| 1. |
- Reymbaut, A., et al.
(författare)
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Clinical Research with Advanced Diffusion Encoding Methods in MRI
- 2020
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Ingår i: Advanced Diffusion Encoding Methods in MRI. - Cambridge : Royal Society of Chemistry. - 2044-2548 .- 2044-253X. ; 2020-January:24, s. 406-429
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Bokkapitel (refereegranskat)abstract
- This chapter offers a comprehensive summary of applications of advanced diffusion encoding methods in MRI within a narrowly defined area of in vivo human measurements with imaging read-out and voxel-by-voxel data analysis. The list of methods comprises tensor-valued encoding to investigate cell densities, shapes, and orientations in heterogeneous tissues, time/frequency-dependent encoding for estimating structural length scales, adjustable velocity-encoding to monitor flow in the microcapillary network, double encoding with varying mixing times to assess diffusional exchange between distinct tissue microenvironments and across cell membranes, and relaxation-diffusion correlation to resolve and separately characterize tissue microenvironments in terms of their local chemical composition and microstructure. The shown examples include proof-of-concept measurements on healthy volunteers, pilot investigations of pathologies, and clinical research involving 10-100 subjects. Studied organs include brain, breast, prostate, liver, kidney, placenta, muscle, and peripheral nerve, with examples of pathologies from tumors, schizophrenia, multiple sclerosis, stroke, neurocysticercosis, pre-eclampsia, and chronic exertional compartment syndrome.
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| 2. |
- Topgaard, D., et al.
(författare)
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Translational Motion of Water in Biological Tissues-A Brief Primer
- 2020
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Ingår i: Advanced Diffusion Encoding Methods in MRI. - Cambridge : Royal Society of Chemistry. - 2044-2548 .- 2044-253X. - 9781788017268 - 9781788019910 ; 2020-January:24, s. 1-11
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Bokkapitel (refereegranskat)abstract
- As an introduction to the rigorous treatment of diffusion encoding in the rest of the book, this chapter gives simple non-mathematical explanations of the relations between the properties of biological tissues and the translational motion of the tissue water with the aim of conveying an intuitive feel of the relevant time and length scales and the level of detail of the information that can be obtained. The influence of biomembranes and macromolecules on water dynamics is reviewed from both molecular and cellular scale perspectives. The potentially complex motion patterns are decomposed into short-time diffusivity, restriction, anisotropy, flow, and exchange, which can be independently assessed and correlated with advanced diffusion encoding methods in MRI.
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| 3. |
- Ferreira, T. M., et al.
(författare)
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NMR Studies of Nonionic Surfactants
- 2013
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Ingår i: Annual Reports on NMR Spectroscopy. - : Elsevier. - 0066-4103. ; 79, s. 73-127
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Tidskriftsartikel (refereegranskat)abstract
- NMR has contributed greatly to our current understanding of self-association, phase behaviour, and molecular dynamics in aqueous systems of oligo(ethylene oxide) mono-alkyl ether (CmEn) nonionic surfactants, which are extensively used in both basic scientific studies and technical applications as emulsifying agents and detergents. This review provides a comprehensive but concise overview of the various NMR techniques that have been applied to nonionic surfactants. We describe conventional experimental procedures, such as the measurement of quadrupole splittings, nuclear relaxation times, and self-diffusion coefficients to characterize liquid crystalline phases, micelles, and microemulsions, as well as more advanced imaging and diffusion-diffusion 2D correlation approaches to investigate the structure of phase-separated systems and the spatial organization of anisotropic liquid crystalline domains on the micro- to millimetre length scales.
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| 4. |
- Francisco, J D, et al.
