Searched for: author%3A%22Remis%2C+R.F.%22
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Zimmerling, J.T. (author), Druskin, Vladimir (author), Guddati, Murthy (author), Cherkaev, Elena (author), Remis, R.F. (author)
We present a reduced-order model (ROM) methodology for inverse scattering problems in which the ROMs are data-driven, i.e. they are constructed directly from data gathered by sensors. Moreover, the entries of the ROM contain localised information about the coefficients of the wave equation. We solve the inverse problem by embedding the ROM in...
journal article 2024
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de Vos, B. (author), Remis, R.F. (author), Webb, A. (author)
MRI systems have a thin conducting layer placed between the gradient and RF coils, this acts as a shield at the RF-frequency, minimizing noise coupled into the experiment, and decreasing the coupling between the RF and gradient coils. Ideally, this layer should be transparent to the gradient fields to reduce eddy currents. In this work the...
journal article 2024
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de Vos, B. (author), Remis, R.F. (author), Webb, A. (author)
Objective: Low-cost low-field point-of-care MRI systems are used in many different applications. System design has correspondingly different requirements in terms of imaging field-of-view, spatial resolution and magnetic field strength. In this work an iterative framework has been created to design a cylindrical Halbach-based magnet along...
journal article 2023
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Brink, Wyger M. (author), Remis, R.F. (author), Webb, A. (author)
Purpose: High permittivity dielectric pads are known to be effective for tailoring the RF field and improving image quality in high field MRI. Despite a number of studies reporting benign specific absorption rate (SAR) effects, their “universal” safety remains an open concern. In this work, we evaluate the impact of the insulation material in...
journal article 2023
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de Vos, B. (author), Remis, R.F. (author), Webb, A. (author)
Purpose: Concomitant gradient fields have been extensively studied at clinical field strengths. However, their effects have not yet been modeled for low-field point-of-care (POC) systems. The purpose of this work is to characterize the effects associated with concomitant fields for POC Halbach-array-based systems. Methods: The concomitant...
journal article 2023
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de Leeuw den Bouter, M.L. (author), Ippolito, G. (author), O’Reilly, T. P.A. (author), Remis, R.F. (author), van Gijzen, M.B. (author), Webb, A. (author)
Low-field MRI scanners are significantly less expensive than their high-field counterparts, which gives them the potential to make MRI technology more accessible all around the world. In general, images acquired using low-field MRI scanners tend to be of a relatively low resolution, as signal-to-noise ratios are lower. The aim of this work is...
journal article 2022
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Goedmakers, C.M.W. (author), Pereboom, L. M. (author), Schoones, J. W. (author), de Leeuw den Bouter, M.L. (author), Remis, R.F. (author), Staring, M. (author), Vleggeert-Lankamp, C. L.A. (author)
review 2022
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Fuchs, P.S. (author), Remis, R.F. (author)
In this article, we present full-wave signal models for magnetic and electric field measurements in magnetic resonance imaging (MRI). Our analysis is based on a scattering formalism in which the presence of an object or body is taken into account via an electric scattering source. We show that these signal models can be evaluated, provided...
journal article 2022
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Brink, Wyger M. (author), Yousefi, Sahar (author), Bhatnagar, Prernna (author), Remis, R.F. (author), Staring, M. (author), Webb, A. (author)
Purpose: Parallel RF transmission (PTx) is one of the key technologies enabling high quality imaging at ultra-high fields (≥7T). Compliance with regulatory limits on the local specific absorption rate (SAR) typically involves over-conservative safety margins to account for intersubject variability, which negatively affect the utilization of...
journal article 2022
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de Leeuw den Bouter, M.L. (author), van Gijzen, M.B. (author), Remis, R.F. (author)
In this paper we present a magnetic resonance imaging (MRI) technique that is based on multiplicative regularization. Instead of adding a regularizing objective function to a data fidelity term, we multiply by such a regularizing function. By following this approach, no regularization parameter needs to be determined for each new data set...
journal article 2021
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Leijsen, R.L. (author), Brink, W. (author), An, X. (author), Webb, A. (author), Remis, R.F. (author)
A new local method for magnetic resonance electrical properties tomography (EPT), dubbed transverse-EPT (T-EPT), is introduced. This approach iteratively optimizes the dielectric properties (conductivity and permittivity) and the z-component of the electric field strength, exploiting the locally E-polarized field structure typically present...
