Relevant publications

Dr. Michael Zibulevsky

T. Weiss, O. Senouf, S. Vedula, O. Michailovich, M. Zibulevsky, A. M. Bronstein, PILOT: Physics-Informed Learned Optimal Trajectories for Accelerated MRI, arXiv:1909.05773, 2019 details

PILOT: Physics-Informed Learned Optimal Trajectories for Accelerated MRI

T. Weiss, O. Senouf, S. Vedula, O. Michailovich, M. Zibulevsky, A. M. Bronstein
arXiv:1909.05773, 2019
Picture for PILOT: Physics-Informed Learned Optimal Trajectories for Accelerated MRI

Magnetic Resonance Imaging (MRI) has long been considered to be among “the gold standards” of diagnostic medical imaging. The long acquisition times, however, render MRI prone to motion artifacts, let alone their adverse contribution to the relatively high costs of MRI examination. Over the last few decades, multiple studies have focused on the development of both physical and post-processing methods for accelerated acquisition of MRI scans. These two approaches, however, have so far been addressed separately. On the other hand, recent works in optical computational imaging have demonstrated growing success of the concurrent learning-based design of data acquisition and image reconstruction schemes. Such schemes have already demonstrated substantial effectiveness, leading to considerably shorter acquisition times and improved quality of image reconstruction. Inspired by this initial success, in this work, we propose a novel approach to the learning of optimal schemes for conjoint acquisition and reconstruction of MRI scans, with the optimization, carried out simultaneously with respect to the time-efficiency of data acquisition and the quality of resulting reconstructions. To be of practical value, the schemes are encoded in the form of general k-space trajectories, whose associated magnetic gradients are constrained to obey a set of predefined hardware requirements (as defined in terms of, e.g., peak currents and maximum slew rates of magnetic gradients). With this proviso in mind, we propose a novel algorithm for the end-to-end training of a combined acquisition-reconstruction pipeline using a deep neural network with differentiable forward- and backpropagation operators. We also demonstrate the effectiveness of the proposed solution in application to both image reconstruction and image segmentation, reporting substantial improvements in terms of acceleration factors as well as the quality of these end tasks.

S. Vedula, O. Senouf, G. Zurakov, A. M. Bronstein, O. Michailovich, M. Zibulevsky, Learning beamforming in ultrasound imaging, Proc. Medical Imaging with Deep Learning (MIDL), 2019 details

Learning beamforming in ultrasound imaging

S. Vedula, O. Senouf, G. Zurakov, A. M. Bronstein, O. Michailovich, M. Zibulevsky
Proc. Medical Imaging with Deep Learning (MIDL), 2019
Picture for Learning beamforming in ultrasound imaging
Medical ultrasound (US) is a widespread imaging modality owing its popularity to cost-efficiency, portability, speed, and lack of harmful ionizing radiation. In this paper, we demonstrate that replacing the traditional ultrasound processing pipeline with a data-driven, learnable counterpart leads to signi cant improvement in image quality. Moreover, we demonstrate that greater improvement can be achieved through a learning-based design of the transmitted beam patterns simultaneously with learning an image reconstruction pipeline. We evaluate our method on an in-vivo fi rst-harmonic cardiac ultrasound dataset acquired from volunteers and demonstrate the signi cance of the learned pipeline and transmit beam patterns on the image quality when compared to standard transmit and receive beamformers used in high frame-rate US imaging. We believe that the presented methodology provides a fundamentally di erent perspective on the classical problem of ultrasound beam pattern design.
T. Weiss, S. Vedula, O. Senouf, A. M. Bronstein, O. Michailovich, M. Zibulevsky, Learning fast magnetic resonance imaging, arXiv: 1905.09324, 2019 details

Learning fast magnetic resonance imaging

T. Weiss, S. Vedula, O. Senouf, A. M. Bronstein, O. Michailovich, M. Zibulevsky
arXiv: 1905.09324, 2019
Picture for Learning fast magnetic resonance imaging

Magnetic Resonance Imaging (MRI) is considered today the golden-standard modality for soft tissues. The long acquisition times, however, make it more prone to motion artifacts as well as contribute to the relatively high costs of this examination. Over the years, multiple studies concentrated on designing reduced measurement schemes and image reconstruction schemes for MRI, however, these problems have been so far addressed separately. On the other hand, recent works in optical computational imaging have demonstrated growing success of the simultaneous learning-based design of the acquisition and reconstruction schemes manifesting significant improvement in the reconstruction quality with a constrained time budget. Inspired by these successes, in this work, we propose to learn accelerated MR acquisition schemes (in the form of Cartesian trajectories) jointly with the image reconstruction operator. To this end, we propose an algorithm for training the combined acquisition-reconstruction pipeline end-to-end in a differentiable way. We demonstrate the significance of using the learned Cartesian trajectories at different speed up rates.

