Multicentre magnetic resonance texture analysis trial using reticulated foam test objects.

Texture analysis in magnetic resonance imaging has the ability to provide useful diagnostic information with respect to the discrimination of disease states of a single tissue or the separation of different tissues. However, for widespread use it is necessary to determine how texture measurements carried out in one center relate to those carried out in another. To this end, a multicentre trial has been performed where reticulated foam test objects have been scanned in six European centers according to a fixed protocol. It has been concluded that texture measurements are not transportable between centers. Principal component models calculated from the texture parameters collected in one center do not fit the data collected in another. Further trials are to investigate whether the reticulated foam test objects may be used to normalize tissue texture data collected in different centers.     

MRI texture analysis on texture test objects, normal brain and intracranial tumors

Texture analysis was performed in three different MRI units on T1 and T2-weighted MR images from 10 healthy volunteers and 63 patients with histologically confirmed intracranial tumors. The goal of this study was a multicenter evaluation of the usefulness of this quantitative approach for the characterization of healthy and pathologic human brain tissues (white matter, gray matter, cerebrospinal fluid, tumors and edema). Each selected brain region of interest was characterized with both its mean gray level values and several texture parameters. Multivariate statistical analyses were then applied in order to discriminate each brain tissue type represented by its own set of texture parameters. Texture analysis was previously performed on test objects to evaluate the method dependence on acquisition parameters and consequently the interest of a multicenter evaluation. Even obtained on different sites with their own acquisition routine protocol, MR brain images contain textural features that can reveal discriminant factors for tissue classification and image segmentation. It can also offer additional information in case of undetermined diagnosis or to develop a more accurate tumor grading.     

基于泡沫微观渗流特征的泡沫驱数学模型

通过泡沫微观渗流实验可以看出泡沫在多孔介质内呈现两种渗流状态:流动泡沫和捕集泡沫.泡沫封堵实验可以看出泡沫封堵能力具有叠加性,当泡沫驱达到稳态后,岩心入口端泡沫封堵压力梯度小于岩心后段封堵压力梯度.基于泡沫总量平衡思想和泡沫性质表征模型,建立泡沫驱多组分数学模型.对该模型进行数值求解,模型采用全隐式方法求解.通过与泡沫封堵实验拟合,验证了模型的有效性,在此基础上研究了泡沫驱过程中不同位置处泡沫数目、压力、含水饱和度等泡沫驱渗流特征参数变化规律.     

Remyelination assessment by MRI texture analysis in a cuprizone mouse model

The purpose of this study was to perform serial texture analysis of brain MRI of cuprizone-treated mice for the assessment of regional demyelination and remyelination. Cuprizone-fed mice undergo a brain demyelination process. This process was followed over 56 days by MRI in the olfactory bulbs, cerebellum, putamen and brain stem. The texture of T2-weighted images has been analyzed at two levels: (1) with the average intensity as first order parameter and (2) with several higher order parameters for the best differentiation between myelinated (controls) and demyelinated brains. The most pertinent of these parameters, called horizontal gray level nonuniformity (HGLNU), has been selected by stepwise discriminant analysis. The time evolution of the average value of HGLNU not only confirmed the overall demyelination tendency followed by the average intensity, but also more precisely characterized a transitory remyelination on day 41 in the olfactory bulbs and cerebellum, in agreement with already published immunohistochemical destructive studies.     

Pneumatic foam generation in the presence of a high-intensity ultrasound field

Designer foams find applications in a wide range of industries. Foam quality is mostly determined by its complex cellular structure which defines its texture, rheology and stability. In addition to formulation design, the formation process is crucial to the development of a foam with an optimum structure. There is, therefore, a need for techniques that can assist in the generation of controlled foam structures. The work described in this paper demonstrates the potential of using high-intensity ultrasound to control foam structure during production. Foam generated in the presence of ultrasound usually exhibits a narrower bubble size distribution, i.e. a more uniform texture. Such enhanced homogeneity in texture is desirable to reduce the presence of aesthetically unattractive large cavities, and to reduce the destabilising effects of foam coarsening. In addition, a smaller mean bubble size and a slower rate of foam collapse usually result when ultrasound is applied. The work shows the effects on foams stabilised with different surfactants.     

