共查询到20条相似文献,搜索用时 15 毫秒
1.
提升方法是计算离散小波变换的有效手段,将提升三维小波变换用于视频信号压缩。时间方向小渡变换选用Haar滤波器组,空间小波变换则在常规的图像编码所常用的D9/7滤波器组基础上,对其参数进行调整,进一步减少运算量。实验表明这种调整取得了与D9/7双正交小波基本一致图像编码效果,但提高了运算速度。 相似文献
2.
A comparative atomic force microscopy study on living skin fibroblasts and liver endothelial cells 总被引:7,自引:0,他引:7
Braet F de Zanger R Seynaeve C Baekeland M Wisse E 《Journal of electron microscopy》2001,50(4):283-290
Atomic force microscopy (AFM) has been used to image a wide variety of cells and has proven to be successful in cellular imaging, by comparing results obtained by AFM with SEM or TEM. The aim of the present study was to investigate further the conditions for AFM imaging of living cells and compare the results with those obtained by SEM. We chose to image skin fibroblast and liver sinusoidal endothelial cells of two different sources, because these cells have been well described and characterized in earlier studies. AFM imaging of living cells mainly reveals submembranous structures, which could not be observed by SEM. This concerns the visualization of the overall cytoskeletal architecture and organelles, without the necessity of any preparative steps. The AFM study of living cells allows a time lapse study of dynamic changes of the actin cytoskeleton under the influence of the cytoskeleton-disturbing drug cytochalasin B in cells that can be followed individually during the process. However, softer samples, such as the fenestrated parts of living rat liver sinusoidal endothelial cells in culture could not be visualized. Apparently, these cell parts are disrupted due to tip-sample interaction in contact mode. To avoid the lateral forces and smearing artefacts of contact mode AFM, non-contact imaging was applied, resulting in images of higher quality. Still, endothelial fenestrae could not be visualized. In contrast, contact imaging of immortomouse liver sinusoidal endothelial cells, which are devoid of fenestrae, could easily be performed and revealed a detailed filamentous cytoskeleton. 相似文献
3.
4.
《IEEE transactions on medical imaging》2009,28(7):1051-1061
5.
Rmili H. Mrabet O.E. Floc'h J.-M. Miane J.-L. 《Antennas and Propagation, IEEE Transactions on》2007,55(4):1045-1050
A 3-D fractal-tree monopole antenna was realized using electrochemical deposition technique. Experimental results on the return loss over the band 1-20 GHz and radiation patterns at all resonating frequencies were presented. The multiband electromagnetic behavior of the antenna was studied and compared to a previously reported 2-D fractal-tree antenna studied by C. Puente It is shown that the impedance bandwidth of the 3-D structure were improved compared to the reported 2-D structure with less dense band distribution. The resonating bands of the fractal structure are related to the length distribution over the fractal shape. Results for the 3-D fractal-tree antenna structure show the expected self-similar behavior 相似文献
6.
3-D Kalman filter for image motion estimation 总被引:1,自引:0,他引:1
This paper presents a new three-dimensional (3-D) Markov model for motion vector fields. The three dimensions consist of the two space dimensions plus a scale dimension. We use a compound signal model to handle motion discontinuity in this 3-D Markov random field (MRF). For motion estimation, we use an extended Kalman filter as a pel-recursive estimator. Since a single observation can be sensitive to local image characteristics, especially when the model is not accurate, we employ windowed multiple observations at each pixel to increase accuracy. These multiple observations employ different weighting values for each observation, since the uncertainty in each observation is different. Finally, we compare this 3-D model with earlier proposed one-dimensional (1-D) (coarse-to-fine scale) and two-dimensional (2D) spatial compound models, in terms of motion estimation performance on a synthetic and a real image sequence. 相似文献
7.
Arjuna Madanayake H.L.P. Bruton L.T. 《IEEE transactions on circuits and systems. I, Regular papers》2008,55(6):1546-1559
8.
A planar encoding of three-dimensional (3-D) images, which is commutative with respect to set and gray-scale morphological operations, is proposed. Such an encoding indicates a way to reduce 3-D set and mathematical morphology operations to two-dimensional (2-D) ones 相似文献
9.
3-D segmentation of MR images of the head for 3-D display 总被引:7,自引:0,他引:7
Algorithms for 3-D segmentation and reconstruction of anatomical surfaces from magnetic resonance imaging (MRI) data are presented. The 3-D extension of the Marr-Hildreth operator is described, and it is shown that its zero crossings are related to anatomical surfaces. For an improved surface definition, morphological filters-dilation and erosion-are applied. From these contours, 3-D reconstructions of skin, bone, brain, and the ventricular system can be generated. Results obtained with different segmentation parameters and surface rendering methods are presented. The fidelity of the generated images comes close to anatomical reality. It is noted that both the convolution and the morphological filtering are computationally expensive, and thus take a long time on a general-purpose computer. Another problem is assigning labels to the constituents of the head; in the current implementation, this is done interactively. 相似文献
10.
