Visualization of 3D variable in time object based on data gathered by active measurement system

The recent needs of analysis and visualization of variable in time real 3D objects in many applications require development of new approach towards combining rapid 3D shape acquisition and the methodology of data processing in order to perform visualization and analysis of real 3D dynamic objects. In this paper, the general concept of visualization system of data gathered by means of optical 4D (x,y,z,t) shape measurement system is presented. The concept of a virtual camera, as the mean for interactive object visualization is introduced. The experimental results for processing of simulated and real variable in time 3D object are presented and discussed. The directions of future works focused on full implementation of the concept are introduced.     

3D reconstruction of road surfaces using an integrated multi-sensory approach

In this paper, we present our experience in building a mobile imaging system that incorporates multi-modality sensors for road surface mapping and inspection applications. Our proposed system leverages 3D laser-range sensors, video cameras, global positioning systems (GPS) and inertial measurement units (IMU) towards the generation of photo-realistic, geometrically accurate, geo-referenced 3D models of road surfaces. Based on our summary of the state-of-the-art systems for a road distress survey, we identify several challenges in the real-time deployment, integration and visualization of the multi-sensor data. Then, we present our data acquisition and processing algorithms as a novel two-stage automation procedure that can meet the accuracy requirements with real-time performance. We provide algorithms for 3D surface reconstruction to process the raw data and deliver detail preserving 3D models that possess accurate depth information for characterization and visualization of cracks as a significant improvement over contemporary commercial video-based vision systems.     

A spectral invariant representation of spectral reflectance

Spectral image acquisition as well as color image is affected by several illumination factors such as shading, gloss, and specular highlight. Spectral invariant representations for these factors were proposed for the standard dichromatic reflection model of inhomogeneous dielectric materials. However, these representations are inadequate for other characteristic materials like metal. This paper proposes a more general spectral invariant representation for obtaining reliable spectral reflectance images. Our invariant representation is derived from the standard dichromatic reflection model for dielectric materials and the extended dichromatic reflection model for metals. We proof that the invariant formulas for spectral images of natural objects preserve spectral information and are invariant to highlights, shading, surface geometry, and illumination intensity. It is proved that the conventional spectral invariant technique can be applied to metals in addition to dielectric objects. Experimental results show that the proposed spectral invariant representation is effective for image segmentation.     

Clinical applications of computer aided visualization

The clinical applications of computer aided three-dimensional (3D) data visualization are now numerous. In this paper, we describe the importance of visualization in clinical applications and the methods that are appropriate to particular specialisations. We discuss the requirements of some of these clinical specialisations and describe how developments have taken place over the years to meet these both in terms of new computer algorithms and hardware. We present some selected examples of major clinical applications of data visualization, and end with a note on social, legal and ethical implications.     

Data reduction by applying an image-based modeling and rendering technique to CG models

We applied an image-based modeling and rendering technique to reduce the data size of a CG model to be obtained as a visualization result. To date, this technique has been applied to the reconstruction of 3D graphical models from real objects; the size of the models can be reduced effectively because both color information and geometric information can be reduced. We applied a silhouette-and-voxel method that does not require design data for geometric simplification. Using our system, we simplified two models, one of which, involving medical data, was reduced by about 85% in file size. An accompanying subjective quality test showed that our approach maintains approximately the same visual quality as the geometric simplification method traditionally used.     

A fast 3D look-locker method for volumetric T1 mapping.

We introduce a fast technique, based on the principles of the 2D Look-Locker T1 measurement scheme, to rapidly acquire the data for accurate maps of T1 in three dimensions. The acquisition time has been shortened considerably by segmenting the acquisition of the k(y) phase encode lines. Using this technique, the data for a 256 x 128 x 32 volumetric T1 measurement can be acquired in 7.6 min. T1 measurements made in phantoms with T1s between 200 and 1200 ms had an accuracy of 4% and a reproducibility of 3.5%. Measurements of T1 made in normal brain using the fast 3D sequence corresponded well with inversion-recovery fast spin-echo measurements.     

