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Protocol optimization is critical in Computed Tomography (CT) to achieve high diagnostic image quality while minimizing radiation dose. However, due to the complex interdependencies among CT acquisition and reconstruction parameters,…

Purpose: Iterative projection reconstruction algorithms are currently the preferred reconstruction method in proton computed tomography (pCT). However, due to inconsistencies in the measured data arising from proton energy straggling and…

Medical Physics · Physics 2015-05-20 S. N. Penfold , R. W. Schulte , Y. Censor , A. B. Rosenfeld

Set projection algorithms are a class of algorithms used in ptychography to help improve the quality of the reconstructed images. The set projection step is important because it helps to ensure that the reconstructed image satisfies the…

Signal Processing · Electrical Eng. & Systems 2023-11-21 Wenjie Mei , Andrew M. Maiden

Single particle cryo-electron microscopy is a vital tool for 3D characterization of protein structures. A typical workflow involves acquiring projection images of a collection of randomly oriented particles, picking and classifying…

Image and Video Processing · Electrical Eng. & Systems 2021-03-22 S. V. Venkatakrishnan , Puneet Juneja , Hugh O'Neill

Image segmentation is an inherently ill-posed problem and thus requires regularization in order to limit the search space to reasonable solutions. A majority of segmentation methods integrates these regularization terms in one way or the…

Numerical Analysis · Mathematics 2018-10-31 Uri Nahum , Philippe C. Cattin

Finite mixture models are powerful tools for modelling and analyzing heterogeneous data. Parameter estimation is typically carried out using maximum likelihood estimation via the Expectation-Maximization (EM) algorithm. Recently, the…

Computation · Statistics 2020-05-15 Sharon X. Lee , Geoffrey J. McLachlan , Kaleb L. Leemaqz

This paper discusses the incorporation of local sparsity information, e.g. in each pixel of an image, via minimization of the $\ell^{1,\infty}$-norm. We discuss the basic properties of this norm when used as a regularization functional and…

Optimization and Control · Mathematics 2015-06-12 Pia Heins , Michael Moeller , Martin Burger

Deconvolving COMPTEL gamma-ray data into images presents a major methodological challenge. We developed a new algorithm called Multiresolution Regularized Expectation Maximization (MREM), which explicitly accounts for spatial correlations…

Existing vision tokenization isolates the optimization of vision tokenizers from downstream training, implicitly assuming the visual tokens can generalize well across various tasks, e.g., image generation and visual question answering. The…

Computer Vision and Pattern Recognition · Computer Science 2025-05-16 Wenxuan Wang , Fan Zhang , Yufeng Cui , Haiwen Diao , Zhuoyan Luo , Huchuan Lu , Jing Liu , Xinlong Wang

It's well-known that inverse problems are ill-posed and to solve them meaningfully one has to employ regularization methods. Traditionally, popular regularization methods have been the penalized Variational approaches. In recent years, the…

Machine Learning · Computer Science 2022-02-17 Abinash Nayak

Structural equation models (SEMs) are widely used in sciences, ranging from economics to psychology, to uncover causal relationships underlying a complex system under consideration and estimate structural parameters of interest. We study…

Machine Learning · Statistics 2020-10-21 Luofeng Liao , You-Lin Chen , Zhuoran Yang , Bo Dai , Zhaoran Wang , Mladen Kolar

We investigate projected scaled gradient (PSG) methods for convex minimization problems. These methods perform a descent step along a diagonally scaled gradient direction followed by a feasibility regaining step via orthogonal projection…

Optimization and Control · Mathematics 2015-07-28 W. Jin , Y. Censor , M. Jiang

The family of Expectation-Maximization (EM) algorithms provides a general approach to fitting flexible models for large and complex data. The expectation (E) step of EM-type algorithms is time-consuming in massive data applications because…

Computation · Statistics 2018-06-21 Sanvesh Srivastava , Glen DePalma , Chuanhai Liu

The Expectation Maximisation (EM) algorithm is widely used to optimise non-convex likelihood functions with latent variables. Many authors modified its simple design to fit more specific situations. For instance, the Expectation (E) step…

Statistics Theory · Mathematics 2022-05-03 Thomas Lartigue , Stanley Durrleman , Stéphanie Allassonnière

Entity Resolution (ER) is a critical data cleaning task for identifying records that refer to the same real-world entity. In the era of Big Data, traditional batch ER is often infeasible due to volume and velocity constraints, necessitating…

Databases · Computer Science 2026-01-05 Dimitrios Karapiperis , George Papadakis , Vassilios Verykios

Ill-posed linear inverse problems (ILIP), such as restoration and reconstruction, are a core topic of signal/image processing. A standard approach to deal with ILIP uses a constrained optimization problem, where a regularization function is…

Optimization and Control · Mathematics 2016-11-15 Manya V. Afonso , Jose M. Bioucas-Dias , Mario A. T. Figueiredo

The linear inverse problem emerges from various real-world applications such as Image deblurring, inpainting, etc., which are still thrust research areas for image quality improvement. In this paper, we have introduced a new algorithm…

Signal Processing · Electrical Eng. & Systems 2022-11-29 Avinash Kumar , Sujit Kumar Sahoo

The data consistency for the physical forward model is crucial in inverse problems, especially in MR imaging reconstruction. The standard way is to unroll an iterative algorithm into a neural network with a forward model embedded. The…

Image and Video Processing · Electrical Eng. & Systems 2023-06-28 Guanxiong Luo , Mengmeng Kuang , Peng Cao

Self-attention mechanism has been widely used for various tasks. It is designed to compute the representation of each position by a weighted sum of the features at all positions. Thus, it can capture long-range relations for computer vision…

Computer Vision and Pattern Recognition · Computer Science 2024-05-28 Xia Li , Zhisheng Zhong , Jianlong Wu , Yibo Yang , Zhouchen Lin , Hong Liu