A study on compressive shock wave propagation in metallic foams

Metallic foam can dissipate a large amount of energy due to its relatively long stress plateau,which makes it widely applicable in the design of structural crashworthiness. However,in some experimental studies,stress enhancement has been observed when the specimens are subjected to intense impact loads,leading to severe damage to the objects being protected. This paper studies this phenomenon on a 2D mass-spring-bar model. With the model,a constitutive relationship of metal foam and corresponding loading an...     

Diffusion tensor MRI to investigate dementias: a brief review

Diffusion tensor magnetic resonance imaging (DT-MRI) is a powerful quantitative technique with the ability to detect in vivo microscopic characteristics and abnormalities of brain tissue. It has been successfully applied to a number of neurological conditions, such as stroke, multiple sclerosis and brain tumors, providing information otherwise inaccessible on the pathological substrates. DT-MRI has also been used to study patients with cognitive decline, mainly those with Alzheimer's disease. Several image-analysis approaches have been employed, including region of interest, histogram, voxel-based analyses and DT-MRI-based tractography. Specific patterns of spatial distribution of tissue damage and correlations with neuropsychological measures have been reported. This review focuses on the use of DT-MRI to investigate dementias. The main clinical results and the different methods of image analysis will be overviewed and discussed.     

Probing spacetime foam with extragalactic sources

Because of quantum fluctuations, spacetime is probably "foamy" on very small scales. We propose to detect this texture of spacetime foam by looking for halo structures in the images of distant quasars. We find that the Very Large Telescope interferometer will be on the verge of being able to probe the fabric of spacetime when it reaches its design performance. Our method also allows us to use spacetime foam physics and physics of computation to infer the existence of dark energy or matter, independent of the evidence from recent cosmological observations.     

Analysis of the phase composition of human kidney stones in model objects with the use of synchrotron radiation diffraction

The possibility of using synchrotron radiation for X-ray diffraction analysis of kidney stones directly in a human has been investigated. Experiments using a special phantom object imitating a human body have been performed. The experimental results obtained show that the significant thickness of the objects studied and the presence of liquids and biological polymers do not impose fundamental limitations on the possibility of in vivo synchrotron radiation diffraction analysis of human kidney stones.     

Functional connectivity in the rat brain: a complex network approach

Functional connectivity analyses of fMRI data can provide a wealth of information on the brain functional organization and have been widely applied to the study of the human brain. More recently, these methods have been extended to preclinical species, thus providing a powerful translational tool. Here, we review methods and findings of functional connectivity studies in the rat. More specifically, we focus on correlation analysis of pharmacological MRI (phMRI) responses, an approach that has enabled mapping the patterns of connectivity underlying major neurotransmitter systems in vivo. We also review the use of novel statistical approaches based on a network representation of the functional connectivity and their application to the study of the rat brain functional architecture.     

A novel content-based active contour model for brain tumor segmentation

Brain tumor segmentation is a crucial step in surgical and treatment planning. Intensity-based active contour models such as gradient vector flow (GVF), magneto static active contour (MAC) and fluid vector flow (FVF) have been proposed to segment homogeneous objects/tumors in medical images. In this study, extensive experiments are done to analyze the performance of intensity-based techniques for homogeneous tumors on brain magnetic resonance (MR) images. The analysis shows that the state-of-art methods fail to segment homogeneous tumors against similar background or when these tumors show partial diversity toward the background. They also have preconvergence problem in case of false edges/saddle points. However, the presence of weak edges and diffused edges (due to edema around the tumor) leads to oversegmentation by intensity-based techniques. Therefore, the proposed method content-based active contour (CBAC) uses both intensity and texture information present within the active contour to overcome above-stated problems capturing large range in an image. It also proposes a novel use of Gray-Level Co-occurrence Matrix to define texture space for tumor segmentation. The effectiveness of this method is tested on two different real data sets (55 patients - more than 600 images) containing five different types of homogeneous, heterogeneous, diffused tumors and synthetic images (non-MR benchmark images). Remarkable results are obtained in segmenting homogeneous tumors of uniform intensity, complex content heterogeneous, diffused tumors on MR images (T1-weighted, postcontrast T1-weighted and T2-weighted) and synthetic images (non-MR benchmark images of varying intensity, texture, noise content and false edges). Further, tumor volume is efficiently extracted from 2-dimensional slices and is named as 2.5-dimensional segmentation.     

