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Westin, Carl-Fredrik
Alternative names
Publications (10 of 36) Show all publications
Lundberg, J., Westin, C.-F., Arvola, M., Holmlid, S. & Josefsson, B. (2018). Cognitive work analysis and conceptual designing for unmanned air traffic management in cities. In: : . Paper presented at Proceedings of the 36th European Conference on Cognitive Ergonomics (ECCE'19), Utrecht, Netherlands, September 5-7, 2018 (pp. 1-4). New York: ACM Press
Open this publication in new window or tab >>Cognitive work analysis and conceptual designing for unmanned air traffic management in cities
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2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Cognitive Work Analysis (CWA) is an appropriate approach in high-stakes domains, such as Air Traffic Management (ATM). It provides focus on human expert performance in regular as well as contingency situations. However, CWA is not suitable for the design of a first-of-a-kind system, since there is nothing to analyze before the start of the design process. In 2017, unmanned traffic management (UTM) for intense drone traffic in cities was such a system. Making things worse, the UTM system has to be in place before the traffic, since it provides basic safety. In this paper we present conceptual designing as a bootstrapping approach to CWA for UTM as a first-of-a-kind system.

Place, publisher, year, edition, pages
New York: ACM Press, 2018
Keywords
cognitive work analysis, conceptual designing, work domain analysis, unmanned aircraft traffic management
National Category
Human Computer Interaction
Identifiers
urn:nbn:se:liu:diva-157104 (URN)10.1145/3232078.3232082 (DOI)2-s2.0-85055319921 (Scopus ID)978-1-4503-6449-2 (ISBN)
Conference
Proceedings of the 36th European Conference on Cognitive Ergonomics (ECCE'19), Utrecht, Netherlands, September 5-7, 2018
Projects
UTM50
Available from: 2019-05-28 Created: 2019-05-28 Last updated: 2019-06-13Bibliographically approved
Nordin, T., Zsigmond, P., Pujol, S., Westin, C.-F. & Wårdell, K. (2018). Computer models in deep brain stimulation based on diffusion MRI. In: : . Paper presented at Medicinteknikdagarna, 9-10 oktober 2018, Umeå, Sverige.
Open this publication in new window or tab >>Computer models in deep brain stimulation based on diffusion MRI
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2018 (English)Conference paper, Oral presentation only (Refereed)
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-152025 (URN)
Conference
Medicinteknikdagarna, 9-10 oktober 2018, Umeå, Sverige
Available from: 2018-10-17 Created: 2018-10-17 Last updated: 2018-10-17
Nordin, T., Zsigmond, P., Pujol, S., Westin, C.-F. & Wårdell, K. (2018). Deep brain stimulation: Patient-specific electrical field simulation. In: : . Paper presented at XXIIIrd congress of the European Society for Stereotactic and Functional Neurosurgery, 26-29 september 2018, Edinburgh, Scotland (ESSFN).
Open this publication in new window or tab >>Deep brain stimulation: Patient-specific electrical field simulation
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2018 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-152027 (URN)
Conference
XXIIIrd congress of the European Society for Stereotactic and Functional Neurosurgery, 26-29 september 2018, Edinburgh, Scotland (ESSFN)
Available from: 2018-10-17 Created: 2018-10-17 Last updated: 2018-10-17
Özarslan, E., Yolcu, C., Herberthson, M., Knutsson, H. & Westin, C.-F. (2018). Influence of the Size and Curvedness of Neural Projections on the Orientationally Averaged Diffusion MR Signal. Frontiers in Physics, 6, 1-10, Article ID 17.
Open this publication in new window or tab >>Influence of the Size and Curvedness of Neural Projections on the Orientationally Averaged Diffusion MR Signal
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2018 (English)In: Frontiers in Physics, E-ISSN 2296-424X, Vol. 6, p. 1-10, article id 17Article in journal (Refereed) Published
Abstract [en]

