The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Lambertus W. Bartels - One of the best experts on this subject based on the ideXlab platform.
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Temperature dependence of the magnetic Volume Susceptibility of human breast fat tissue: an NMR study
Magnetic Resonance Materials in Physics Biology and Medicine, 2012Co-Authors: Sara M. Sprinkhuizen, Chris J. G. Bakker, Johannes H. Ippel, Rolf Boelens, Max A. Viergever, Lambertus W. BartelsAbstract:Object Proton resonance frequency shift (PRFS)-based MR thermometry (MRT) is hampered by heat-induced Susceptibility changes when applied in tissues containing fat, e.g., the human breast. In order to assess the impact of fat Susceptibility changes on PRFS-based MRT during thermal therapy in the human breast, reliable knowledge of the temperature dependence of the magnetic Volume Susceptibility of fat, dχ_fat/d T , is a prerequisite. In this work we have measured dχ_fat/d T of human breast fat tissue, using a double-reference method to ensure invariance to temperature-induced changes in the proton electron screening constant. Materials and methods Ex vivo measurements were taken on a 14.1 T five mm narrow bore NMR spectrometer. Breast fat tissue samples were collected from six subjects, directly postmortem. The Susceptibility was measured over a temperature range from 24°C to 65°C. Results A linear behavior of the Susceptibility over temperature was observed for all samples. The resulting dχ_fat/d T of human breast fat ranged between 0.0039 and 0.0076 ppm/°C. Conclusion It is concluded that the impact of heat-induced Susceptibility changes of fat during thermal therapy in the breast may not be neglected.
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Temperature-induced tissue Susceptibility changes lead to significant temperature errors in PRFS-based MR thermometry during thermal interventions.
Magnetic resonance in medicine, 2010Co-Authors: Sara M. Sprinkhuizen, Chris J. G. Bakker, Max A. Viergever, Maurits K. Konings, Martijn J. Van Der Bom, Lambertus W. BartelsAbstract:Proton resonance frequency shift-based MR thermometry (MRT) is hampered by temporal magnetic field changes. Temporal changes in the magnetic Susceptibility distribution lead to nonlocal field changes and are, therefore, a possible source of errors. The magnetic Volume Susceptibility of tissue is temperature dependent. For water-like tissues, this dependency is in the order of 0.002 ppm/°C. For fat, it is in the same order of magnitude as the temperature dependence of the proton electron screening constant of water (0.01 ppm/°C). For this reason, proton resonance frequency shift-based MR thermometry in fatty tissues, like the human breast, is expected to be prone to errors. We aimed to quantify the influence of the temperature dependence of the Susceptibility on proton resonance frequency shift-based MR thermometry. Heating experiments were performed in a controlled phantom set-up to show the impact of temperature-induced Susceptibility changes on actual proton resonance frequency shift-based temperature maps. To study the implications for a clinical case, simulations were performed in a 3D breast model. Temperature errors were quantified by computation of magnetic field changes in the glandular tissue, resulting from Susceptibility changes in a thermally heated region. The results of the experiments and simulations showed that the temperature-induced Susceptibility changes of water and fat lead to significant errors in proton resonance frequency shift-based MR thermometry.
Chris J. G. Bakker - One of the best experts on this subject based on the ideXlab platform.
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Temperature dependence of the magnetic Volume Susceptibility of human breast fat tissue: an NMR study
Magnetic Resonance Materials in Physics Biology and Medicine, 2012Co-Authors: Sara M. Sprinkhuizen, Chris J. G. Bakker, Johannes H. Ippel, Rolf Boelens, Max A. Viergever, Lambertus W. BartelsAbstract:Object Proton resonance frequency shift (PRFS)-based MR thermometry (MRT) is hampered by heat-induced Susceptibility changes when applied in tissues containing fat, e.g., the human breast. In order to assess the impact of fat Susceptibility changes on PRFS-based MRT during thermal therapy in the human breast, reliable knowledge of the temperature dependence of the magnetic Volume Susceptibility of fat, dχ_fat/d T , is a prerequisite. In this work we have measured dχ_fat/d T of human breast fat tissue, using a double-reference method to ensure invariance to temperature-induced changes in the proton electron screening constant. Materials and methods Ex vivo measurements were taken on a 14.1 T five mm narrow bore NMR spectrometer. Breast fat tissue samples were collected from six subjects, directly postmortem. The Susceptibility was measured over a temperature range from 24°C to 65°C. Results A linear behavior of the Susceptibility over temperature was observed for all samples. The resulting dχ_fat/d T of human breast fat ranged between 0.0039 and 0.0076 ppm/°C. Conclusion It is concluded that the impact of heat-induced Susceptibility changes of fat during thermal therapy in the breast may not be neglected.