(författare)
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Liquid crystalline properties and extractability of monoolein-water systems by supercritical carbon dioxide
- 2003
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - 0927-7757. ; 213:1, s. 69-78
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Tidskriftsartikel (refereegranskat)abstract
- The influence of phase structure on the extraction recovery of monoolein from monoolein-water systems by supercritical carbon dioxide was investigated. Two monoolein-water mi tures at concentrations of 9 wt% water and 18 wt% water, respectively, were studied. H-2-NMR was used to monitor changes of the phase structures in supercritical conditions. The results showed that the phase structure and the water-monoolein interactions play a role on the extraction yield. The monoolein recovery was higher in the 9 wt% water sample in which L-alpha phase was present compared to the 18 wt% water sample in which the L-alpha melted to yield a L-2 phase. When the phase structures were the same in both samples, the extraction recovery was determined by the solubility properties of the components of the system. The changes due to the presence of supercritical carbon dioxide were shown also to depend on the water concentration of the monoolein-water mixture besides the temperature. The 18 wt% mixture showed a L-2 phase structure in all the range of the temperature investigated while the 9 wt% water mixture showed phase changes from L-alpha phase to L-2 phase in the same temperature range. (C) 200 Elsevier Science B.V. All rights reserved.
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| 5. |
- König, Nico, et al.
(författare)
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Spherical Micelles with Nonspherical Cores : Effect of Chain Packing on the Micellar Shape
- 2020
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; , s. 10686-10698
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembly of amphiphilic polymers into micelles is an archetypical example of a "self-confined"system due to the formation of micellar cores with dimensions of a few nanometers. In this work, we investigate the chain packing and resulting shape of Cn-PEOx micelles with semicrystalline cores using small/wide-angle X-ray scattering (SAXS/WAXS), contrast-variation small-angle neutron scattering (SANS), and nuclear magnetic resonance spectroscopy (NMR). Interestingly, the n-alkyl chains adopt a rotator-like conformation and pack into prolate ellipses (axial ratio ϵ ≈ 0.5) in the "crystalline"region and abruptly arrange into a more spheroidal shape (ϵ ≈ 0.7) above the melting point. We attribute the distorted spherical shape above the melting point to thermal fluctuations and intrinsic rigidity of the n-alkyl blocks. We also find evidence for a thin dehydrated PEO layer (≤1 nm) close to the micellar core. The results provide substantial insight into the interplay between crystallinity and molecular packing in confinement and the resulting overall micellar shape.
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| 6. |
- Lundell, H., et al.
(författare)
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Multidimensional diffusion MRI with spectrally modulated gradients reveals unprecedented microstructural detail
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Characterization of porous media is essential in a wide range of biomedical and industrial applications. Microstructural features can be probed non-invasively by diffusion magnetic resonance imaging (dMRI). However, diffusion encoding in conventional dMRI may yield similar signatures for very different microstructures, which represents a significant limitation for disentangling individual microstructural features in heterogeneous materials. To solve this problem, we propose an augmented multidimensional diffusion encoding (MDE) framework, which unlocks a novel encoding dimension to assess time-dependent diffusion specific to structures with different microscopic anisotropies. Our approach relies on spectral analysis of complex but experimentally efficient MDE waveforms. Two independent contrasts to differentiate features such as cell shape and size can be generated directly by signal subtraction from only three types of measurements. Analytical calculations and simulations support our experimental observations. Proof-of-concept experiments were applied on samples with known and distinctly different microstructures. We further demonstrate substantially different contrasts in different tissue types of a post mortem brain. Our simultaneous assessment of restriction size and shape may be instrumental in studies of a wide range of porous materials, enable new insights into the microstructure of biological tissues or be of great value in diagnostics.
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| 7. |
- Naranjo, Isaac Daimiel, et al.
(författare)
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Multidimensional diffusion magnetic resonance imaging for characterization of tissue microstructure in breast cancer patients : A prospective pilot study
- 2021
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Ingår i: Cancers. - : MDPI AG. - 2072-6694. ; 13:7
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Tidskriftsartikel (refereegranskat)abstract
- Diffusion-weighted imaging is a non-invasive functional imaging modality for breast tumor characterization through apparent diffusion coefficients. Yet, it has so far been unable to intuitively inform on tissue microstructure. In this IRB-approved prospective study, we applied novel multidimensional diffusion (MDD) encoding across 16 patients with suspected breast cancer to evaluate its potential for tissue characterization in the clinical setting. Data acquired via custom MDD sequences was processed using an algorithm estimating non-parametric diffusion tensor distributions. The statistical descriptors of these distributions allow us to quantify tissue composition in terms of metrics informing on cell densities, shapes, and orientations. Additionally, signal fractions from specific cell types, such as elongated cells (bin1), isotropic cells (bin2), and free water (bin3), were teased apart. Histogram analysis in cancers and healthy breast tissue showed that cancers exhibited lower mean values of “size” (1.43 ± 0.54 × 10−3 mm2/s) and higher mean values of “shape” (0.47 ± 0.15) corresponding to bin1, while FGT (fibroglandular breast tissue) presented higher mean values of “size” (2.33 ± 0.22 × 10−3 mm2/s) and lower mean values of “shape” (0.27 ± 0.11) corresponding to bin3 (p < 0.001). Invasive carcinomas showed significant differences in mean signal fractions from bin1 (0.64 ± 0.13 vs. 0.4 ± 0.25) and bin3 (0.18 ± 0.08 vs. 0.42 ± 0.21) compared to ductal carcinomas in situ (DCIS) and invasive carcinomas with associated DCIS (p = 0.03). MDD enabled qualitative and quantitative evaluation of the composition of breast cancers and healthy glands.
