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Hoogerbrugge, L.A. (author), van Dongen, K.W.A. (author), Verschuur, D.J. (author)The phenomenon of wave conversions, where acoustic, pressure (P) waves are converted to elastic, shear (S) waves is commonly disregarded in seismic imaging, which can lead to lower-quality images in regions with strong reflectors. While a number of methods exist which do take wave conversions into account, most deal with P- and S-waves...conference paper 2024
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Saputera, D.H. (author), Jakobsen, M. (author), Jahani, N. (author), van Dongen, K.W.A. (author), Alyaev, S. (author), Eikrem, K.S. (author)Inversion of electromagnetic induction log while drilling provides structural information around borehole for geosteering decision process. Imaging a complex three-dimensional (3D) anisotropic formation is very challenging due to the significant cost of the forward solver. To overcome this challenge, we have developed an inversion algorithm...conference paper 2024
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Saputera, D. H. (author), Jakobsen, M. (author), van Dongen, K.W.A. (author), Jahani, N. (author), Eikrem, K. S. (author), Alyaev, S. (author)The deployment of electromagnetic (EM) induction tools while drilling is one of the standard routines for assisting the geosteering decision-making process. The conductivity distribution obtained through the inversion of the EM induction log can provide important information about the geological structure around the borehole. To image the 3-D...journal article 2024
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Saputera, D.H. (author), Jakobsen, M. (author), Jahani, N. (author), Alyaev, S. (author), Eikrem, K.S. (author), van Dongen, K.W.A. (author)Real-time 3D imaging of the induction log is essential for improving the decision-making process in geosteering. To fulfill this need, we investigated various strategies for reducing the computational cost for 3D modelling of induction logs using the integral equation (IE) method, including the use of iterative Krylov solver, convolution with...conference paper 2023
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van der Neut, J.R. (author), Hoogerbrugge, L.A. (author), van Dongen, K.W.A. (author), Verschuur, D.J. (author)Full Wavefield Migration (FWMig) is an inversion-based seismic imaging modality that incorporates multiple reflections via one-way wave propagation. The flexible Full Wavefield Modelling (FWMod) engine that undergirds FWMig can be extended to address both compressional and converted waves. To take care of the angle-dependent nature of reflection...conference paper 2023
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Jakobsen, Morten (author), Xiang, Kui (author), van Dongen, K.W.A. (author)We present an iterative nonlinear inverse scattering algorithm for high-resolution acoustic imaging of density and velocity variations. To solve the multi-parameter nonlinear direct scattering problem, the acoustic wave equation for inhomogeneous media in the frequency domain is transformed into a vectorial integral equation of the Lippmann...journal article 2023
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Zhao, Wenzhao (author), Fan, Yuling (author), Wang, Hongjian (author), Gemmeke, Hartmut (author), van Dongen, K.W.A. (author), Hopp, Torsten (author), Hesser, Jürgen (author)Objective. The image reconstruction of ultrasound computed tomography is computationally expensive with conventional iterative methods. The fully learned direct deep learning reconstruction is promising to speed up image reconstruction significantly. However, for direct reconstruction from measurement data, due to the lack of real labeled...journal article 2023
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Scherders, Eva M.L. (author), Verschuur, D.J. (author), van Dongen, K.W.A. (author)Imaging by inversion of acoustic or electromagnetic wave fields have applications in a wide variety of areas, such as non-destructive testing, biomedical applications, and geophysical exploration. Unfortunately, each modality suffers from its own application-specific limitations, typically being difficulties in distinguishing different...conference paper 2022
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Ramirez, Ana B. (author), Abreo, Sergio A. (author), van Dongen, K.W.A. (author)With full waveform inversion (FWI) all available information enclosed in the recorded wavefield - including multiple scattering, dispersion, and diffraction - is used to obtain accurate images showing quantitative information of the tissue parameters. These non-linear inversion methods are implemented either in the time or in the frequency...conference paper 2022
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Hoogerbrugge, L.A. (author), van Dongen, K.W.A. (author), Verschuur, D.J. (author)Conventional Full Wavefield Migration (FWM) is a full-wavefield inversion method based on recursively applying one-way convolutional propagation and reflection operators in the space-frequency domain at every depth level. Therefore, it struggles to model diving waves and image steep reflectors accurately. In this paper, the Interface Contrast...conference paper 2022