O. Senouf, S. Vedula, T. Weiss, A. M. Bronstein, O. Michailovich, M. Zibulevsky, Self-supervised learning of inverse problem solvers in medical imaging, arXiv: 1905.09325, 2019 details

Self-supervised learning of inverse problem solvers in medical imaging

O. Senouf, S. Vedula, T. Weiss, A. M. Bronstein, O. Michailovich, M. Zibulevsky
arXiv: 1905.09325, 2019
Picture for Self-supervised learning of inverse problem solvers in medical imaging

In the past few years, deep learning-based methods have demonstrated enormous success for solving inverse problems in medical imaging. In this work, we address the following question: Given a set of measurements obtained from real imaging experiments, what is the best way to use a learnable model and the physics of the modality to solve the inverse problem and reconstruct the latent image? Standard supervised learning based methods approach this problem by collecting data sets of known latent images and their corresponding measurements. However, these methods are often impractical due to the lack of availability of appropriately sized training sets, and, more generally, due to the inherent difficulty in measuring the “groundtruth” latent image. In light of this, we propose a self-supervised approach to training inverse models in medical imaging in the absence of aligned data. Our method only requiring access to the measurements and the forward model at training. We showcase its effectiveness on inverse problems arising in accelerated magnetic resonance imaging (MRI).

O. Senouf, S. Vedula, G. Zurakhov, A. M. Bronstein, M. Zibulevsky, O. Michailovich, D. Adam, D. Blondheim, High frame-rate cardiac ultrasound imaging with deep learning, Proc. Int'l Conf. Medical Image Computing & Computer Assisted Intervention (MICCAI), 2018 details

High frame-rate cardiac ultrasound imaging with deep learning

O. Senouf, S. Vedula, G. Zurakhov, A. M. Bronstein, M. Zibulevsky, O. Michailovich, D. Adam, D. Blondheim
Proc. Int'l Conf. Medical Image Computing & Computer Assisted Intervention (MICCAI), 2018
Picture for High frame-rate cardiac ultrasound imaging with deep learning

Cardiac ultrasound imaging requires a high frame rate in order to capture rapid motion. This can be achieved by multi-line acquisition (MLA), where several narrow-focused received lines are obtained from each wide-focused transmitted line. This shortens the acquisition time at the expense of introducing block artifacts. In this paper, we propose a data-driven learning-based approach to improve the MLA image quality. We train an end-to-end convolutional neural network on pairs of real ultrasound cardiac data, acquired through MLA and the corresponding single-line acquisition (SLA). The network achieves a significant improvement in image quality for both 5- and 7-line MLA resulting in a decorrelation measure similar to that of SLA while having the frame rate of MLA.

S. Vedula, O. Senouf, G. Zurakhov, A. M. Bronstein, M. Zibulevsky, O. Michailovich, D. Adam, D. Gaitini, High quality ultrasonic multi-line transmission through deep learning, Proc. Machine Learning for Medical Image Reconstruction (MLMIR), 2018 details

High quality ultrasonic multi-line transmission through deep learning

S. Vedula, O. Senouf, G. Zurakhov, A. M. Bronstein, M. Zibulevsky, O. Michailovich, D. Adam, D. Gaitini
Proc. Machine Learning for Medical Image Reconstruction (MLMIR), 2018

