Searched for: author:"Remis, R.F."
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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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de Leeuw den Bouter, M.L. (author), Gecmen, Dilan (author), Meijer, Angeline (author), de Gans, D.H. (author), Middelplaats, L.N.M. (author), Remis, R.F. (author), van Gijzen, M.B. (author)
More than 6,000 infants develop hydrocephalus in East Africa every year. Magnetic Resonance Imaging is the preferred technique to diagnose hydrocephalus. In countries such as Uganda, MRI is unaffordable at even major referral hospitals. In order to provide a sustainable diagnostic tool we are developing an inexpensive and easy-to-use MRI...
conference paper 2020
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van Gemert, J.H.F. (author), Brink, Wyger M. (author), Remis, R.F. (author), Webb, A. (author)
PURPOSE: One of the main concerns in fetal MRI is the radiofrequency power that is absorbed both by the mother and the fetus. Passive shimming using high permittivity materials in the form of "dielectric pads" has previously been shown to increase the formula presented efficiency and homogeneity in different applications, while reducing the...
journal article 2019
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Leijsen, R.L. (author), Brink, Wyger M. (author), Remis, R.F. (author), Webb, A. (author)
Model-based electrical properties tomography (EPT; [1,2]) reconstruction with 3-D Contrast Source Inversion-EPT (CSI-EPT; [3,4]) has high potential, but is inherently sensitive to small errors in the model used. Here we assess its sensitivity to errors in the incident electromagnetic (EM) fields due to coupling of the coil to the sample (loading...
conference paper 2019
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Stijnman, P.R.S. (author), Tokaya, Janot P. (author), van Gemert, J.H.F. (author), Luijten, Peter R. (author), Pluim, Josien P.W. (author), Brink, Wyger M. (author), Remis, R.F. (author), van den Berg, Cornelis A.T. (author), Raaijmakers, Alexander J. E. (author)
Purpose: Patients who have medical metallic implants, e.g. orthopaedic implants and pacemakers, often cannot undergo an MRI exam. One of the largest risks is tissue heating due to the radio frequency (RF) fields. The RF safety assessment of implants is computationally demanding. This is due to the large dimensions of the transmit coil...
journal article 2019
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Leijsen, R.L. (author), Fuchs, P.S. (author), Brink, Wyger (author), Webb, A. (author), Remis, R.F. (author)
The main objective of electrical-property tomography (EPT) is to retrieve dielectric tissue parameters from B <sub>1</sub> <sup>+</sup> data as measured by a magnetic-resonance (MR) scanner. This is a so-called hybrid inverse problem in which data are defined inside the reconstruction domain of interest. In this paper, we discuss recent and...
journal article 2019
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Leijsen, R.L. (author), van den Berg, Cornelis (author), Webb, A. (author), Remis, R.F. (author), Mandija, Stefano (author)
Magnetic resonance electrical properties tomography (MR-EPT) is a technique used to estimate the conductivity and permittivity of tissues from MR measurements of the transmit magnetic field. Different reconstruction methods are available; however, all these methods present several limitations, which hamper the clinical applicability. Standard...
journal article 2019
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Koolstra, K. (author), van Gemert, J.H.F. (author), Börnert, Peter (author), Webb, A. (author), Remis, R.F. (author)
Purpose: Design of a preconditioner for fast and efficient parallel imaging (PI) and compressed sensing (CS) reconstructions for Cartesian trajectories. Theory: PI and CS reconstructions become time consuming when the problem size or the number of coils is large, due to the large linear system of equations that has to be solved in l<sub>1<...
journal article 2019
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de Leeuw den Bouter, M.L. (author), van Gijzen, M.B. (author), Remis, R.F. (author)
We consider the MRI physics in a low-field MRI scanner, in which permanent magnets are used to generate a magnetic field in the millitesla range. A model describing the relationship between measured signal and image is derived, resulting in an ill-posed inverse problem. In order to solve it, a regularization penalty is added to the least-squares...