Registration of real-time 3-D ultrasound images of the heart for novel 3-D stress echocardiography 总被引:2,自引:0,他引:2
Shekhar R Zagrodsky V Garcia MJ Thomas JD 《IEEE transactions on medical imaging》2004,23(9):1141-1149
Stress echocardiography is a routinely used clinical procedure to diagnose cardiac dysfunction by comparing wall motion information in prestress and poststress ultrasound images. Incomplete data, complicated imaging protocols and misaligned prestress and poststress views, however, are known limitations of conventional stress echocardiography. We discuss how the first two limitations are overcome via the use of real-time three-dimensional (3-D) ultrasound imaging, an emerging modality, and have called the new procedure "3-D stress echocardiography." We also show that the problem of misaligned views can be solved by registration of prestress and poststress 3-D image sequences. Such images are misaligned because of variations in placing the ultrasound transducer and stress-induced anatomical changes. We have developed a technique to temporally align 3-D images of the two sequences first and then to spatially register them to rectify probe placement error while preserving the stress-induced changes. The 3-D spatial registration is mutual information-based. Image registration used in conjunction with 3-D stress echocardiography can potentially improve the diagnostic accuracy of stress testing. 相似文献
11.
Woodhead I.M. Buchan G.D. Kulasiri D. 《Antennas and Propagation, IEEE Transactions on》2001,49(8):1117-1122
Numerous applications of dielectric modeling require computation of the distribution of the total electric field in an inhomogeneous dielectric, in response to an applied electric field. An integral equation method would normally use an electric field volume integral technique using the moment method and hence compute the field in three-dimensional (3-D) space. For those instances where the third dimension of the region is assumed to be invariant, such as when determining the spatial sensitivity of a time-domain reflectometry sensor, the heavy resource use of calculating the additional dimension is an unnecessary burden. The new method reported in this paper sums the field contributions from the invariant third dimension at each stage of a two-dimensional (2-D) calculation, reducing the order of the model matrix by 2n2 where n is the number of cells in each dimension. Thus, by accepting a small loss in accuracy of less than 3%, this procedure reduces the required memory resource by more than 2n2,and execution time is dramatically improved. Assuming an essentially lossless permittivity, we use the calculated electric field distribution from a parallel transmission line to calculate the line's propagation velocity and demonstrate favorable comparison with measured values. Moisture content measurement is used as an example 相似文献
12.
Zagrodsky V Walimbe V Castro-Pareja CR Qin JX Song JM Shekhar R 《IEEE transactions on medical imaging》2005,24(9):1089-1099
Real-time three-dimensional (3-D) echocardiography is a new imaging modality that presents the unique opportunity to visualize the complex 3-D shape and motion of the left ventricle (LV) in vivo and to measure the associated global and local function parameters. To take advantage of this opportunity in routine clinical practice, automatic segmentation of the LV in the 3-D echocardiographic data, usually hundreds of megabytes large, is essential. We report a new segmentation algorithm for this task. Our algorithm has two distinct stages, initialization of a deformable model and its refinement, which are connected by a dual "voxel + wiremesh" template. In the first stage, mutual-information-based registration of the voxel template with the image to be segmented helps initialize the wiremesh template. In the second stage, the wiremesh is refined iteratively under the influence of external and internal forces. The internal forces have been customized to preserve the nonsymmetric shape of the wiremesh template in the absence of external forces, defined using the gradient vector flow approach. The algorithm was validated against expert-defined segmentation and demonstrated acceptable accuracy. Our segmentation algorithm is fully automatic and has the potential to be used clinically together with real-time 3-D echocardiography for improved cardiovascular disease diagnosis. 相似文献
13.
Ioannis Savidis Syed M. Alam Scott Pozder Ritwik Chatterjee 《Microelectronics Journal》2010,41(1):9-16
The integration of chips in the third dimension has been explored to address various physical and system level limitations currently undermining chip performance. In this paper, we present a comprehensive analysis of the electrical properties of through silicon vias and microconnects with an emphasis on single via characteristics as well as inter-TSV capacitive and inductive coupling in the presence of either a neighboring ground tap or a grounded substrate back plane. We also analyze the impact of technology scaling on TSV electrical parasitics, and investigate the power and delay trend in 3-D interstratum IO drivers with those of global wire in 2-D circuits over various technology nodes. We estimate the global wire length necessary to produce an equivalent 3-D IO delay, a metric useful in early stage design tools for 3D floorplanning that considers the electrical characteristics of 3D connections with TSVs and microconnects. 相似文献
14.
B. G. Mertzios A. N. Venetsanopoulos 《Multidimensional Systems and Signal Processing》1997,8(3):335-349
In this paper a fast implementation architecture of three-dimensional (3-D) FIR or IIR digital filters via systolic VLSI array processors is described. The modular structure presented is comprised of similar processing elements in a linear cascade configuration with local interconnections. High speed throughput rates are attained due to high concurrency, which is achieved by exploiting both pipelining and parallelism. The considered 3-D FIR and IIR filters may be used for the processing of reconstructed 3-D images and in medical imaging applications. 相似文献
15.
