Knowledge-based 3D analysis from 2D medical images

An anatomical knowledge-based system for image analysis that interprets CT/MR (computed tomography/magnetic resonance) images of the human chest cavity is reported. The approach utilizes a low-level image analysis system with the ability to analyze the data in bottom-up (or data-driven) and top-down (or model-driven) modes to improve the high-level recognition process. Several image segmentation algorithms, including K-means clustering, pyramid-based region extraction, and rule-based merging, are used for obtaining the segmented regions. To obtain a reasonable number of well-segmented regions that have a good correlation with the anatomy, a priori knowledge in the form of masks is used to guide the segmentation process. Segmentation of the brain is also considered.     

Whole-brain 3D MR fingerprinting brain imaging: clinical validation and feasibility to patients with meningioma

Magnetic Resonance Materials in Physics, Biology and Medicine - MR fingerprinting (MRF) is a MR technique that allows assessment of tissue relaxation times. The purpose of this study is to evaluate...     

Comparison of 2D and 3D quiescent-interval slice-selective non-contrast MR angiography in patients with peripheral artery disease

Magnetic Resonance Materials in Physics, Biology and Medicine - To evaluate the potential clinical benefit of the superior spatial resolution of 3D prototype thin-slab stack-of-stars (tsSOS)...     

二维／三维场域有限元分析的可视化前后处理方法

介绍了二维／三维多种介质、多连通域任意形状有限元剖分的前处理方法及二维／三维结果数据的表示、等位图、向量图和数据取样的曲线的绘制方法,并给出了一个三维耦合场问题的计算实例。     

MR T2-weighted image of subacute cerebral infarct can be isointense to the surrounding brain: MR fogging in cerebral infarct

Cerebral infarcts initially showing as markedly hyperintense on magnetic resonance (MR)T ₂-weighted images decreased in intensity and became nearly isointense to normal brain tissue in subsequent MR studies. This MR fogging was observed in 7 (23%) out of 31 cases of cortical infarct and 4 (20%) out of 20 cases of perforator infarct in the second to sixth weeks of the disease. In all fogging cases, significant contrast enhancement (CE) was seen in the fogging area after intravenous administration of MR contrast agent. The CE study is recommended in MR of cerebral infarct during the subacute and early chronic stage.     

3D reconstruction of skin surface from photometric stereo images with specular reflection and interreflection

This paper describes a new method for reconstructing the structure of a skin surface replica from three shading images taken from three different lightings. Since the shading images include specular reflections and interreflection, the conventional photometric stereo method is not suitable for reconstructing its surface structure. In the proposed method, the evaluation function of the surface shape is defined, then the structure is reconstructed by optimizing the evaluation using simulated annealing. The experimental results from both synthetic images and real images demonstrate that the proposed method is more effective for shape reconstruction from shading images which include specular reflection and interreflection. © 1999 Scripta Technica, Electr Eng Jpn, 129(3): 51–58, 1999     

Accuracy of 3D MR microscopy for trabecular bone assessment: a comparative study on calcaneus samples using 3D synchrotron radiation microtomography

Magnetic resonance (MR) imaging is attractive for a noninvasive and radiation-free assessment of in vivo trabecular bone architecture. However the quantitative evaluation of architectural parameters could be biased by the limited sensitivity of MR. The aim of this study was to determine the accuracy of trabecular bone architectural parameters obtained from 3D high-resolution MR images, by comparison to reference images obtained by high-resolution X-ray microtomography using synchrotron radiation, from 29 samples of human calcaneus. MR images were obtained with a 66 m×66 m×66 m voxel size, using a 8.5 T MR microscope. Microtomography images were acquired with a 10 m×10 m×10 m voxel size, from the same samples. 3D architectural parameters characterizing the morphometry, topology, anisotropy, and orientation were computed from both modalities and carefully compared. To avoid errors, an identical region of interest was selected in the two corresponding images, and the same algorithms were run at identical spatial resolution. Our results establish that network connectivity, orientation and anisotropy are reliable from the MR data. The bone volume fraction, and morphometric parameters measured from the MR data, were found to be biased with respect to their values from the microtomography data, although there was a significant correlation between the two modalities.An erratum to this article can be found at     

Automated segmentation and volumetric analysis of renal cortex,medulla, and pelvis based on non-contrast-enhanced T1- and T2-weighted MR images

Object

The aim of our study was to enable automatic volumetry of the entire kidneys as well as their internal structures (cortex, medulla, and pelvis) from native magnetic resonance imaging (MRI) data sets.

Materials and methods

Segmentation of the entire kidneys and differentiation of their internal structures were performed in 12 healthy volunteers based on non-contrast-enhanced T1- and T2-weighted MR images. Two data sets (each acquired in one breath-hold) were co-registered using a rigid registration algorithm compensating for possible breathing-related displacements. An automatic algorithm based on thresholding and shape detection segmented the kidneys into their compartments and was compared to a manual labeling procedure.