Frame rate is a crucial consideration in cardiac ultrasound imaging and 3D sonography. Several methods have been proposed in the medical ultrasound literature aiming at accelerating the image acquisition. In this paper, we consider one such method called multi-line transmission (MLT), in which several evenly separated focused beams are transmitted simultaneously. While MLT reduces the acquisition time, it comes at the expense of a heavy loss of contrast due to the interactions between the beams (cross-talk artifact). In this paper, we introduce a data-driven method to reduce the artifacts arising in MLT. To this end, we propose to train an end-to-end convolutional neural network consisting of correction layers followed by a constant apodization layer. The network is trained on pairs of raw data obtained through MLT and the corresponding single-line transmission (SLT) data. Experimental evaluation demonstrates signi cant improvement both in the visual image quality and in objective measures such as contrast ratio and contrast-to-noise ratio, while preserving resolution unlike traditional apodization-based methods. We show that the proposed method is able to generalize
well across di erent patients and anatomies on real and phantom data.

S. Vedula, O. Senouf, A. M. Bronstein, O. V. Michailovich, M. Zibulevsky, Towards CT-quality ultrasound imaging using deep learning, arXiv:1710.06304, 2017 details

Towards CT-quality ultrasound imaging using deep learning

S. Vedula, O. Senouf, A. M. Bronstein, O. V. Michailovich, M. Zibulevsky
arXiv:1710.06304, 2017
Picture for Towards CT-quality ultrasound imaging using deep learning

The cost-effectiveness and practical harmlessness of ultra- sound imaging have made it one of the most widespread tools for medical diagnosis. Unfortunately, the beam-forming based image formation produces granular speckle noise, blur- ring, shading and other artifacts. To overcome these effects, the ultimate goal would be to reconstruct the tissue acoustic properties by solving a full wave propagation inverse prob- lem. In this work, we make a step towards this goal, using Multi-Resolution Convolutional Neural Networks (CNN). As a result, we are able to reconstruct CT-quality images from the reflected ultrasound radio-frequency(RF) data obtained by simulation from real CT scans of a human body. We also show that CNN is able to imitate existing computationally heavy despeckling methods, thereby saving orders of magni- tude in computations and making them amenable to real-time applications.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, On separation of semitransparent dynamic images from static background, Proc. Int'l Conf. on Independent Component Analysis and Blind Signal Separation, 2006 details

On separation of semitransparent dynamic images from static background

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky
Proc. Int'l Conf. on Independent Component Analysis and Blind Signal Separation, 2006
Picture for On separation of semitransparent dynamic images from static background

Presented here is the problem of recovering a dynamic image superimposed on a static background. Such a problem is ill-posed and may arise e.g. in imaging through semireflective media, in separation of an illumination image from a reflectance image, in imaging with diffraction phenomena, etc. In this work we study regularization of this problem in spirit of Total Variation and general sparsifying transformations.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Quasi maximum likelihood blind deconvolution: super- an sub-Gaussianity versus consistency, IEEE Trans. Signal Processing, Vol. 53(7), 2005 details

Quasi maximum likelihood blind deconvolution: super- an sub-Gaussianity versus consistency

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky
IEEE Trans. Signal Processing, Vol. 53(7), 2005
Picture for Quasi maximum likelihood blind deconvolution: super- an sub-Gaussianity versus consistency

In this note we consider the problem of MIMO quasi maximum likelihood (QML) blind deconvolution. We examine two classes of estimators, which are commonly believed to be suitable for super- and sub-Gaussian sources. We state the consistency conditions and demonstrate a distribution, for which the studied estimators are unsuitable, in the sense that they are asymptotically unstable

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Relative optimization for blind deconvolution, IEEE Trans. on Signal Processing, Vol. 53(6), 2005 details

Relative optimization for blind deconvolution

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky
IEEE Trans. on Signal Processing, Vol. 53(6), 2005
Picture for Relative optimization for blind deconvolution

We propose a relative optimization framework for quasi-maximum likelihood (QML) blind deconvolution and the relative Newton method as its particular instance. The special Hessian structure allows fast Newton system construction and solution, resulting in a fast-convergent algorithm with iteration complexity comparable to that of gradient methods. We also propose the use of rational IIR restoration kernels, which constitute a richer family of filters than the traditionally used FIR kernels. We discuss different choices of non-linear functions suitable for deconvolution of super- and sub-Gaussian sources and formulate the conditions, under which the QML estimation is stable. Simulation results demonstrate the efficiency of the proposed methods.

