医学图像归档与传输系统（PACS）

概述：PACS（PictureArchivingandCommunicationSystems）即图像归档与传输系统,是医院的医学图像信息管理系统,图像主要来源于医院的放射医疗设备（如X-CT、UFCT、MAI机以及PET等）。传统的放射科医生的诊断方式主要是根据由特定影像设备产生的胶片,凭借医生多年的诊断经验判断是否有病变及其具体情况。这种利用胶片的诊断和存储方式随着影像设备的不断更新换代已经越来越不适应医院的管理发展需要。随着计算机技术的飞速发展,使用计算机取代胶片保存手段应用于医院管理的想法已产生了,PACS正是这种思想发展的结果。PACS…     

不变矩特征在医学CT图像中的应用分析

本文以医学CT图像为研究对象,探讨不变矩特征在医学CT图像中的应用。首先实验验证不变矩特征所具有的旋转、平移、缩放等不变特性,其后以基于内容的医学图像检索为例,揭示不变矩特征在基于内容的医学图像检索中的应用原理,最后分析图像不变矩特征的应用场合。实验成果对不变矩特征在医学图像识别、图像匹配、形状分析、图像分割以及基于内容的图像检索等领域的应用具有推动作用。     

基于CV模型的CT图像分割研究

由于医学图像边缘模糊、不均匀性等特点,使用传统的Chan-Vese(CV)模型方法难以达到分割要求,同时该方法存在计算量大、分割速度慢的问题。本文提出了一种基于CV模型改进的分割算法,在水平集演化迭代过程中,根据当前主动轮廓线的位置,引入图像局部灰度信息,提高了水平集能量项的有效性和该模型的收敛速度,并提出了一种关于图像序列的分割方法。实验结果表明,运用本文提出的方法能够快速、准确地提取图像中感兴趣目标,是一种较为理想的医学图像分割方法。     

CT图像的质量分析与控制

本文论述了鉴定ＣＴ图像质量的标准,阐述了提高ＣＴ图像质量的各技术环节,为ＣＴ图像质量控制提出了有效的方法。     

建立医院间PACS系统的技术和实现

介绍了建立医院和医院之间PACS系统的意义;信息传输技术的不断发展,为建立院间PACS系统提供了物质基础,采用固定IP地址的中间存储空间和采用适当无损压缩方法是建立院间PACS系统的关键。     

欢迎订阅《中国体视学与图像分析》

《中国体视学与图像分析》是经国家出版署批准,中国科学技术协会主管、国家一级学会——中国体视学学会主办,全面反映中国体视学理论和图像应用技术研究的学术性和技术性综合刊物。主要报道国内外有关三维结构与图像的定量分析和表征的最新理论与方法,内容涉及体视学、图像分析、三维视觉、三维建模、三维成像与可视化.     

基于图像信息方法的南北地震带地震预测研究

图像信息法(PI)计算过程涉及地震活动性的归一化,因此针对地震活动性相似的地区PI预测效能较好.以南北地震带为研究区域,对图像信息法(PI)在南北地震带不同范围的预测效能进行了研究.采用中国地震台网中心提供的1970年以来中国地震目录,选取5年尺度的\"异常学习窗\"和\"预测时间窗\"以及1°×1°网格,以2017年以来发生的MS≥6地震为目标,通过ROC检验,对地震进行回溯性预测研究.研究结果显示:①PI方法对南北地震带南段、中段、北段区域进行计算的预测效能呈现逐渐降低的趋势,但幅度较小,显示PI方法的预测效能可能受到区域内地震活动性强度的影响.②PI方法对南北地震带分段计算的预测效能优于对整个南北地震带进行计算的预测效能.其中,把南北地震带北段、中段合起来作为一个计算区域时预测效能最好,南段、中段、北段预测效果次之,把中段、南段合起来作为一个计算区域时预测效能相对较低,南北地震带整体的预测效能最低.通过地震活动性对南北地震带进行区域划分能使得预测效能提高.③计算结果显示,滇西南永德—泸水地区、龙门山断裂南段附近存在\"热点\",未来5年内这些地区为MS≥6地震值得关注的重点区域.     