Texture analysis of brain MRI evidences the amygdala activation by nociceptive stimuli under deep anesthesia in the propofol-formalin rat model

Magnetic resonance images of rat brain were analyzed by texture analysis in order to study the effects of a nociceptive stimulation (formalin test) under propofol deep anesthesia. Changes of the texture in different cerebral brain areas acquired before and after stimulation were checked. Our statistical analysis of texture shows that these changes were present only in the amygdala, in agreement with the facts already known about the unconscious memorization of nociceptive stimuli.     

New method development in prehistoric stone tool research: Evaluating use duration and data analysis protocols

Lithic microwear is a research field of prehistoric stone tool (lithic) analysis that has been developed with the aim to identify how stone tools were used. It has been shown that laser scanning confocal microscopy has the potential to be a useful quantitative tool in the study of prehistoric stone tool function. In this paper, two important lines of inquiry are investigated: (1) whether the texture of worn surfaces is constant under varying durations of tool use, and (2) the development of rapid objective data analysis protocols. This study reports on the attempt to further develop these areas of study and results in a better understanding of the complexities underlying the development of flexible analytical algorithms for surface analysis. The results show that when sampling is optimised, surface texture may be linked to contact material type, independent of use duration. Further research is needed to validate this finding and test an expanded range of contact materials. The use of automated analytical protocols has shown promise but is only reliable if sampling location and scale are defined. Results suggest that the sampling protocol reports on the degree of worn surface invasiveness, complicating the ability to investigate duration related textural characterisation.     

Evaluation of discrete orthogonal versus polar Stockwell Transform for local multi-resolution texture analysis using brain MRI of multiple sclerosis patients

The Stockwell Transform has the potential to perform multi-resolution texture analysis in magnetic resonance imaging (MRI). However, it is computationally intensive and memory demanding. The polar Stockwell Transform (PST) is rotation-invariant and relatively memory efficient, but still computationally demanding. The new Discrete Orthogonal Stockwell Transform (DOST) appears to have addressed both the computation and storage challenges; however, its utility in localized texture analysis remains unclear. Our goal was to investigate the theory and texture analysis ability of the DOST versus PST using both synthetic and MR images, and explore the relative importance of the associated texture features using a simple classification example based on clinical brain MRI of six multiple sclerosis patients. MRI texture analysis focused on FLAIR images, and the classification used a machine learning algorithm, random forest, that differentiated regions of interest (ROIs) into 2 classes: white matter lesions, and the contralateral normal-appearing white matter (control). Our results showed that the PST features had a greater ability in detecting subtle changes in image structure than the DOST and polar-index DOST (PDOST). Quantitatively, based on 187 lesion and 187 control ROIs, both the PST and the rotation-invariant radial PST performed better in the classification than the DOST and PDOST, where the latter were no better than guessing (p = 0.65 and 0.98). Further analysis using a hierarchical random forest showed that combining MRI signal intensity with the PST or DOST predictions increased the classification performance, with the accuracy, sensitivity, and specificity all improved to >85% in the tests. Collectively, the DOST is less competitive than the PST in localized image texture analysis. The PST features may help with texture-based lesion classification in MS based on clinical brain MRI scans following further verification.     