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| 8. |
- Sparr, Emma, et al.
(författare)
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The stratum corneum barrier - From molecular scale to macroscopic properties
- 2023
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Ingår i: Current Opinion in Colloid & Interface Science. - : Elsevier. - 1359-0294 .- 1879-0399. ; 67
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Forskningsöversikt (refereegranskat)abstract
- The upper layer of our skin, the stratum corneum (SC), is a versatile material that combines mechanical strength with efficient barrier function. In this paper, we discuss these macroscopic properties of SC in relation to recent findings on molecular responses and structural diversity in SC protein and lipids. We put particular focus on the intermediate (colloidal) length scale and how the different SC substructures are organized with respect to each other, including effects of nonequilibrium conditions in the skin with respect to the gradients in water and other components.
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| 9. |
- Topgaard, Daniel, et al.
(författare)
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NMR spectroscopy in inhomogeneous B-0 and B-1 fields with non-linear correlation
- 2005
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Ingår i: Journal of Magnetic Resonance. - : Elsevier BV. - 1096-0856 .- 1090-7807. ; 175:1, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Resolved NMR spectra from samples in inhomogeneous B-0 and B-1 fields can be obtained with the so-called "ex situ" methodology, employing a train of composite or adiabatic z-rotation RF pulses to periodically refocus the inhomogeneous broadening during the detection of the time-domain signal. Earlier schemes relied on a linear correlation between the inhomogeneous B0 and B, fields. Here the pulse length, bandwidth, and amplitude of the adiabatic pulses of the hyperbolic secant type are adjusted to improve the refocusing for a setup with non-linear correlation. The field correlation is measured using a two-dimensional nutation experiment augmented with a third dimension with varying RF carrier frequency accounting for off-resonance effects. The pulse optimization is performed with a computer algorithm using the experimentally determined field correlation and a standard adiabatic z-rotation pulse as a starting point for the iterative optimization procedure. The shape of the z-rotation RF pulse is manipulated to provide refocusing for the conditions given by the sample-, magnet-, and RF-coil geometry. (c) 2005 Elsevier Inc. All rights reserved.
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| 10. |
- Ulvenlund, S., et al.
(författare)
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Solid-state and diffusion NMR spectroscopy as applied to characterization of complex formulated products and biological materials
- 2016
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Ingår i: Advanced Materials - TechConnect Briefs 2016. - 9780997511703 ; 1, s. 304-307
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Konferensbidrag (refereegranskat)abstract
- Solid-state and diffusion NMR spectroscopy are versatile tools that allow for studies of both structure and dynamics of complex solid and semisolid materials. We have developed a suit of pulse sequences based on polarization transfer that is readily applied to studies of formulations and their interactions with biological systems. In the present paper, we illustrate its applicability by using an incompletely hydrated surfactant system (tetradecyl-maltoside, C14G2) and skin (stratum corneum, SC) as examples. In the former case, solid-state NMR has allowed us to study the dynamics of the system at the level of individual functional groups, and also to derive the surprisingly complex C14G2-H2O phase diagram at water contents <5%. For SC, NMR data has allowed us to study the effect of natural moisturizing factor (NMF) on the dynamics of its lipid and protein constituents. The results challenge the conventional view that NMF protects the skin from dryness by increasing its water content.
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