基于改进型图像信息方法的汶川地震前电离层参量时空特征研究

震前加速破坏阶段地壳岩石破裂过程中可能辐射电磁信号,提取与之相关的电磁信号异常有助于认识地震孕育及破坏过程,从而为防震减灾提供支持.本文提出了改进型图像信息方法(Modified Pattern Informatics Method,MPI方法),并用于汶川地震前电离层参量时空特征信息的提取.通过分析对比处理前后的DEMETER电磁卫星时空图像可以发现,原始时空图像一般存在季节性和空间性的变化规律,较难获得有意义的信息;而采用MPI方法处理后,则发现汶川大地震前,电离层参量存在明显的异常变化.从而,证明了MPI方法具有消除背景趋势、突出短期变化的能力,可以有效地提取强震相关的电磁前兆信息.     

基于光谱估计和图像重建的双能量CT迭代算法

已知的光谱信息对双能量CT（DECT）重建具有重要的意义,但在实际应用中,光谱信息很难直接获得,此外,双能量CT的重建算法对噪声敏感,因此,在重建算法中需要设计对应的噪声抑制方法来提升重建图像质量。本文提出了一种同时更新双能量CT估计光谱和重建图像的迭代方法,该方法不需要提前获得光谱信息,估计光谱和重建图像可以通过提出的算法同时获得。两组实验用来验证算法的有效性。实验结果表明,提出方法不仅能够准确估计光谱,也可以同时提升DECT重建图像质量。     

磁组构的分离与岩石构造变形分析

目前实验条件下获得的AMS（磁化率各向异性）是岩石内所有磁性矿物磁化率各向异性叠加的综合响应,详细的岩石磁学和构造地质学的综合分析表明常规AMS测试结果通常无法揭示岩石复杂的构造变形过程.本文综述了运用非磁滞剩磁各向异性（AARM）、低温AMS（LT-AMS）和高场AMS（HF-AMS）等实验方法对岩石AMS组分进行分离,可以定量获取不同磁性矿物的磁组构贡献,进而解释其不同的变形特征.在此基础上阐述了近年来针对不同磁性矿物组合的AMS分离方法的理论技术创新和进展及其在岩石构造变形特征分析中的应用前景,讨论了常见磁性矿物单晶的岩石磁学性质及各向异性度（P_j）与形状因子（T）在揭示岩石变形特征中的复杂性与局限性,最后举例并分析了磁组构分离技术在造山带岩石构造变形分析中的应用.

     

Radio Emission from Galactic Disks

This paper gives a short overview of the observational results on galactic magnetic fields. Interstellar magnetic fields, as deduced from multi-frequency polarization observations, show a well-ordered structure largely following the spiral arms. In some galaxies an axisymmetric spiral pattern dominates (the field being directed inwards), while others exhibit a dominant bisymmetric spiral field or mixed modes, as predicted from non-linear dynamo theory. As long as star formation activity is low, the magnetic fields are rather regular. Strong star formation leads to turbulent cloud motions and supernova explosions, which tangle the field, so that the radio emission is only weakly polarized. As a consequence the highest fractional polarizations and polarized intensities at centimeter wavelengths are found in interarm regions. At decimeter wavelengths, galactic disks become optically thick for polarized emission. In NGC 6946 the regular field is concentrated in narrow magnetic arms located in between the optical spiral arms. The field cannot simply be frozen into the gas and oriented by a density-wave flow. A galactic dynamo may provide a stable spiral pattern of the field, but non-axisymmetric models are still being developed.     

通用磁光盘驱动器在CT机上的应用

目的;以通用ＭＯＤ代替专用ＭＯＤ模块,解决ＣＴ机数据资料的存储问题。方法：用ＭＡＸＯＰＴＩＸＭＯＤ来代换ＰＩＯＮＥＥＲ ＭＯＤ。结果;很好的解决了ＣＴ机数据资料的存储问题,保证了ＣＴ数据的安全性。结论：ＭＡＸＯＰＴＩＸ ＭＯＤＳ可以成功地应用在ＳＹＴＥＣ４０００ＣＴ机上,成果很有推广价值。     

DRY-SEASON VARIABILITY IN SUSPENDED SEDIMENT CONCENTRATIONS IN THE SOUTH PASSAGE OF THE CHANGJIANG ESTUARY

This paper reports the results of continuous monitoring of turbidity, water depth, salinity (using an Optical Backscatter Sensor (OBS)), and current velocity (using a Current meter (SLC9-2)) in the South Passage of the Changjiang Estuary over a spring–neap period in February 2003 (dry season). The turbidity measured via OBS was closely correlated with the suspended sediment concentration (SSC), which was highly variable. Over the study period, the SSC in the middle layer ranged from 110 to 1400 mg/l. The minimum SSC occurred during a late ebb tide, and the maximum SSC occurred during a late flood tide. On average, the SSC was 1.5 times higher during flood tide than during ebb tide. Vertically within the water column, SSC increased downward, with the ratio of SSC measured near the bed to that measured at the surface ranging from 1.90 to 18.3. The temporal variability in SSC is jointly governed by tides and wind-induced waves, whereas the vertical variability in SSC is attributed to the effect of gravity and vertical water circulation.     