Results

The resulting kidney volumes of the automated segmentation correlated well with those created manually (R ² = 0.96). Average volume errors were determined to be 4.97 ± 4.08 % (entire kidney parenchyma), 7.03 ± 5.56 % (cortex), 12.33 ± 7.35 % (medulla), and 17.57 ± 14.47 % (pelvis). The variation of the kidney volume resulting from the automatic algorithm was found to be 4.76 % based on the measuring of one volunteer with three independent examinations.

Conclusion

The results demonstrate the feasibility of an accurate and repeatable automatic segmentation of the kidneys and their internal structures from non-contrast-enhanced magnetic resonance images.     

Fast reduction of undersampling artifacts in radial MR angiography with 3D total variation on graphics hardware

Objective  

Subsampling of radially encoded MRI acquisitions in combination with sparsity promoting methods opened a door to significantly increased imaging speed, which is crucial for many important clinical applications. In particular, it has been shown recently that total variation (TV) regularization efficiently reduces undersampling artifacts. The drawback of the method is the long reconstruction time which makes it impossible to use in daily clinical practice, especially if the TV optimization problem has to be solved repeatedly to select a proper regularization parameter.     

Automatic gallbladder segmentation using combined 2D and 3D shape features to perform volumetric analysis in native and secretin-enhanced MRCP sequences

Objectives

We aimed to develop the first fully automated 3D gallbladder segmentation approach to perform volumetric analysis in volume data of magnetic resonance (MR) cholangiopancreatography (MRCP) sequences. Volumetric gallbladder analysis is performed for non-contrast-enhanced and secretin-enhanced MRCP sequences.

Materials and methods

Native and secretin-enhanced MRCP volume data were produced with a 1.5-T MR system. Images of coronal maximum intensity projections (MIP) are used to automatically compute 2D characteristic shape features of the gallbladder in the MIP images. A gallbladder shape space is generated to derive 3D gallbladder shape features, which are then combined with 2D gallbladder shape features in a support vector machine approach to detect gallbladder regions in MRCP volume data. A region-based level set approach is used for fine segmentation. Volumetric analysis is performed for both sequences to calculate gallbladder volume differences between both sequences.

Results

The approach presented achieves segmentation results with mean Dice coefficients of 0.917 in non-contrast-enhanced sequences and 0.904 in secretin-enhanced sequences.

Conclusion

This is the first approach developed to detect and segment gallbladders in MR-based volume data automatically in both sequences. It can be used to perform gallbladder volume determination in epidemiological studies and to detect abnormal gallbladder volumes or shapes. The positive volume differences between both sequences may indicate the quantity of the pancreatobiliary reflux.

     

纳米结构Sb2Te3的合成与分析

介绍了在开放和封闭两种状态下采用水热合成方法制备纳米结构Sb2Te3材料,并对不同反应温度、反应条件的样品进行测试分析,包括X射线衍射光谱法(XRD)、透射电子显微镜法(TEM)以及粒度分布等.实验结果表明.不同的合成工艺条件所获得产物均为Sb2Te3,但其反应进行的程度、尺寸大小以及形貌都不尽相同.获得的Sb2Te3纳米颗粒的直径最大不超过140 nm.     

Influence of principal component analysis acceleration factor on velocity measurement in 2D and 4D PC-MRI

Objective

The objective of the study was to determine how to optimize 2D and 4D phase-contrast magnetic resonance imaging (PC-MRI) acquisitions to acquire flow velocities in millimetric vessels. In particular, we search for the best compromise between acquisition time and accuracy and assess the influence of the principal component analysis (PCA).

Materials and methods

2D and 4D PC-MRI measurements are conducted within two in vitro vessel phantoms: a Y-bifurcation phantom, the branches of which range from 2 to 5 mm in diameter, and a physiological subject-specific phantom of the carotid bifurcation. The same sequences are applied in vivo in carotid vasculature.

Results

For a vessel oriented in the axial direction, both 2D and axial 4D PC-MRI provided accuracy measurements regardless of the k-t PCA factor, while the acquisition time is reduced by a factor 6 for k-t PCA maximum value. The in vivo measurements show that the proposed sequences are adequate to acquire 2D and 4D velocity fields in millimetric vessels and with clinically realistic time durations.

Conclusion

The study shows the feasibility of conducting fast, high-resolution PC-MRI flow measurements in millimetric vessels and that it is worth maximizing the k-t PCA factor to reduce the acquisition time in the case of 2D and 4D axial acquisitions.

     

潜油电机整体三维温度场耦合计算与分析

为了研究井下工作的潜油电机各个部件温度分布情况,考虑潜油电机特殊的结构建立了包括电机定转子、扶正轴承、隔磁段、轴向范围内的气隙间润滑油、机壳以及机壳外流动原油在内的整体三维模型,依据数值传热学及流体力学相关理论,根据电磁计算求解得出YQY-143系列40kW电机的热源,采用有限体积方法利用耦合传热边界条件求解该电机的三维稳态温度场,得到电机整体的温度分布云图,并分别提取电机各部分最高温度。将计算结果与利用有限元方法所得计算结果进行对比分析,对比结果表明两种方法计算所得电机各部分温度相一致,证明计算方法及结果准确性。电机各部分最高温度值符合该系列电机绝缘等级的要求。     

碲化铋温差发电组件的寿命试验及其分析

通过寿命试验研究了TEG1-127-1.4-1.6-250型碲化铋材料温差发电组件在模拟使用过程中电输出性能的衰减规律,并讨论了碲化铋材料制备工艺对温差发电组件可靠性的影响.研究表明,在热面温度250℃,2250 h的寿命试验中,碲化铋材料温差发电组件的电输出性能衰减速率随时间的增加不断减小.热压制备碲化铋材料发电组件...     