M. M. Bronstein, A. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, Blind deconvolution of images using optimal sparse representations, IEEE Trans. on Image Processing, Vol. 14(6), 2005 details

Blind deconvolution of images using optimal sparse representations

M. M. Bronstein, A. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
IEEE Trans. on Image Processing, Vol. 14(6), 2005
Picture for Blind deconvolution of images using optimal sparse representations

The relative Newton algorithm, previously proposed for quasi-maximum likelihood blind source separation and blind deconvolution of one-dimensional signals is generalized for blind deconvolution of images. Smooth approximation of the absolute value is used in modeling the log probability density function, which is suitable for sparse sources. In addition, we propose a method of sparsification, which allows blind deconvolution of sources with arbitrary distribution, and show how to find optimal sparsifying transformations by training.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, Unmixing tissues: sparse component analysis in multi-contrast MRI, Proc. Int'l Conf. on Image Processing (ICIP), 2005 details

Unmixing tissues: sparse component analysis in multi-contrast MRI

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
Proc. Int'l Conf. on Image Processing (ICIP), 2005
Picture for Unmixing tissues: sparse component analysis in multi-contrast MRI

We pose the problem of tissue classification in MRI as a blind source separation (BSS) problem and solve it by means of sparse component analysis (SCA). Assuming that most MR images can be sparsely represented, we consider their optimal sparse representation. Sparse components define a physically-meaningful feature space for classification. We demonstrate our approach on simulated and real multi-contrast MRI data. The proposed framework is general in that it is applicable to other modalities of medical imaging as well, whenever the linear mixing model is applicable.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, Sparse ICA for blind separation of transmitted and reflected images, Int'l Journal of Imaging Science and Technology (IJIST), Vol. 15(1), 2005 details

Sparse ICA for blind separation of transmitted and reflected images

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
Int'l Journal of Imaging Science and Technology (IJIST), Vol. 15(1), 2005
Picture for Sparse ICA for blind separation of transmitted and reflected images

We address the problem of recovering a scene recorded through a semi-reflecting medium (i.e. planar lens), with a virtual reflected image being superimposed on the image of the scene transmitted through the semi-reflective lens. Recent studies propose imaging through a linear polarizer at several orientations to estimate the reflected and the transmitted components in the scene. In this stud,y we extend the sparse ICA (SPICA) technique and apply it to the problem of separating the image of the scene without having any a priori knowledge about its structure or statistics. Recent novel advances in the SPICA approach are discussed. Simulation and experimental results demonstrate the efficacy of the proposed methods.

M. M. Bronstein, A. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi,, Optimal sparse representations for blind source separation and blind deconvolution: a learning approach, Proc. Int'l Conf. on Image Processing (ICIP), 2004 details

Optimal sparse representations for blind source separation and blind deconvolution: a learning approach

M. M. Bronstein, A. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi,
Proc. Int'l Conf. on Image Processing (ICIP), 2004
Picture for Optimal sparse representations for blind source separation and blind deconvolution: a learning approach

We present a generic approach, which allows to adapt sparse blind deconvolution and blind source separation algorithms to arbitrary sources. The key idea is to bring the problem to the case in which the underlying sources are sparse by applying a sparsifying transformation on the mixtures. We present simulation results and show that such transformation can be found by training. Properties of the optimal sparsifying transformation are highlighted by an example with aerial images.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, Fast relative Newton algorithm for blind deconvolution of images, Proc. Int'l Conf. on Image Processing (ICIP), 2004 details

Fast relative Newton algorithm for blind deconvolution of images

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
Proc. Int'l Conf. on Image Processing (ICIP), 2004
Picture for Fast relative Newton algorithm for blind deconvolution of images

We present an efficient Newton-like algorithm for quasi-maximum likelihood (QML) blind deconvolution of images. This algorithm exploits the sparse structure of the Hessian. An optimal distribution-shaping approach by means of sparsification allows one to use simple and convenient sparsity prior for processing of a wide range of natural images. Simulation results demonstrate the efficiency of the proposed method.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Blind source separation using block-coordinate relative Newton method, Signal Processing, Vol. 84(8), 2004 details

Blind source separation using block-coordinate relative Newton method

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky
Signal Processing, Vol. 84(8), 2004
Picture for Blind source separation using block-coordinate relative Newton method