Linear collapse of spatially linear,three-dimensional,potential null points

The collapse of the magnetic field in the vicinity of a null point creates a large electrical current. Non-ideal effects in the surrounding plasma can then allow the onset of magnetic reconnection, which is important in many astrophysical phenomena. An elegant technique is used to show that spatially linear, initially potential, three-dimensional null points have a tendency to collapse with a growth of either the spine current or the fan current or a combination of both. The rate of collapse is determined for an incompressible plasma flow with open boundary conditions. An initial plasma flow affects the rate of collapse by speeding it up.     

Evolution of Magnetic Fields in Galaxies with Spiral Structure

We present simulations of the 3D nonlinear induction equation in order to investigate the temporal evolution of large-scale magnetic fields in spiral galaxies. Our model includes differential rotation, ambipolar diffusion and, based on small-scale turbulence, eddy diffusivity and the tensorial -effect with magnetic feedback. The nonaxisymmetric spiral pattern and – if considered – the vertical stratification of the galaxy are represented in its density and turbulence profile. Neglecting vertical stratification the lifetime and geometry of an initial magnetic field depend on the correlation time of interstellar turbulence _corr . Short correlation times increase the lifetime of the initial magnetic field, but the field is rapidly wound up. Its pitch-angles develop to zero. The magnetic field has disappeared after at most 1 to 1.5 Gyr. A resonance like phenomenon is found by tuning the pattern velocity of the galactic spiral. The simulations then show an exceptional amplification of the magnetic field in the case that the pattern speed and a magnetic drift velocity have similar values. Considering a vertical stratification we achieve sufficiently long living grand-designed magnetic fields excited by dynamo action. The behaviour and geometry of the resulting field is again significantly influenced by the correlation time _corr . Small values of _corr lead to axisymmetric fields with small pitch-angles and field-concentration between the spiral arms. Increasing the correlation time the solutions show larger pitch-angles; and depending on very large correlation times the galactic dynamo rather generates fields clearly within the spiral arms and having a bisymmetric structure.     

Rapid magnetic susceptibility measurement as a tracer to assess the erosion–deposition process using tillage homogenization and simple proportional models: A case study in northern of Morocco

Soil erosion is a significant threat in the Rif region in northern Morocco. Hence, accurate cartography of the phenomenon, magnitude, and extent of erosion in the area needs a simple, rapid, and economical method such as magnetic susceptibility (MS). The current study aims to: (i) determine the factors influencing the variation of soil MS, (ii) exploit MS to estimate soil loss using two approaches in different homogenous units characterized by the same climatic conditions with different edaphic characteristics (land use, slope, and lithology), and (iii) highlight the potential for using MS as a cheap and rapid tracer of a long term erosion and deposition processes. Mass-specific magnetic susceptibility at low (χ_lf) and high (χ_hf) frequencies were measured for 182 soil samples collected in the study area. A tillage homogenization (T-H) model and a simple proportional model (SPM) were applied on an undisturbed soil profile to predict the eroded soil depths for given cores. The results confirm that χ_lf is influenced by land use, slope, and soil type. Pedogenesis is the main factor affecting soil MS enhancement, indicated by homogenous magnetic mineralogy with a dominance of super-paramagnetic (SP) and stable single domain (SSD) magnetic grains. The study results show that higher soil losses have occurred in almost all the soil samples when applying the T-H model compared to application of the SPM. The SPM underestimates erosion due to its ignorance of the MS of the plow layers after erosion. The current study implies the high efficacy of magnetic susceptibility as the quick, easily measurable, simple, and cost-effective approach that can be used as an alternative technique for evaluating soil redistribution.     

