熵方法分析了香溪河流域的月径流变化特征。结果表明,最大熵方法可有效模拟香溪河流域的月径流量概率分布,体现其统计特征,优于P Ⅲ型分布;香溪河流域具有显著的丰枯季节变化,且平均月径流量最高点发生了变异;香溪河流域的月径流量存在缓慢下降的趋势,且1、5、9、10、12月份发生了变异。研究结果为水利工程规划、设计提供了依据。     

Associations among pathogenic bacteria, parasites, and environmental and land use factors in multiple mixed-use watersheds

Over a five year period (2004-08), 1171 surface water samples were collected from up to 24 sampling locations representing a wide range of stream orders, in a river basin in eastern Ontario, Canada. Water was analyzed for Cryptosporidium oocysts and Giardia cyst densities, the presence of Salmonella enterica subspecies enterica, Campylobacter spp., Listeria monocytogenes, and Escherichia coli O157:H7. The study objective was to explore associations among pathogen densities/occurrence and objectively defined land use, weather, hydrologic, and water quality variables using CART (Classification and Regression Tree) and binary logistical regression techniques. E. coli O157:H7 detections were infrequent, but detections were related to upstream livestock pasture density; 20% of the detections were located where cattle have access to the watercourses. The ratio of detections:non-detections for Campylobacter spp. was relatively higher (>1) when mean air temperatures were 6% below mean study period temperature values (relatively cooler periods). Cooler water temperatures, which can promote bacteria survival and represent times when land applications of manure typically occur (spring and fall), may have promoted increased frequency of Campylobacter spp. Fifty-nine percent of all Salmonella spp. detections occurred when river discharge on a branch of the river system of Shreve stream order = 9550 was >83 percentile. Hydrological events that promote off farm/off field/in stream transport must manifest themselves in order for detection of Salmonella spp. to occur in surface water in this region. Fifty seven percent of L. monocytogenes detections occurred in spring, relative to other seasons. It was speculated that a combination of winter livestock housing, silage feeding during winter, and spring application of manure that accrued during winter, contributed to elevated occurrences of this pathogen in spring. Cryptosporidium and Giardia oocyst and cyst densities were, overall, positively associated with surface water discharge, and negatively associated with air/water temperature during spring-summer-fall. Yet, some of the highest Cryptosporidium oocyst densities were associated with low discharge conditions on smaller order streams, suggesting wildlife as a contributing fecal source. Fifty six percent of all detections of ≥2 bacteria pathogens (including Campylobacter spp., Salmonella spp., and E. coli O157:H7) in water was associated with lower water temperatures (<∼14 °C; primarily spring and fall) and when total rainfall the week prior to sampling was >∼27 mm (62 percentile). During higher water temperatures (>∼14 °C), a higher amount of weekly rainfall was necessary to promote detection of ≥2 pathogens (primarily summer; weekly rainfall ∼>42 mm (>77 percentile); 15% of all ≥2 detections). Less rainfall may have been necessary to mobilize pathogens from adjacent land, and/or in stream sediments, during cooler water conditions; as these are times when manures are applied to fields in the area, and soil water contents and water table depths are relatively higher. Season, stream order, turbidity, mean daily temperature, surface water discharge, cropland coverage, and nearest upstream distance to a barn and pasture were variables that were relatively strong and recurrent with regard to discriminating pathogen presence and absence, and parasite densities in surface water in the region.     

交互式流域算法在医学图像分割中的应用

本文首先介绍了流域算法的基本思想、基本原理以及流域变换过程中所存在的问题,回顾了为加快流域变换的计算而进行的大量研究工作,然后利用区域信息、结合交互式流域变换分割医学图像,实验结果表明该方法能有效地解决流域变换中的过度分割问题。     

Evaluation of the Biocriteria of Streams in the San Diego Hydrologic Region

In this study, bioassessment data collected between 1998 and 2005 were synthesized and analyzed for streams and rivers throughout the San Diego Hydrologic Region to provide a spatial and temporal context for the results of several monitoring projects conducted between 1998 and 2005 and to ascertain the applicability of the Southern California benthic macroinvertebrate index of biological integrity (SoCal B-IBI) to the region’s streams. The water quality of the sites studied in the region, as reflected by temporal and spatial analyses of SoCal B-IBI scores, was found to be quite poor. When streams were analyzed individually most showed stable scores over the time frame of the study with some showing better scores in the fall. Spatially, scores were found to be better farther away from the coast in the upstream reaches of the watersheds. This study further explored the applicability of the SoCal B-IBI to a focused geographic region by demonstrating the necessity of each component metric to the assignment of biological condition. Although all component metric scores were deemed to be necessary, the percent intolerant individuals score had a more significant effect in driving impairment. The analysis of the component metrics of the SoCal B-IBI provides useful insights to the changes in scores among and between the sampled sites in the region’s watersheds. Based on this study, natural resource management agencies responsible for managing water quality should incorporate regular measures of biological integrity into their water quality programs to ascertain regional and temporal trends.     

基于分数阶微分、水平集及分水岭的铅锌浮选图像分割

针对铅锌浮选气泡暗颜色、细节弱、分割难的特征,提出了一种新的图像分割算法。该算法分成三个部分： 气泡边界增强： 基于分形学改进分数阶微分算法,主要是根据图像的纹理特性自动确定分数阶微分的非整数阶数,以自适应分数阶微分算法增强气泡边缘; 气泡亮点区域提取： 在改进传统的水平集算法基础上,进行精确的气泡亮点区域的提取,克服了全局自动阈值算法在提取气泡亮点时存在的缺陷; 图像分割： 利用内外标记修正梯度图像, 最后运用分水岭算法对浮选图像进行分割。对于不同铅锌矿大小气泡图像的实验,并通过与多种传统的图像分割算法分析比较,实验结果表明新算法不仅提高了浮选气泡图像的分割精度,并且有效地减少了传统图像分割算法的过分割问题,本文算法对于浮选气泡具有良好的分割效果。     

GIS在西沟小流域中的应用

黄土高原水土保持二期世行贷款项目管理,力求在高质量、高标准、自动化方面有新的突破.内蒙古自治区石拐区运用地理信息系统EzMap软件,在西沟小流域中进行流域空间分析,获取数据,进行相应数据库管理并绘制和打印所需图件,使小流域治理在规划及实施管理方面更加规范化、科学化、现代化.     

Watershed from propagated markers: An interactive method to morphological object segmentation in image sequences

In this paper, it is introduced an interactive method to object segmentation in image sequences, by combining classical morphological segmentation with motion estimation – the watershed from propagated markers. In this method, the objects are segmented interactively in the first frame and the mask generated by its segmentation provides the markers that will be used to track and segment the object in the next frame. Besides the interactivity, the proposed method has the following important characteristics: generality, rapid response and progressive manual edition. This paper also introduces a new benchmark to do quantitative evaluation of assisted object segmentation methods applied to image sequences. The evaluation is done according to several criteria such as the robustness of segmentation and the easiness to segment the objects through the sequence.