Presented here is a generalization of the relative Newton method, recently proposed for quasi maximum likelihood blind source separation. Special structure of the Hessian matrix allows performing block-coordinate Newton descent, which significantly reduces the algorithm computational complexity and boosts its performance. Simulations based on artificial and real data showed that the separation quality using the proposed algorithm is superior compared to other accepted blind source separation methods.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Blind source separation using the block-coordinate relative Newton method, Proc. Int'l Conf. on Independent Component Analysis and Blind Signal Separation, Lecture Notes in Comp. Science No. 3195, Springer, 2004 details

Blind source separation using the block-coordinate relative Newton method

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky
Proc. Int'l Conf. on Independent Component Analysis and Blind Signal Separation, Lecture Notes in Comp. Science No. 3195, Springer, 2004
Picture for Blind source separation using the block-coordinate relative Newton method

Presented here is a generalization of the modified relative Newton method, recently proposed by Zibulevsky for quasi-maximum likelihood blind source separation. The special structure of the Hessian matrix allows to perform block-coordinate Newton descent, which significantly reduces the algorithm computational complexity and boosts its performance. Simulations based on artificial and real data show that the separation quality using the proposed algorithm outperforms other accepted blind source separation methods.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, QML blind deconvolution: asymptotic analysis, Proc. Int'l Conf. on Independent Component Analysis and Blind Signal Separation, 2004 details

QML blind deconvolution: asymptotic analysis

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
Proc. Int'l Conf. on Independent Component Analysis and Blind Signal Separation, 2004
Picture for QML blind deconvolution: asymptotic analysis

Blind deconvolution is considered as a problem of quasi-maximum likelihood (QML) estimation of the restoration kernel. Simple closed-form expressions for the asymptotic estimation error are derived. The asymptotic performance bounds coincide with the Cramér-Rao bounds, when the true ML estimator is used. Conditions for asymptotic stability of the QML estimator are derived. Special cases when the estimator is super-efficient are discussed.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, Optimal sparse representations for blind deconvolution of images, Proc. Int'l Conf. on Independent Component Analysis and Blind Signal Separation, 2004 details

Optimal sparse representations for blind deconvolution of images

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
Proc. Int'l Conf. on Independent Component Analysis and Blind Signal Separation, 2004
Picture for Optimal sparse representations for blind deconvolution of images

The relative Newton algorithm, previously proposed for quasi-maximum likelihood blind source separation and blind deconvolution of one-dimensional signals is generalized for blind deconvolution of images. Smooth approximation of the absolute value is used in modeling the log probability density function, which is suitable for sparse sources. We propose a method of sparsification, which allows blind deconvolution of sources with arbitrary distribution, and show how to find optimal sparsifying transformations by training.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, Quasi maximum likelihood blind deconvolution of images acquired through scattering media, Proc. Int'l Symposium on Biomedical Imaging (ISBI), 2004 details

Quasi maximum likelihood blind deconvolution of images acquired through scattering media

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
Proc. Int'l Symposium on Biomedical Imaging (ISBI), 2004
Picture for Quasi maximum likelihood blind deconvolution of images acquired through scattering media

We address the problem of restoration of images obtained through a scattering medium. We present an efficient quasi-maximum likelihood blind deconvolution approach based on the fast relative Newton algorithm and optimal distribution shaping approach (sparsification), which allows to use simple and convenient sparsity prior for a wide class of images. Simulation results prove the efficiency of the proposed method.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, Optimal nonlinear line-of-flight estimation in positron emission tomography, IEEE Trans. on Nuclear Science, Vol. 50(3), 2003 details

Optimal nonlinear line-of-flight estimation in positron emission tomography

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
IEEE Trans. on Nuclear Science, Vol. 50(3), 2003
Picture for Optimal nonlinear line-of-flight estimation in positron emission tomography