Three-dimensional visualization of objects in scattering medium using integral imaging and spectral analysis

This paper presents a three-dimensional visualization method of 3D objects in a scattering medium. The proposed method employs integral imaging and spectral analysis to improve the visual quality of 3D images. The images observed from 3D objects in the scattering medium such as turbid water suffer from image degradation due to scattering. The main reason is that the observed image signal is very weak compared with the scattering signal. Common image enhancement techniques including histogram equalization and contrast enhancement works improperly to overcome the problem. Thus, integral imaging that enables to integrate the weak signals from multiple images was discussed to improve image quality. In this paper, we apply spectral analysis to an integral imaging system such as the computational integral imaging reconstruction. Also, we introduce a signal model with a visibility parameter to analyze the scattering signal. The proposed method based on spectral analysis efficiently estimates the original signal and it is applied to elemental images. The visibility-enhanced elemental images are then used to reconstruct 3D images using a computational integral imaging reconstruction algorithm. To evaluate the proposed method, we perform the optical experiments for 3D objects in turbid water. The experimental results indicate that the proposed method outperforms the existing methods.     

3DSEM++: Adaptive and intelligent 3D SEM surface reconstruction

Structural analysis of microscopic objects is a longstanding topic in several scientific disciplines, such as biological, mechanical, and materials sciences. The scanning electron microscope (SEM), as a promising imaging equipment has been around for decades to determine the surface properties (e.g., compositions or geometries) of specimens by achieving increased magnification, contrast, and resolution greater than one nanometer. Whereas SEM micrographs still remain two-dimensional (2D), many research and educational questions truly require knowledge and facts about their three-dimensional (3D) structures. 3D surface reconstruction from SEM images leads to remarkable understanding of microscopic surfaces, allowing informative and qualitative visualization of the samples being investigated. In this contribution, we integrate several computational technologies including machine learning, contrario methodology, and epipolar geometry to design and develop a novel and efficient method called 3DSEM++ for multi-view 3D SEM surface reconstruction in an adaptive and intelligent fashion. The experiments which have been performed on real and synthetic data assert the approach is able to reach a significant precision to both SEM extrinsic calibration and its 3D surface modeling.     

Four-dimensional geometric element definitions and interferences via five-dimensional homogeneous processing

Abstract  

We have systematized various studies on 4-D visualization and interaction thus far, and we proposed 4-D geometric algorithms via 5-D homogeneous processing. Our framework uses 5 × 5 matrices and 5 × 5 determinants to express various types of transformations, and it simplifies geometric operations without the use of division operations. Using the proposed scheme, we developed an interactive 4-D space display system. The simplicity, generality, and duality of 5-D homogeneous processing are effective not only for 4-D geometric operations but also for interference problems among various 4-D objects. However, the processing regarding geometric characteristics of 4-D objects was not considered in our previous works. In this paper, we describe 4-D geometric elements, in general, and we discuss 4-D computational geometry via 5-D homogeneous processing. Unified geometric operations without the use of division operations constitute the most important part of 5-D homogeneous processing. We systematize the methods for 4-D geometric element definitions and interferences via 5-D homogeneous processing. In the field of 4-D visualization, the proposed algorithms can be potentially used in a user interface for feature detection of a 4-D object and collision detection of several 4-D objects. We comprehensively develop and advance the theoretical framework in the field of 4-D graphics. It is expected that this method of processing will be useful for the performance improvement of 4-D graphics systems.     

A comparison of three SPRITE techniques for the quantitative 3D imaging of the 23Na spin density on a 4T whole-body machine

Sodium density maps acquired with three SPRITE-based methods have been compared in terms of the resulting quantitative information as well as image quality and acquisition times. Consideration of factors relevant for the clinical implementation of SPRITE shows that the Conical-SPRITE variant is preferred because of a 20-fold reduction in acquisition time, slightly improved image quality, and no loss of quantitative information. The acquisition of a 3D data set (32x32x16; FOV=256x256x160 mm) for the quantitative determination of sodium density is demonstrated. In vivo Conical-SPRITE 23Na images of the brain of a healthy volunteer were acquired in 30 min with a resolution of 7.5x7.5x7.5 mm and a signal-to-noise ratio of 23 in cerebrospinal fluid and 17 in brain tissue.     