《Geoscience and Remote Sensing, IEEE Transactions on》2009,47(11):3656-3663
16.
In this paper, the morphological skeleton interpolation (MSI) algorithm is presented. It is an efficient, shape-based interpolation method used for interpolating slices in a three-dimensional (3-D) binary object. It is based on morphological skeletonization, which is used for two-dimensional (2-D) slice representation. The proposed morphological skeleton matching process provides translation, rotation, and scaling information at the same time. The interpolated slices preserve the shape of the original object slices, when the slices have similar shapes. It can also modify the shape of an object when the successive slices do not have similar shapes. Applications on artificial and real data are also presented. 相似文献
17.
随着密集波分复用[Density Wavelength Division Multiplexing(DWDM)]技术的迅速发展,在高速光传送网中,光交换设备逐渐成为限制网络通信速度的瓶颈,而基于微电子机械系统[Micro-Electro-Mechanical Systems(MEMS)]技术的光交叉连接设备被认为是未来高速光网络中节点设备的首选.本文对MEMS的光交叉连接结构进行了介绍,并对三维MEMS的光交叉连接结构的部分性能进行了研究和分析,最后讨论了基于三维MEMS结构的光分插复用器在全光通信网中的应用. 相似文献
18.
根据室内建筑行业特有的视图表示规则,提出了一种基于理解的室内建筑物三维重建方法。该方法结合室内建筑制图规则、图形识别理解技术和人工智能知识,通过基于特征抽取的识别算法,完成对室内建筑结构图中墙体中线的提取,进而获得整个建筑物墙体的拓扑结构;然后对室内建筑结构图中2种重要的建筑构件:门和窗户进行辨识;最后实现室内建筑物的三维重建。实验结果表明,在少量人机交互的基础上,该方法对实际的建筑图是十分有效的。 相似文献
19.
Pajevic S. Daube-Witherspoon M.E. Bacharach S.L. Carson R.E. 《IEEE transactions on medical imaging》1998,17(1):9-23
The authors analyzed the noise characteristics of two-dimensional (2-D) and three-dimensional (3-D) images obtained from the GE Advance positron emission tomography (PET) scanner. Three phantoms were used: a uniform 20-cm phantom, a 3-D Hoffman brain phantom, and a chest phantom with heart and lung inserts. Using gated acquisition, the authors acquired 20 statistically equivalent scans of each phantom in 2-D and 3-D modes at several activity levels. From these data, they calculated pixel normalized standard deviations (NSD's), scaled to phantom mean, across the replicate scans, which allowed them to characterize the radial and axial distributions of pixel noise. The authors also performed sequential measurements of the phantoms in 2-D and 3-D modes to measure noise (from interpixel standard deviations) as a function of activity. To compensate for the difference in axial slice width between 2-D and 3-D images (due to the septa and reconstruction effects), they developed a smoothing kernel to apply to the 2-D data. After matching the resolution, the ratio of image-derived NSD values (NSD2D/NSD3D)2 averaged throughout the uniform phantom was in good agreement with the noise equivalent count (NEC) ratio (NEC3D/NEC2D). By comparing different phantoms, the authors showed that the attenuation and emission distributions influence the spatial noise distribution. The estimates of pixel noise for 2-D and 3-D images produced here can be applied in the weighting of PET kinetic data and may be useful in the design of optimal dose and scanning requirements for PET studies. The accuracy of these phantom-based noise formulas should be validated for any given imaging situation, particularly in 3-D, if there is significant activity outside the scanner field of view 相似文献
20.
Recent advances in programming languages for graphics processing units (GPUs) provide developers with a convenient way of implementing applications which can be executed on the CPU and GPU interchangeably. GPUs are becoming relatively cheap, powerful, and widely available hardware components, which can be used to perform intensive calculations. The last decade of hardware performance developments shows that GPU-based computation is progressing significantly faster than CPU-based computation, particularly if one considers the execution of highly parallelisable algorithms. Future predictions illustrate that this trend is likely to continue. In this paper, we introduce a way of accelerating 2-D/3-D image registration by developing a hybrid system which executes on the CPU and utilizes the GPU for parallelizing the generation of digitally reconstructed radiographs (DRRs). Based on the advancements of the GPU over the CPU, it is timely to exploit the benefits of many-core GPU technology by developing algorithms for DRR generation. Although some previous work has investigated the rendering of DRRs using the GPU, this paper investigates approximations which reduce the computational overhead while still maintaining a quality consistent with that needed for 2-D/3-D registration with sufficient accuracy to be clinically acceptable in certain applications of radiation oncology. Furthermore, by comparing implementations of 2-D/3-D registration on the CPU and GPU, we investigate current performance and propose an optimal framework for PC implementations addressing the rigid registration problem. Using this framework, we are able to render DRR images from a 256×256×133 CT volume in ~?24 ms using an NVidia GeForce 8800 GTX and in ~?2 ms using NVidia GeForce GTX 580. In addition to applications requiring fast automatic patient setup, these levels of performance suggest image-guided radiation therapy at video frame rates is technically feasible using relatively low cost PC architecture. 相似文献