- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2018 25th IEEE International Conference on Image Processing (ICIP) - Athens, Greece (2018.10.7-2018.10.10)] 2018 25th IEEE International Conference on Image Processing (ICIP) - An Interior Point Method for Nonnegative Sparse Signal Reconstruction
摘要： We present a primal-dual interior point method (IPM) with a novel preconditioner to solve the (cid:96)1-norm regularized least square problem for nonnegative sparse signal reconstruction. IPM is a second-order method that uses both gradient and Hessian information to compute effective search directions and achieve super-linear convergence rates. It therefore requires many fewer iterations than first-order methods such as iterative shrinkage/thresholding algorithms (ISTA) that only achieve sub-linear convergence rates. However, each iteration of IPM is more expensive than in ISTA because it needs to evaluate an inverse of a Hessian matrix to compute the Newton direction. We propose to approximate each Hessian matrix by a diagonal matrix plus a rank-one matrix. This approximation matrix is easily invertible using the Sherman-Morrison formula, and is used as a novel preconditioner in a preconditioned conjugate gradient method to compute a truncated Newton direction. We demonstrate the efficiency of our algorithm in compressive 3D volumetric image reconstruction. Numerical experiments show favorable results of our method in comparison with previous interior point based and iterative shrinkage/thresholding based algorithms.
关键词： nonnegative sparse,3d volumetric image reconstruction,primal-dual preconditioned interior point method,(cid:96)1-norm regularized optimization,compressive sensing
更新于2025-09-23 15:22:29
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[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Joint Reconstruction of PET Attenuation and Activity from Scattered and Unscattered Data
摘要： In previous work, we have proposed scatter-to-attenuation reconstruction for positron emission tomography (PET). Scatter-to-attenuation reconstruction aims at recovering object attenuation information in the form of spatial electron-density distributions from pairs of coincident photons, one of which has been single-scattered. One idea is to interleave scatter-to-attenuation reconstruction, which inputs an activity distribution and outputs an attenuation map, with trues-to-activity reconstruction, which inputs said attenuation map and outputs an improved activity distribution. However, major uncertainties regarding the applicability of this approach revolve around a) the unknown impact of the initial activity estimate; b) evaluation of reconstructed activity distributions, and c) convergence to the correct solution. Methods: Using low-dimensional simulated PET data (mouse-sized, 18x18-voxels phantom), we start with mostly uniform initial activity and attenuation estimates and iteratively apply maximum-likelihood expectation-maximization (MLEM) and a maximum-likelihood gradient-ascent (MLGA) algorithm to update activity (from unscattered data) and attenuation (from scattered data), respectively. We evaluate results in terms of log-likelihoods of the expected scatter histograms, and normalized mean squared errors with respect to reference image-space distributions of activity and attenuation. Results: In our study, both attenuation and activity converged to the reference distributions, despite MLEM and MLGA starting with incorrect attenuation and activity estimates, respectively. Conclusion: The MLGA scatter-to-attenuation reconstruction algorithm, in combination with MLEM trues-to-activity reconstruction, jointly reconstructs attenuation maps and attenuation-corrected activity distributions from scattered and unscattered coincidences without reliance on a-priori information about the activity distribution.
关键词： image reconstruction,PET,attenuation,Compton scattering,algorithms
更新于2025-09-23 15:22:29
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XCT image reconstruction by a modified superiorized iteration and theoretical analysis
摘要： In this paper, we propose an improved iteration superiorization method for X-ray computed tomography image reconstruction. We simplify the classic superiorized iteration by removing two constraints imposed on the perturbation. A novel method is proposed to determine the perturbation amount and direction for the superiorized iteration simultaneously. Some theoretical properties (convergence for instance) of the superiorized iteration sequence with the proposed perturbation are analysed. We present a general proof for the convergence of ART-like iterations with summable perturbations. In addition, we prove the convergence of simultaneous iterations without the summable perturbation assumption. Experiments on simulated and real data not only verify the theoretical result but also show that the proposed algorithm is superior to the classic superiorized iteration and can reconstruct desirable images.
关键词： XCT image reconstruction,superiorization of iteration,proximity perturbation,algebraic method
更新于2025-09-23 15:22:29
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A linear state space model for photoacoustic imaging in an acoustic attenuating media
摘要： In photoacoustic imaging, ultrasound waves generated by a temperature rise after illumination of light absorbing structures are measured on the sample surface. These measurements are then used to reconstruct the optical absorption. We develop a method for reconstructing the absorption inside the sample based on a discrete linear state space reformulation of a partial differential equation that describes the propagation of the ultrasound waves. Fundamental properties of the corresponding state space model such as stability, observability and controllability are also analyzed. By using Stokes’ equation, the frequency dependent attenuation of the ultrasound waves is incorporated into our model, therefore the proposed method is of general nature. This approach allows for inhomogeneous probes with arbitrary absorption profiles and it accounts for the decrease in laser intensity due to absorption. Furthermore, it provides a method for optimizing the laser modulation signal such that the accuracy of the estimated absorption profile is maximized. Utilizing the optimized laser modulation signal yields an increase in reconstruction accuracy compared to short laser pulses as well as chirp modulation in many scenarios.
关键词： optimal temporal laser excitation,photoacoustic image reconstruction,acoustic attenuation,linear state space model
更新于2025-09-23 15:22:29
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Dual-modality optical projection tomography reconstruction method from fewer views
摘要： In optical projection tomography (OPT), for longitudinal living model studies, multiple measurements of the same sample are required at different time points. It is important to decrease both the total acquisition time and the light dose to the sample. We improved the ordered subsets expectation maximization reconstruction algorithm for OPT, which reduces the acquisition time and number of projections greatly compared with filtered back projection (FBP), and satisfactory reconstructed images are obtained. Using zebrafish, in transmission and fluorescence mode, we demonstrate the capability of the method to reconstruct image from downsampled projection subsets. The result shows that the reconstruction image quality of the proposed method using 30 projections is comparable to that of FBP using 720 projections. The total acquisition procedure can be finished in a few seconds. The method also provides OPT with the remarkable capability to resist noises and artifacts.