We consider detection of high-energy photons in PET using thick scintillation crystals. Parallax effect and multiple Compton interactions such crystals significantly reduce the accuracy of conventional detection methods. In order to estimate the photon line of flight based on photomultiplier responses, we use asymptotically optimal nonlinear techniques, implemented by feedforward and radial basis function (RBF) neural networks. Incorporation of information about angles of incidence of photons significantly improves the accuracy of estimation. The proposed estimators are fast enough to perform detection, using conventional computers. Monte-Carlo simulation results show that our approach significantly outperforms the conventional Anger algorithm.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, Separation of semireflective layers using Sparse ICA, Proc. Int'l Conf. on Acoustics Speech and Signal Processing (ICASSP), 2003 details

Separation of semireflective layers using Sparse ICA

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
Proc. Int'l Conf. on Acoustics Speech and Signal Processing (ICASSP), 2003
Picture for Separation of semireflective layers using Sparse ICA

We address the problem of Blind Source Separation (BSS) of superimposed images and, in particular, consider the recovery of a scene recorded through a semi-refective medium (e.g. glass windshield) from its mixture with a virtual reflected image. We extend the Sparse ICA (SPICA) approach to BSS and apply it to the separation of the desired image from the superimposed images, without having any a priori knowledge about its structure and/or statistics. Advances in the SPICA approach are discussed. Simulations and experimental results illustrate the efficiency of the proposed approach, and of its specific implementation in a simple algorithm of a low computational cost. The approach and the algorithm are generic in that they can be adapted and applied to a wide range of BSS problems involving one-dimensional signals or images.

M. M. Bronstein, A. M. Bronstein, M. Zibulevsky, H. Azhari, Reconstruction in ultrasound diffraction tomography using non-uniform FFT, IEEE Trans. on Medical Imaging, Vol. 21(11), 2002 details

Reconstruction in ultrasound diffraction tomography using non-uniform FFT

M. M. Bronstein, A. M. Bronstein, M. Zibulevsky, H. Azhari
IEEE Trans. on Medical Imaging, Vol. 21(11), 2002
Picture for Reconstruction in ultrasound diffraction tomography using non-uniform FFT

We show an iterative reconstruction framework for diffraction ultrasound tomography. The use of broadband illumination allows a significant reduction of the number of projections compared to straight ray tomography. The proposed algorithm makes use of the forward nonuniform fast Fourier transform (NUFFT) for iterative Fourier inversion. Incorporation of total variation regularization allows the reduction of noise and Gibbs phenomena while preserving the edges. The complexity of the NUFFT-based reconstruction is comparable to the frequency domain interpolation (gridding) algorithm, whereas the reconstruction accuracy (in sense of the L2 and the L norm) is better.

M. M. Bronstein, A. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, Iterative reconstruction in diffraction tomography using non-uniform fast Fourier transform, Proc. Int'l Symposium on Biomedical Imaging (ISBI), 2002 details

Iterative reconstruction in diffraction tomography using non-uniform fast Fourier transform

M. M. Bronstein, A. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
Proc. Int'l Symposium on Biomedical Imaging (ISBI), 2002
Picture for Iterative reconstruction in diffraction tomography using non-uniform fast Fourier transform

We show an iterative reconstruction framework for diffraction ultrasound tomography. The use of broadband illumination allows the number of projections to be reduced significantly compared to straight ray tomography. The proposed algorithm makes use of fast forward non-uniform Fourier transform (NUFFT) for iterative Fourier inversion. Incorporation of total variation regularization allows noise and Gibbs phenomena to be reduced whilst preserving the edges.

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi, Optimal nonlinear estimation of photon coordinates in PET, Proc. Int'l Symposium on Biomedical Imaging (ISBI), 2002 details

Optimal nonlinear estimation of photon coordinates in PET

A. M. Bronstein, M. M. Bronstein, M. Zibulevsky, Y. Y. Zeevi
Proc. Int'l Symposium on Biomedical Imaging (ISBI), 2002
Picture for Optimal nonlinear estimation of photon coordinates in PET

We consider detection of high-energy photons in PET using thick scintillation crystals. Parallax effect and multiple Compton interactions in this type of crystals significantly reduce the accuracy of conventional detection methods. In order to estimate the scintillation point coordinates based on photomultiplier responses, we use asymptotically optimal nonlinear techniques, implemented by feed-forward neural networks, radial basis functions (RBF) networks, and neuro-fuzzy systems. Incorporation of information about angles of incidence of photons significantly improves the accuracy of estimation. The proposed estimators are fast enough to perform detection using conventional computers.