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Taskin, U. (author), Suzuki, Atsuro (author), Terada, Takahide (author), Tsubota, Yushi (author), van Dongen, K.W.A. (author)Quantitative images showing the speed of sound proffle of the breast may be obtained by employing full-waveform inversion (FWI) methods on the measured data. These reconstruction methods work well for both dense and normal breasts. Contrast source inversion (CSI) is a frequency domain FWI method. In literature, many examples of successful...conference paper 2022
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Taskin, U. (author), van der Neut, J.R. (author), Gemmeke, Hartmut (author), van Dongen, K.W.A. (author)Whole breast ultrasound scanning systems are used to screen a women’s breast for suspicious lesions. Typically, the transducers are located at fixed positions at relatively large distances from the breast to avoid any contact with the breast. Unfortunately, these large distances give rise to large spatial domains to be imaged. These large...journal article 2020
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Ouyang, B. (author), Li, Yanlu (author), Kruidhof, Marten (author), Horsten, R.C. (author), Baets, Roel (author), van Dongen, K.W.A. (author), Caro-Schuurman, J. (author)We report a highly sensitive ultrasound sensor based on an integrated photonics silicon Mach-Zehnder interferometer (MZI). One arm of the MZI is located on a thin membrane, acting as the sensing part of the device. Ultrasound waves excite the membrane's vibrational mode, thus inducing modulation of the MZI transmission. The measured sensor...conference paper 2020
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Taskin, U. (author), van Dongen, K.W.A. (author)Multi-parameter inversion for medical ultrasound leads to an improved tissue classification. In general, simultaneous reconstruction of volume density of mass and compressibility would require knowledge of the particle velocity field along with the pressure field. However, in practice the particle velocity field is not measured. Here, the...journal article 2020
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Zhao, Wenzhao (author), Wang, Hongjian (author), Gemmeke, Hartmut (author), van Dongen, K.W.A. (author), Hopp, Torsten (author), Hesser, Jürgen (author)Image reconstruction of ultrasound computed tomography based on the wave equation is able to show much more structural details than simpler ray-based image reconstruction methods. However, to invert the wave-based forward model is computationally demanding. To address this problem, we develop an efficient fully learned image reconstruction...journal article 2020
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Taskin, U. (author), Solberg Eikrem, Kjersti (author), Naevdal, Geir (author), Jakobsen, Morten (author), Verschuur, D.J. (author), van Dongen, K.W.A. (author)Transcranial ultrasound has been used to image the brain since 1942. Currently, it is regaining interest and full-waveform inversion (FWI) methods are now employed to reconstruct speed-of-sound profiles of the brain. Many of these methods require a good starting model. Here, we test the applicability of contrast source inversion (CSI) as a...conference paper 2020
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Meles, G.A. (author), van der Neut, J.R. (author), van Dongen, K.W.A. (author), Wapenaar, C.P.A. (author)Wavefield focusing can be achieved by Time-Reversal Mirrors, which involve in- and output signals that are infinite in time and waves propagating through the entire medium. Here, an alternative solution for wavefield focusing is presented. This solution is based on a new integral representation where in- and output signals are finite in time,...conference paper 2019
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van der Neut, J.R. (author), Fokkema, J.T. (author), van den Berg, P.M. (author), Zapf, Michael (author), Ruiter, Nicole V. (author), Taskin, U. (author), van Dongen, K.W.A. (author)Synthetic-aperture (SA) imaging is a popular method to visualize the reflectivity of an object from ultrasonic reflections. The method yields an image of the (volume) contrast in acoustic impedance with respect to the embedding. Typically, constant mass density is assumed in the underlying derivation. Due to the band-limited nature of the...journal article 2019
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Meles, G.A. (author), van der Neut, J.R. (author), van Dongen, K.W.A. (author), Wapenaar, C.P.A. (author)Wavefield focusing is often achieved by time-reversal mirrors, where wavefields emitted by a source located at the focal point are evaluated at a closed boundary and sent back, after time-reversal, into the medium from that boundary. Mathematically, time-reversal mirrors are derived from closed-boundary integral representations of reciprocity...journal article 2019
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van Dongen, K.W.A. (author), de Blécourt, A.J. (author), Lens, E. (author), Schaart, D.R. (author), Vos, F.M. (author)In proton therapy high energy protons are used to irradiate a tumor. Ideally, the delivered proton dose distribution is measured during treatment to ensure patient safety and treatment effectiveness. Here we investigate if we can use the ionoacoustic wave field to monitor the actual proton dose distribution for the two most commonly used proton...journal article 2019
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