Study on retrieve specified objects in massive remote sensing data

In this paper, we show that to retrieve specified objects in massive remote sensing data set is very important in both practice and theory. An algorithm-based content retrieval in the massive data set is studied. To avoid the loss of information, the algorithm based on the Support Vector Machine classification is proposed. Also, the experiment on the real data set is made.     

两次磁暴期间广东电网地磁感应电流的分析

地磁感应电流(Geomagnetically Induced Current, GIC)会对低纬和赤道地区高压电网安全运行构成威胁.本文利用广东肇庆地磁台在2006年12月14—15日,2015年3月17日两个磁暴发生期间监测到的地磁场数据,研究和计算了广东500 kV电网两条输电线路上由地磁暴激发的GIC,并利用NASA Space Physics Data Facility网站提供的太阳风和行星际磁场数据分析了该区电离层赤道电急流(Equatorial Electrojet, EEJ).结果显示:广东500 kV电网输电线路易受地磁暴引发的GIC干扰.GIC除和输电线路的长度、线路所处的地貌特征、沿海输电线路遭受到的海岸效应有关外,赤道电急流在GIC的激发方面起着重要的作用.赤道电急流对GIC的影响发生在地磁暴的急始期,也发生于地磁暴的主相期,和行星际磁场B_z在太阳风动压增加时产生的南向偏转有关.     

Pore size distributions and hydraulic conductivities of rocks derived from Magnetic Resonance Sounding relaxation data using multi-exponential decay time inversion

In hydrogeology there is a variety of empirical formulae available for determination of hydraulic conductivity of porous media, all based on the analysis of grain size distributions of aquifer materials. Sensitivity of NMR measurements to pore sizes makes it a good indicator of hydraulic conductivity. Analogous to laboratory NMR, Magnetic Resonance Sounding (MRS) relaxation data are of a multi-exponential (ME) nature due to the distribution of different pore sizes in an investigated rock layer. ME relaxation behaviour will also arise due to the superposition of NMR signals which originate from different layers. It has been shown, that both kinds of ME behaviour coexist in MRS and can principally be separated by ME inversion of the field data. Only a few publications exist that have proposed approaches to qualitatively and quantitatively estimate petrophysical parameters such as the hydraulic conductivity from MRS measurements, i.e. MRS porosity and decay times. The so far used relations for the estimation of hydraulic conductivity in hydrogeology and NMR experiments are compared and discussed with respect to their applicability in MRS. Taking into account results from a variety of laboratory NMR and MRS experiments mean rock specific calibration factors are introduced for a data-base-calibrated estimation of hydraulic conductivity when no on-site calibration of MRS is available. Field data have been analysed using conventional and ME inversion using such mean calibration values. The results for conventional and ME inversion agree with estimates obtained from well core analysis for shallow depths but are significantly improved using a ME inversion approach for greater depths.     

南大巴山前陆褶皱带荆竹坝—石窝剖面磁组构特征及其对构造演化的制约

通过野外构造观测、岩石磁学与磁组构综合分析,本文研究了南大巴山前陆褶皱带荆竹坝—石窝剖面的叠加构造特征及其形成演化.从北东向南西,剖面构造变形总体呈减弱趋势,褶皱轴面总体倾向北东,大尺度褶皱枢纽均以小角度向北西倾伏.古应力分析显示最大主压应力为北东—南西向,反映以南大巴山的推覆为主.剖面J3之前的采样层位主要表现为变形组构,而J3-K1的采样层位则表现为初始弱变形组构.磁线理呈NW-SE向的优势方位,与剖面主构造线基本平行,主要反映来自南大巴山的推覆挤压.剖面发育特殊磁组构：①磁面理与地层面斜交,主要与褶皱作用中的平行层简单剪切相关;②磁线理均不同程度斜交于地层走向,指示构造叠加背景.沿剖面北东向南西区段Kmin的倾伏角随构造变形强度减弱而增大,据此相关性可将Kmin的倾伏角作为判别弱变形沉积岩变形强度的标志.本文认为,在晚侏罗世以南大巴山的推覆为主而米仓山短轴背斜与川东褶皱带挤压次之的联合作用使南大巴山前陆褶皱带具有构造叠加特征,之后的早白垩世仍主要表现为南大巴山的推覆,而其他两个方向的挤压较之前相对较弱.该结果也反映了秦岭J3-K1陆内造山作用及燕山期雪峰陆内构造变形的影响,为探索陆内构造与陆内造山的大陆动力学提供了佐证.