Neuronal and glial projections can be envisioned to be tubes of infinitesimal diameter as far as diffusion magnetic resonance (MR) measurements via clinical scanners are concerned. Recent experimental studies indicate that the decay of the orientationally-averaged signal in white-matter may be characterized by the power-law, Ē(q) ∝ q−1, where q is the wavenumber determined by the parameters of the pulsed field gradient measurements. One particular study by McKinnon et al. [1] reports a distinctively faster decay in gray-matter. Here, we assess the role of the size and curvature of the neurites and glial arborizations in these experimental findings. To this end, we studied the signal decay for diffusion along general curves at all three temporal regimes of the traditional pulsed field gradient measurements. We show that for curvy projections, employment of longer pulse durations leads to a disappearance of the q−1 decay, while such decay is robust when narrow gradient pulses are used. Thus, in clinical acquisitions, the lack of such a decay for a fibrous specimen can be seen as indicative of fibers that are curved. We note that the above discussion is valid for an intermediate range of q-values as the true asymptotic behavior of the signal decay is Ē(q) ∝ q−4 for narrow pulses (through Debye-Porod law) or steeper for longer pulses. This study is expected to provide insights for interpreting the diffusion-weighted images of the central nervous system and aid in the design of acquisition strategies.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2018
National Category
Biomedical Laboratory Science/Technology Radiology, Nuclear Medicine and Medical Imaging Atom and Molecular Physics and Optics Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-145426 (URN)10.3389/fphy.2018.00017 (DOI)
Available from: 2018-03-02 Created: 2018-03-02 Last updated: 2018-03-27Bibliographically approved
Özarslan, E., Yolcu, C., Herberthson, M., Westin, C.-F. & Knutsson, H. (2017). Effective Potential for Magnetic Resonance Measurements of Restricted Diffusion. Frontiers in Physics, 5, Article ID 68.
Open this publication in new window or tab >>Effective Potential for Magnetic Resonance Measurements of Restricted Diffusion
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2017 (English)In: Frontiers in Physics, E-ISSN 2296-424X, Vol. 5, article id 68Article in journal (Refereed) Published
Abstract [en]

The signature of diffusive motion on the NMR signal has been exploited to characterize the mesoscopic structure of specimens in numerous applications. For compartmentalized specimens comprising isolated subdomains, a representation of individual pores is necessary for describing restricted diffusion within them. When gradient waveforms with long pulse durations are employed, a quadratic potential profile is identified as an effective energy landscape for restricted diffusion. The dependence of the stochastic effective force on the center-of-mass position is indeed found to be approximately linear (Hookean) for restricted diffusion even when the walls are sticky. We outline the theoretical basis and practical advantages of our picture involving effective potentials.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2017
National Category
Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-143866 (URN)10.3389/fphy.2017.00068 (DOI)
Available from: 2017-12-22 Created: 2017-12-22 Last updated: 2018-03-27Bibliographically approved
Westin, C.-F., Knutsson, H., Pasternak, O., Szczepankiewicz, F., Özarslan, E., van Westen, D., . . . Nilsson, M. (2016). Q-space trajectory imaging for multidimensional diffusion MRI of the human brain. NeuroImage, 135, 345-362
Open this publication in new window or tab >>Q-space trajectory imaging for multidimensional diffusion MRI of the human brain
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2016 (English)In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 135, p. 345-362Article in journal (Refereed) Published
Abstract [en]

This work describes a new diffusion MR framework for imaging and modeling of microstructure that we call q-space trajectory imaging (QTI). The QTI framework consists of two parts: encoding and modeling. First we propose q-space trajectory encoding, which uses time-varying gradients to probe a trajectory in q-space, in contrast to traditional pulsed field gradient sequences that attempt to probe a point in q-space. Then we propose a microstructure model, the diffusion tensor distribution (DTD) model, which takes advantage of additional information provided by QTI to estimate a distributional model over diffusion tensors. We show that the QTI framework enables microstructure modeling that is not possible with the traditional pulsed gradient encoding as introduced by Stejskal and Tanner. In our analysis of QTI, we find that the well-known scalar b-value naturally extends to a tensor-valued entity, i.e., a diffusion measurement tensor, which we call the b-tensor. We show that b-tensors of rank 2 or 3 enable estimation of the mean and covariance of the DTD model in terms of a second order tensor (the diffusion tensor) and a fourth order tensor. The QTI framework has been designed to improve discrimination of the sizes, shapes, and orientations of diffusion microenvironments within tissue. We derive rotationally invariant scalar quantities describing intuitive microstructural features including size, shape, and orientation coherence measures. To demonstrate the feasibility of QTI on a clinical scanner, we performed a small pilot study comparing a group of five healthy controls with five patients with schizophrenia. The parameter maps derived from QTI were compared between the groups, and 9 out of the 14 parameters investigated showed differences between groups. The ability to measure and model the distribution of diffusion tensors, rather than a quantity that has already been averaged within a voxel, has the potential to provide a powerful paradigm for the study of complex tissue architecture.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
DDE, DTI, Diffusion MRI, Diffusion tensor distribution, Microscopic anisotropy, Microscopic fractional anisotropy μFA, QTI, SDE, TDE, q-space, q-space trajectory
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-129986 (URN)10.1016/j.neuroimage.2016.02.039 (DOI)000378047600031 ()26923372 (PubMedID)
Note