Dual plane in-line digital holographic microscopy

We report a dual plane in-line digital holographic microscopy technique that exploits the method of subtraction of average intensity of the entire hologram to suppress the zero-order diffracted wave. Two interferograms are recorded at different planes to eliminate the conjugate image. The experimental results demonstrate successful reconstruction of phase objects as well as of amplitude objects. The two interferograms can be recorded simultaneously, using two CCD or CMOS sensors, in order to increase the acquisition rate. This enhanced acquisition rate, together with the improved reconstruction capability of the proposed method, may find applications in biomedical research for visualization of rapid dynamic processes at the cellular level.     

A fractal-based 2D expansion method for multi-scale volume data visualization

Abstract  

Visualization of volume data is difficult to realize and control because the most common output device is a two-dimensional (2D) display and the most common input device is a mouse, which only allows 2D operation. For example, volume rendering projects the data structure onto a 2D image plane, but this type of view-dependent method gives rise to occlusion. In addition, 2D mouse operation does not allow direct selection of three-dimensional (3D) regions or coordinates. In this article, we propose a method that expands the octree structure of volume data onto a 2D plane. The proposed method uses the self-similarity of the fractal diagram and achieves multi-scale visualization of volume data in two dimensions. With this method, we can browse the entire domain of volume data without occlusion. For greater effectiveness, we combined the proposed method and existing 3D-based methods. Since each cell has a one-to-one correspondence with squares in the Sierpinski carpet, we can assign arbitrary 3D regions or positions by selecting the corresponding squares. This provides direct access to 3D regions and coordinates by 2D mouse operation. We propose some functions for interactive visualization and discuss how to exploit the advantages and lessen the disadvantages of the proposed method.     

集成成像大纵深物体的三维形貌获取技术

为了满足现代工业所需的大纵深物体的三维形貌获取需求,解决传统结构光三维形貌获取技术纵深较小的问题, 借助集成成像这种阵列式多视点获取技术,构建了基于集成成像的大纵深物体的三维形貌获取技术。从集成成像原理出发,分析了集成成像三维物点和同名像点之间的关系,得到集成成像光学获取系统参数和三维物体纵深极限之间的关系。在此基础上,利用相机和电动平移台构建了扫描式相机集成成像三维形貌获取系统,并对纵深从600 mm到3 600 mm相对独立的2个物体构建的大纵深三维物体进行了形貌获取。光学实验结果显示,该集成成像大纵深物体三维形貌获取技术能够单次获取纵深为3 600 mm的三维物体的三维形貌,为大纵深物体的三维形貌获取提供了技术支持。     

High-resolution gadolinium-enhanced 3D MRA of the infrapopliteal arteries. Lessons for improving bolus-chase peripheral MRA

Peripheral magnetic resonance angiography (MRA) is growing in use. However, methods of performing peripheral MRA vary widely and continue to be optimized, especially for improvement in illustration of infrapopliteal arteries. The main purpose of this project was to identify imaging factors that can improve arterial visualization in the lower leg using bolus chase peripheral MRA. Eighteen healthy adults were imaged on a 1.5T MR scanner. The calf was imaged using conventional three-station bolus chase three-dimensional (3D) MRA, two dimensional (2D) time-of-flight (TOF) MRA and single-station Gadolinium (Gd)-enhanced 3D MRA. Observer comparisons of vessel visualization, signal to noise ratios (SNR), contrast to noise ratios (CNR) and spatial resolution comparisons were performed. Arterial SNR and CNR were similar for all three techniques. However, arterial visualization was dramatically improved on dedicated, arterial-phase Gd-enhanced 3D MRA compared with the multi-station bolus chase MRA and 2D TOF MRA. This improvement was related to optimization of Gd-enhanced 3D MRA parameters (fast injection rate of 2 mL/sec, high spatial resolution imaging, the use of dedicated phased array coils, elliptical centric k-space sampling and accurate arterial phase timing for image acquisition). The visualization of the infrapopliteal arteries can be substantially improved in bolus chase peripheral MRA if voxel size, contrast delivery, and central k-space data acquisition for arterial enhancement are optimized. Improvements in peripheral MRA should be directed at these parameters.     