关键词： molecular imaging,image reconstruction,dual-modality OPT,preimaging calibration
更新于2025-09-23 15:22:29
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Robust 3D object reconstruction based on camera clustering with geodesic distance
摘要： This Letter presents a method that reconstructs 3D object using camera clustering and key camera selection to resolve scalability problem. To perform camera clustering, camera similarity is defined using geodesic distance and overlap constraint between cameras. Key cameras are then selected to reconstruct an object considering overlapping cameras and high curvature regions. As a result, it is achievable to relax increases in the execution time and the accumulated errors due to the scalability problems with a large number of cameras.
关键词： three-dimensional displays,image reconstruction,Clustering methods,Robot vision systems
更新于2025-09-23 15:22:29
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Maximum entropy based non-negative optoacoustic tomographic image reconstruction
摘要： Objective: Optoacoustic (photoacoustic) tomography is aimed at reconstructing maps of the initial pressure rise induced by the absorption of light pulses in tissue. In practice, due to inaccurate assumptions in the forward model, noise and other experimental factors, the images are often afflicted by artifacts, occasionally manifested as negative values. The aim of the work is to develop an inversion method which reduces the occurrence of negative values and improves the quantitative performance of optoacoustic imaging. Methods: We present a novel method for optoacoustic tomography based on an entropy maximization algorithm, which uses logarithmic regularization for attaining non-negative reconstructions. The reconstruction image quality is further improved using structural prior based fluence correction. Results: We report the performance achieved by the entropy maximization scheme on numerical simulation, experimental phantoms and in-vivo samples. Conclusion: The proposed algorithm demonstrates superior reconstruction performance by delivering non-negative pixel values with no visible distortion of anatomical structures. Significance: Our method can enable quantitative optoacoustic imaging, and has the potential to improve pre-clinical and translational imaging applications.
关键词： inverse problems,image reconstruction,Optical parameters,regularization theory,photoacoustic tomography
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Design Techniques for Incremental Non-Regular Image Sampling Patterns
摘要： Even though image signals are typically acquired on a regular two dimensional grid, there exist many scenarios where non-regular sampling is possible. Non-regular sampling can remove aliasing. In terms of the non-regular sampling patterns, there is a high degree of freedom in how to actually arrange the sampling positions. In literature, random patterns show higher reconstruction quality compared to regular patterns due to reduced aliasing effects. On the downside, random patterns feature large void areas which is also disadvantageous. In the scope of this work, we present two techniques to design optimized non-regular image sampling patterns for arbitrary sampling densities. Both techniques create incremental sampling patterns, i.e., one pixel position is added in each step until the desired sampling density is reached. Our proposed patterns increase the reconstruction quality by more than +0.5 dB in PSNR for a broad density range. Visual comparisons are provided.
关键词： Non-Regular Sampling,Image Reconstruction
更新于2025-09-23 15:22:29
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Improving the Signal-to-noise Ratio of Super Resolution Imaging Based on Single Pixel Camera
摘要： Based on the theories of single pixel camera and compressed sensing image reconstruction, the sparse basis, the projection method of measurement matrix and the signal reconstruction algorithm are optimized. Firstly, for the sparse representation of image, the restraint matrix is designed combining the characteristics of wavelet sparse coefficients to enhance the sparse representation ability of the discrete wavelet base, which improves the quality of image reconstruction and imaging by single pixel camera. Then in the single pixel camera system, the projection method is improved according to the characteristics of the DMD micro-mirror, and a new bilateral projection method based on the block diagonal measurement matrix is proposed to realize the super resolution imaging of the outdoor scene, reducing the number of measurement and improving the imaging quality. Finally, for the algorithm of image reconstruction, combining the characteristics of convex optimization and non-convex optimization algorithms, a new algorithm from convex optimization approximately to non convex optimization algorithm is proposed, and compared with traditional image reconstruction algorithm such as greedy pursuit algorithm, minimum norm algorithm and image interpolation, the peak signal to noise ratio (PSNR) and imaging quality of reconstructed images are effectively improved. The feasibility of the proposed methods is demonstrated by simulation experiments and imaging experiments of single pixel camera.
关键词： measurement matrix,Single pixel camera,sparse representation,super resolution,image reconstruction
更新于2025-09-23 15:22:29
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3D spectroscopic measurement of argon and metal vapour in MIG welding
摘要： Spectroscopic measurements for gas-metal arc (GMA) phenomena have been recently performed. The studies have reported that the metal vapour behaviour greatly affects the arc properties. However, they can be applied only to axially symmetric phenomena because of the assumption used for the measurement. GMA welding are normally performed with a travel speed, and most of the phenomena become axially asymmetric. This study constructed the simultaneous and multidirectional measurement system by 12 CCD cameras which can capture such axially asymmetric GMA phenomena. We measured the metal inert gas welding process with use of two types of narrowband interference filters for Ar I and Fe I during the one measurement, and observed axially asymmetrical intensity distributions in the globular and the spray transfer mode. We found that the globular transfer mode that is seemingly chaotic distribution can be regarded as the distribution where the deviation of Ar I is larger than Fe I from the axially symmetric double-ring distribution that consists of Ar I and Fe I.
关键词： image reconstruction,ML-EM method,CCD camera,globular transfer,interference filter,axially asymmetrical arc plasma,spray transfer,Optical emission spectroscopy
更新于2025-09-23 15:21:21