X射线相衬成像法在线表征冷冻靶技术

阐述了冷冻靶类球面物体X射线相衬成像机理;Tracepro软件模拟研究证明了X射线相衬成像法能用于冷冻靶燃料层参数的表征;研制了在线表征冷冻靶的X射线相衬成像实验装置,利用该装置开展了二乙烯基苯泡沫球壳及实际氘氘冷冻靶的X射线相衬成像实验研究,获得了玻璃微球内氘氘冷冻层X射线相衬图像,成像分辨力达1.5 m;利用X射线相衬成像法可同时表征烧蚀球壳及冷冻燃料层,为惯性约束聚变实验提供冷冻靶参数。     

Three dimensional texture analysis in MRI: a preliminary evaluation in gliomas

The discrimination of tumor boundaries from normal tissue, as well as the evaluation of tissue heterogeneity and tumor grading often continue to pose a challenge in MRI. Although yielding promising results in various fields of medical imaging, two- dimensional (2D) texture analysis in MRI has, until now, demonstrated a lack of specificity in brain tumor classification. A new three-dimensional (3D) approach using Cooccurrence Matrix analysis is proposed to increase the sensitivity and specificity of brain tumor characterization. A preliminary comparative evaluation of 2D and 3D texture analysis was performed on T(1)-weighted MRI of seven gliomas for characterization of solid tumor, necrosis, edema and surrounding white matter. With 3D compared to 2D method, a better discrimination is obtained between necrosis and solid tumor as well as between edema and solid tumor. Using both methods, peritumoral white matter overlaps with edema, but is completely separated from far homo-lateral matter. This latter shows a complete overlapping with contra-lateral matter. The 3D texture analysis approach could provide a new tool for tumor grading and treatment follow-up, as well as for surgery or radiation therapy planning.     

基于微透镜阵列的实时三维物体识别

提出一种基于微透镜阵列多视角成像特点,将三维物体的深度信息转化为二维透射像阵列的角度信息,利用光学二维图像识别技术,实现对三维物体识别的方法.对识别过程进行了理论分析和计算,用匹配滤波的方法实现了对三维物体骰子的实时识别.实验结果表明,本方法的相关识别能力较高,并且具有很强的灵活性,对于有微小旋转、微小平移的三维物体也可进行识别.     

制备低密度聚-4-甲基-1-戊烯泡沫中的热性能研究

 在聚-4-甲基-1-戊烯(pmp)低密度泡沫的制备中,利用示差扫描量热（DSC）分析仪对pmp聚合物在均四甲苯/萘所组成的溶剂/非溶剂二元体系中的凝胶化过程进行在线测量。测定了它的凝胶化范围以及凝胶化温度与冷却速率和pmp在溶剂/非溶剂体系中所占比例的关系。利用热重-示差扫描量热（TG-DSC）系统对所制备的低密度pmp泡沫的热性能进行了分析,得到了泡沫密度变化对热稳定性等的影响。     

Vibration mode analysis using electronic speckle pattern interferometry

The use of electronic speckle pattern interferometry as a non-destructive testing technique has been widely reported for measuring a variety of objects. When used for vibration mode analysis, the only information presented to the operator was at the nodal area. The instrument has been developed so that, with the use of a microcomputer, the operator can now produce an isometric view of an object vibrating in a resonant mode, making the results easier to interpret. The instrument provides a real-time, non-contact alternative to other mode analysis equipment and can detect high-order modes as easily as low-order modes.     

The neutron texture diffractometer at the China Advanced Research Reactor

The first neutron texture diffractometer in China has been built at the China Advanced Research Reactor,due to strong demand for texture measurement with neutrons from the domestic user community. This neutron texture diffractometer has high neutron intensity, moderate resolution and is mainly applied to study texture in commonly used industrial materials and engineering components. In this paper, the design and characteristics of this instrument are described. The results for calibration with neutrons and quantitative texture analysis of zirconium alloy plate are presented. The comparison of texture measurements with the results obtained in HIPPO at LANSCE and Kowari at ANSTO illustrates the reliability of the texture diffractometer.