Semiautomated quality assurance for quantitative magnetic resonance imaging.

It is now well established that MRI can be used for quantitative (as opposed to simply qualitative) measurements, and good accuracy and precision have been obtained in phantom experiments. To make routine quantitative measurements as part of a clinical scanning protocol, however, quality assurance (QA) methods particularly suited to quantification must be developed. We describe a set of QA tests using clinical protocols on test phantoms, with which we have assessed quantitative performance of our Picker 0.5-T scanner (Picker International, Cleveland, OH) over 2 years. We also describe the automated data processing methods we have developed to deal with the large amounts of data generated by these tests.     

Analysis and synthesis of multicolored objects in a single image

We present a method with which to recover the intrinsic shading and reflectance characteristics of multicolored three-dimensional objects in a single image, with which realistic new scenes can be synthesized. A color watershed algorithm, which is based on a regularized dichromatic fitting error, is proposed for robust image segmentation. For shading recovery in small regions, a weighted interpolation is employed, whereas in large regions the reflectance and shading are calculated based on the assumption of gradual shape variation. It is demonstrated that the proposed method is promising and can be applied in image simulation.     

3D reconstruction of grains in polycrystalline materials using a tessellation model with curved grain boundaries

A compact and tractable representation of the grain structure of a material is an extremely valuable tool when carrying out an empirical analysis of the material’s microstructure. Tessellations have proven to be very good choices for such representations. Most widely used tessellation models have convex cells with planar boundaries. Recently, however, a new tessellation model — called the generalised balanced power diagram (GBPD) — has been developed that is very flexible and can incorporate features such as curved boundaries and non-convexity of cells. In order to use a GBPD to describe the grain structure observed in empirical image data, the parameters of the model must be chosen appropriately. This typically involves solving a difficult optimisation problem. In this paper, we describe a method for fitting GBPDs to tomographic image data. This method uses simulated annealing to solve a suitably chosen optimisation problem. We then apply this method to both artificial data and experimental 3D electron backscatter diffraction (3D EBSD) data obtained in order to study the properties of fine-grained materials with superplastic behaviour. The 3D EBSD data required new alignment and segmentation procedures, which we also briefly describe. Our numerical experiments demonstrate the effectiveness of the simulated annealing approach (compared to heuristic fitting methods) and show that GBPDs are able to describe the structures of polycrystalline materials very well.     

Uniform distribution of projection data for improved reconstruction quality of 4D EPR imaging

In continuous wave (CW) electron paramagnetic resonance imaging (EPRI), high quality of reconstruction in a limited acquisition time is a high priority. It has been shown for the case of 3D EPRI, that a uniform distribution of the projection data generally enhances reconstruction quality. In this work, we have suggested two data acquisition techniques for which the gradient orientations are more evenly distributed over the 4D acquisition space as compared to the existing methods. The first sampling technique is based on equal solid angle partitioning of 4D space, while the second technique is based on Fekete points estimation in 4D to generate a more uniform distribution of data. After acquisition, filtered backprojection (FBP) is applied to carry out the reconstruction in a single stage. The single-stage reconstruction improves the spatial resolution by eliminating the necessity of data interpolation in multi-stage reconstructions. For the proposed data distributions, the simulations and experimental results indicate a higher fidelity to the true object configuration. Using the uniform distribution, we expect about 50% reduction in the acquisition time over the traditional method of equal linear angle acquisition.