Funding agencies:The authors acknowledge the NIH grants R01MH074794, R01MH092862, R01MH102377, R01AG042512, P41EB015902, P41EB015898, U01CA199459, and the Swedish Research Council (VR) grants 2012-3682, 2011-5176, 2014-3910, TUBITAK-EU COFUND project no. 114C015, ITEA/Vinnova/13031 BENEFIT, and Swedish Foundation for Strategic Research (SSF) grant AM13-0090.

Available from: 2016-07-04 Created: 2016-07-04 Last updated: 2017-11-28Bibliographically approved
Knutsson, H., Herberthson, M. & Westin, C.-F. (2015). An Iterated Complex Matrix Approach for Simulation and Analysis of Diffusion MRI Processes. In: MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2015, PT I: . Paper presented at 18th International Conference on Medical Image Computing and Computer-Assisted Intervention (MICCAI) (pp. 61-68). SPRINGER INT PUBLISHING AG, 9349
Open this publication in new window or tab >>An Iterated Complex Matrix Approach for Simulation and Analysis of Diffusion MRI Processes
2015 (English)In: MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2015, PT I, SPRINGER INT PUBLISHING AG , 2015, Vol. 9349, p. 61-68Conference paper, Published paper (Refereed)
Abstract [en]

We present a novel approach to investigate the properties of diffusion weighted magnetic resonance imaging (dMRI). The process of restricted diffusion of spin particles in the presence of a magnetic field is simulated by an iterated complex matrix multiplication approach. The approach is based on first principles and provides a flexible, transparent and fast simulation tool. The experiments carried out reveals fundamental features of the dMRI process. A particularly interesting observation is that the induced speed of the local spatial spin angle rate of change is highly shift variant. Hence, the encoding basis functions are not the complex exponentials associated with the Fourier transform as commonly assumed. Thus, reconstructing the signal using the inverse Fourier transform leads to large compartment estimation errors, which is demonstrated in a number of 1D and 2D examples. In accordance with previous investigations the compartment size is under-estimated. More interestingly, however, we show that the estimated shape is likely to be far from the true shape using state of the art clinical MRI scanners.

Place, publisher, year, edition, pages
SPRINGER INT PUBLISHING AG, 2015
Series
Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 9349
National Category
Medical Biotechnology Mathematics
Identifiers
urn:nbn:se:liu:diva-124149 (URN)10.1007/978-3-319-24553-9_8 (DOI)000366205700008 ()978-3-319-24553-9 (ISBN)978-3-319-24552-2 (ISBN)
Conference
18th International Conference on Medical Image Computing and Computer-Assisted Intervention (MICCAI)
Available from: 2016-01-22 Created: 2016-01-19 Last updated: 2018-01-25
Sjölund, J., Nilsson, M., Topgaard, D., Westin, C.-F. & Knutsson, H. (2015). Constrained optimization of gradient waveforms for generalized diffusion encoding. Journal of magnetic resonance, 261, 157-168
Open this publication in new window or tab >>Constrained optimization of gradient waveforms for generalized diffusion encoding
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2015 (English)In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 261, p. 157-168Article in journal (Refereed) Published
Abstract [en]