磁性材料三维磁特性传感信号检测技术中关键问题的研究与分析

精确模拟磁性材料实际工作状态下的磁特性对于提高电机、电力变压器等电工设备的性能和效率具有重要意义。为了全面解析磁材料磁特性,提出了三维磁特性测试方法,并针对三维磁特性传感信号的检测问题进行了深入研究。设计了新型三维B-H传感线圈与传感箱并分析了三维传感线圈的校准标定等难点问题,讨论了测试过程LabVIEW运算中在三维激励条件下的积分漂移和采集中的杂波干扰等关键性问题,并提出解决方案。实验证明,所提出的解决方案是有效的,具有可行性。     

中型高压异步电动机三维温度场耦合计算与分析

电机的温升和通风沟内流体的研究对电机高效、安全和稳定运行有着重要的影响,根据流体力学和传热学理论,给出求解传热问题的能量方程.以YKK400-6(690kW)中型高压异步电机为例,分别建立电机转子、定子的三维数学模型和物理模型,给出相应的基本假设和边界条件.采用有限体积法对流体场和温度场控制方程进行耦合求解,计算出了高...     

Asymptotic stability of large-scale systems with application to power systems. Part 2: transient analysis

Based on the general decomposition-aggregation method, a transient stability analysis of power systems is explained. With respect to previous related studies, the proposed improvements are twofold. From a purely theoretical viewpoint, advantage is taken of the relaxation of the stability conditions obtained in the first part of the paper, of the choice of well adapted comparison functions, and of the definition of asymptotic stability domain estimates. From the power systems point of view, use is made of more refined mathematical models than usual; thus, in addition to transfer conductances and electromechanical damping, electromagnetic damping and governor's action are taken into account. A simple numerical example is used for illustrative purposes.     

2D time-domain electromagnetic macroscopic numerical modelling on parallel computer: application to the mm-wave silicon DIMPATT diode

A new time-domain two-dimensional (2D) electromagnetic (EM) physical modelling of non-linear distributed semiconductor devices has been developed. It is based on a numerical procedure which solves in a self consistent manner both Maxwell’s equations and a macroscopic transport model based on the drift-diffusion approximation. The software can be run on a parallel computer. It is based on finite-difference time-domain (FDTD) explicit schemes associated to the domain decomposition method. The millimetre-wave travelling-wave IMPATT diode or Distributed IMPact ionisation and Avalanche and Transit Time (DIMPATT) diode is the non linear test structure chosen to validate the model. RF simulations under amplification and CW oscillation operating modes have been performed. The results presented in this paper consist on the one hand of results that can be qualitatively compared to previously published theoretical works and on the other hand of features especially pointed out thanks to the new electromagnetic physical model capabilities.     

采用三维粘性流进行长短叶片转轮水力性能分析

在高水头领域，长短叶片混流式水轮机转轮由于其稳定性和空化性能优良而得到了广泛的应用。本文结合某项目，采用平均化N—S方程，计算水轮机内部的速度场、压力场及转轮数值效率，应用数值分析的方法对转轮性能进行预估，设计了一个长短叶片混流式水轮机转轮，并与常规转轮进行了同台试验比较。     

Spatial representation and retrieval. Getting an edge on what ittakes to find matching pairs in 3D

Discusses two functions for retrieving 3D images from large collections. One proposed representation is referred to as the 3D spatial orientation graph (SOG). SOG is a fully-connected, undirected, weighted graph. The time complexity of this SOG-based spatial similarity (SIM_3D) algorithm is Θ(|E_q|+|E_d|), where |E_q| and |E _d| are the number of edges, respectively, in the query or database images. The other proposed representation is referred to as the 3D surface normal list (SNL). The surface normal is the unit vector perpendicular to the plane formed by three space objects. A list with surface normals is used to represent an image. This SNL-based SIM_3D algorithm has linear time complexity based on the total number of objects in the query and the database images. We expect both the SOG- and SNL-based SIM_3D algorithms to be quite useful in multimedia retrieval applications such as architectural design, interior design and real-estate marketing. The original SOG algorithm has been improved to recognize rotational variant images and arbitrary variants involving a composition of translation, scaling and rotation. For the SNL algorithm, the choice of the base point is significant. It cannot recognize the difference between objects unevenly scaled along the line to the base point of an image. To overcome these limitations, an improved SNL algorithm was worked on. The improved algorithm is very robust, but it has Θ(n²) time complexity. It is effective when used for a small database or for refining the search result of the original SNL algorithm