journal article 2021
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Koolstra, Kirsten (author), Remis, R.F. (author)
Purpose: To learn a preconditioner that accelerates parallel imaging (PI) and compressed sensing (CS) reconstructions. Methods: A convolutional neural network (CNN) with residual connections was used to train a preconditioning operator. Training and validation data were simulated using 50% brain images and 50% white Gaussian noise images....
journal article 2021
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de Vos, B. (author), Parsa, Javad (author), Abdulrazaq, Zaynab (author), Teeuwisse, Wouter M. (author), Van Speybroeck, Camille D.E. (author), de Gans, D.H. (author), Remis, R.F. (author), O’Reilly, Tom (author), Webb, A. (author)
Low-field permanent magnet-based MRI systems are finding increasing use in portable, sustainable and point-of-care applications. In order to maximize performance while minimizing cost many components of such a system should ideally be designed specifically for low frequency operation. In this paper we describe recent developments in...
journal article 2021
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de Leeuw den Bouter, M.L. (author), van den Berg, P.M. (author), Remis, R.F. (author)
In this paper we discuss an imaging method when the object has known support and its spatial Fourier transform is only known on a certain k-space undersampled pattern. The simple conjugate gradient least squares algorithm applied to the corresponding truncated Fourier transform equation produces reconstructions that are basically of a similar...
journal article 2021
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Leijsen, R.L. (author), Brink-van Caspel, W.M. (author), At Van Den Berg, Cornelis (author), Webb, A. (author), Remis, R.F. (author)
Electrical properties tomography (EPT) is an imaging method that uses a magnetic resonance (MR) system to non-invasively determine the spatial distribution of the conductivity and permittivity of the imaged object. This manuscript starts by providing clear definitions about the data required for, and acquired in, EPT, followed by comprehensively...
journal article 2021
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Stijnman, Peter R.S. (author), Mandija, Stefano (author), Fuchs, P.S. (author), van den Berg, Cornelis A.T. (author), Remis, R.F. (author)
Purpose: To remove the necessity of the tranceive phase assumption for CSI-EPT and show electrical properties maps reconstructed from measured data obtained using a standard 3T birdcage body coil setup. Methods: The existing CSI-EPT algorithm is reformulated to use the transceive phase rather than relying on the transceive phase assumption....
journal article 2021
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Leijsen, Reijer L. (author), Brink, Wyger M. (author), Webb, A. (author), Remis, R.F. (author)
Three-dimensional contrast source inversion-electrical properties tomography (3-D CSI-EPT) is an iterative reconstruction method that estimates the electrical properties of tissue from transmit field magnetic resonance data. However, in order to bring 3-D CSI-EPT into practice for complex tissue structures and to understand the origin and...
journal article 2021
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de Leeuw den Bouter, M.L. (author), van Gijzen, M.B. (author), Remis, R.F. (author)
In an earlier paper, we generalized the CGME (Conjugate Gradient Minimal Error) algorithm to the ℓ<sub>2</sub>-regularized weighted least-squares problem. Here, we use this Generalized CGME method to reconstruct images from actual signals measured using a low-field MRI scanner. We analyze the convergence of both GCGME and the classical...
conference paper 2021
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De Vos, Bart (author), Fuchs, P.S. (author), O'Reilly, Thomas (author), Webb, A. (author), Remis, R.F. (author)
In this article, we design and construct gradient coils for a Halbach permanent-magnet array magnetic resonance (MR) scanner. The target field method, which is widely applied for the case of axial static magnetic fields, has been developed for a transverse static magnetic field as produced by a Halbach permanent-magnet array. Using this...
journal article 2020
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Zimmerling, J.T. (author), Remis, R.F. (author)
Determining the electromagnetic field response of photonic and plasmonic resonators is a formidable task in general. Field expansions in terms of quasi-normal modes (QNMs) are often used, since only a few of these modes are typically required for an accurate field description. We show that by exploiting the structure of Maxwell’s equations,...
journal article 2020
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