Diffusion MRI is a useful probe of tissue structure. The prototypical diffusion encoding sequence, the single pulsed field gradient, has recently been challenged with the introduction of more general gradient waveforms. Out of these, we focus on q-space trajecory imaging, which generalizes the scalar b-value to a tensor valued property. To take full advantage of its capabilities, it is imperative to respect the constraints imposed by the hardware, while at the same time maximizing the diffusion encoding strength. We formulate this as a constrained optimization problem that accomodates constraints on maximum gradient amplitude, slew rate, coil heating and positioning of radiofrequency pulses. The power of this approach is demonstrated by a comparison with previous work on optimization of isotropic diffusion sequences, showing possible gains in diffusion weighting or in heat dissipation, which in turn means increased signal or reduced scan-times.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Diffusion MR; Generalized gradient waveforms; Q-space trajectory imaging; Optimization; Hardware constraints
National Category
Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-115795 (URN)10.1016/j.jmr.2015.10.012 (DOI)000367212100021 ()
Note

On the day of the defence date the status of this article was Manuscript.

Available from: 2015-03-20 Created: 2015-03-20 Last updated: 2018-01-16Bibliographically approved
Eriksson, S., Lasic, S., Nilsson, M., Westin, C.-F. & Topgaard, D. (2015). NMR diffusion-encoding with axial symmetry and variable anisotropy: Distinguishing between prolate and oblate microscopic diffusion tensors with unknown orientation distribution. Journal of Chemical Physics, 142(10), 104201
Open this publication in new window or tab >>NMR diffusion-encoding with axial symmetry and variable anisotropy: Distinguishing between prolate and oblate microscopic diffusion tensors with unknown orientation distribution
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2015 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 142, no 10, p. 104201-Article in journal (Refereed) Published
Abstract [en]

We introduce a nuclear magnetic resonance method for quantifying the shape of axially symmetric microscopic diffusion tensors in terms of a new diffusion anisotropy metric, D-Delta, which has unique values for oblate, spherical, and prolate tensor shapes. The pulse sequence includes a series of equal-amplitude magnetic field gradient pulse pairs, the directions of which are tailored to give an axially symmetric diffusion-encoding tensor b with variable anisotropy b(Delta). Averaging of data acquired for a range of orientations of the symmetry axis of the tensor b renders the method insensitive to the orientation distribution function of the microscopic diffusion tensors. Proof-of-principle experiments are performed on water in polydomain lyotropic liquid crystals with geometries that give rise to microscopic diffusion tensors with oblate, spherical, and prolate shapes. The method could be useful for characterizing the geometry of fluid-filled compartments in porous solids, soft matter, and biological tissues. (C) 2015 Author(s).

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2015
National Category
Medical Biotechnology
Identifiers
urn:nbn:se:liu:diva-117230 (URN)10.1063/1.4913502 (DOI)000350978000046 ()25770532 (PubMedID)
Note

Funding Agencies|Swedish Foundation for Strategic Research [AM13-0090]; Swedish Research Council [2009-6794, 2014-3910, K2011-52x-21737-01-3]; Swedish Cancer Society [04 0421]; National Institute of Health (NIH) [R01MH074794, P41EB015902]

Available from: 2015-04-22 Created: 2015-04-21 Last updated: 2017-12-04
Knutsson, H. & Westin, C.-F. (2014). An Information Theoretic Approach to Optimal Q-space Sampling. In: ISMRM-ESMRMB 2014: . Paper presented at Joint Annual Meeting ISMRM-ESMRMB 2014, 10-17 May 2014, Milan, Italy.
Open this publication in new window or tab >>An Information Theoretic Approach to Optimal Q-space Sampling
2014 (English)In: ISMRM-ESMRMB 2014, 2014Conference paper, Poster (with or without abstract) (Other academic)
National Category
Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-110418 (URN)
Conference
Joint Annual Meeting ISMRM-ESMRMB 2014, 10-17 May 2014, Milan, Italy
Projects
CMIVCADICS
Funder
Swedish Research CouncilNIH (National Institute of Health)
Available from: 2014-09-11 Created: 2014-09-11 Last updated: 2014-10-08
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