journal article 2019
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Fuchs, P.S. (author), Leijsen, R.L. (author), Remis, R.F. (author)
CSI-EPT is an Electrical Properties Tomography (EPT) reconstruction method that uses a Contrast Source Inversion (CSI) optimization approach to retrieve the conductivity and permittivity profiles of tissue based on -data. The method can handle variations in tissue profiles and was originally implemented for profile reconstructions in the...
conference paper 2019
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van Gemert, Jeroen (author), Brink, Wyger (author), Webb, A. (author), Remis, R.F. (author)
Purpose: High-permittivity materials in the form of flexible “dielectric pads” have proved very useful for addressing RF inhomogeneities in high field MRI systems. Finding the optimal design of such pads is, however, a tedious task, reducing the impact of this technique. We present an easy-to-use software tool which allows researchers and...
journal article 2019
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van Gemert, J.H.F. (author), Brink, W.M. (author), Webb, A. (author), Remis, R.F. (author)
Inhomogeneities in the transmit radio frequency magnetic field ( {\text{B}}-{1}^{+} ) reduce the quality of magnetic resonance (MR) images. This quality can be improved by using high-permittivity pads that tailor the {\text{B}}-{1}^{+} fields. The design of an optimal pad is application-specific and not straightforward and would therefore...
journal article 2018
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Fuchs, P.S. (author), Mandija, Stefano (author), Stijnman, Peter R.S. (author), Brink, Wyger M. (author), van den Berg, Cornelis A.T. (author), Remis, R.F. (author)
In this paper, we present an efficient dedicated electrical properties tomography (EPT) algorithm (called first-order current density EPT ) that exploits the particular radio frequency field structure, which is present in the midplane of a birdcage coil, to reconstruct conductivity and permittivity maps in this plane from B ^ + 1 data. The...
journal article 2018
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Zimmerling, J.T. (author), Druskin, Vladimir (author), Zaslavsky, Mikhail (author), Remis, R.F. (author)
We have developed several Krylov projection-based model-order reduction techniques to simulate electromagnetic wave propagation and diffusion in unbounded domains. Such techniques can be used to efficiently approximate transfer function field responses between a given set of sources and receivers and allow for fast and memory-efficient...
journal article 2018
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Leijsen, R.L. (author), Brink, Wyger M. (author), van den Berg, Cornelis A.T. (author), Webb, A. (author), Remis, R.F. (author)
Contrast source inversion &amp;#x2013; electrical properties tomography (CSI-EPT) is an iterative reconstruction method to retrieve the electrical properties (EPs) of tissues from MR data. The method is based on integral representations of the electromagnetic (EM) field and has been shown to allow EP reconstructions of small structures as...
journal article 2018
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Balidemaj, E. (author), van den Berg, Cornelis A.T. (author), van Lier, Astrid L.H.M.W. (author), Nederveen, Aart J. (author), Stalpers, Lukas J.A. (author), Crezee, Hans (author), Remis, R.F. (author)
Specific absorption rate (SAR) assessment is essential for safety purposes during MR acquisition. Online SAR assessment is not trivial and requires, in addition, knowledge of the electric tissue properties and the electric fields in the human anatomy. In this study, the potential of the recently developed CSI-EPT method to reconstruct SAR...
journal article 2016
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Zimmerling, J.T. (author), Wei, L. (author), Urbach, H.P. (author), Remis, R.F. (author)
We present a Krylov model-order reduction approach to efficiently compute the spontaneous decay (SD) rate of arbitrarily shaped 3D nanosized resonators. We exploit the symmetry of Maxwell’s equations to efficiently construct so-called reduced-order models that approximate the SD rate of a quantum emitter embedded in a resonating nanostructure....
journal article 2016
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Druskin, V. (author), Remis, R.F. (author)
The Krylov subspace projection approach is a well-established tool for the reducedorder modeling of dynamical systems in the time domain. In this paper, we address the main issues obstructing the application of this powerful approach to the time-domain solution of exterior wave problems. We use frequency-independent perfectly matched layers to...
journal article 2013
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Remis, R.F. (author)
journal article 2004
Searched for: author:"Remis, R.F."
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