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Temperature-induced tissue Susceptibility changes lead to significant temperature errors in PRFS-based MR thermometry during thermal interventions.
Magnetic resonance in medicine, 2010Co-Authors: Sara M. Sprinkhuizen, Chris J. G. Bakker, Max A. Viergever, Maurits K. Konings, Martijn J. Van Der Bom, Lambertus W. BartelsAbstract:Proton resonance frequency shift-based MR thermometry (MRT) is hampered by temporal magnetic field changes. Temporal changes in the magnetic Susceptibility distribution lead to nonlocal field changes and are, therefore, a possible source of errors. The magnetic Volume Susceptibility of tissue is temperature dependent. For water-like tissues, this dependency is in the order of 0.002 ppm/°C. For fat, it is in the same order of magnitude as the temperature dependence of the proton electron screening constant of water (0.01 ppm/°C). For this reason, proton resonance frequency shift-based MR thermometry in fatty tissues, like the human breast, is expected to be prone to errors. We aimed to quantify the influence of the temperature dependence of the Susceptibility on proton resonance frequency shift-based MR thermometry. Heating experiments were performed in a controlled phantom set-up to show the impact of temperature-induced Susceptibility changes on actual proton resonance frequency shift-based temperature maps. To study the implications for a clinical case, simulations were performed in a 3D breast model. Temperature errors were quantified by computation of magnetic field changes in the glandular tissue, resulting from Susceptibility changes in a thermally heated region. The results of the experiments and simulations showed that the temperature-induced Susceptibility changes of water and fat lead to significant errors in proton resonance frequency shift-based MR thermometry.
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Spectral characterization of local magnetic field inhomogeneities.
Physics in medicine and biology, 2005Co-Authors: Jan-henry Seppenwoolde, Mathilda Van Zijtveld, Chris J. G. BakkerAbstract:The purpose of this study was the characterization of local magnetic Susceptibility deviations by spectral analysis of their induced magnetic field inhomogeneities. Magnetic resonance spectra and related signal decay curves of local Susceptibility deviations were simulated for different Volume fractions and compositions of the object within the VOI. The size or composition of the object was varied at constant Volume fraction, constant object size, or at constant 'magnetic strength' (defined as the product of the Volume and the Volume Susceptibility of the object). Experimental spectra were acquired for individual metal spherical particles and a spherical air cavity. Where possible, spectra were used to characterize objects in terms of Volume and composition. By simulations, a numerical relation was determined between the spectral broadening and the object's Volume and composition. Comparison of spectra for various spherical objects showed the possibility of characterization with respect to size and composition. Experimental results confirmed the numerical results to a large extent, although the characterization was compromised by background signal decay, low Volume fractions and limitations in signal-to-noise. In conclusion, spectral description of the field inhomogeneities related to small objects allows characterization of such objects with respect to size and composition. Practical applicability of the simulation results depends on background signal decay and Volume fraction of the object.
Sara M. Sprinkhuizen - One of the best experts on this subject based on the ideXlab platform.
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Temperature dependence of the magnetic Volume Susceptibility of human breast fat tissue: an NMR study
Magnetic Resonance Materials in Physics Biology and Medicine, 2012Co-Authors: Sara M. Sprinkhuizen, Chris J. G. Bakker, Johannes H. Ippel, Rolf Boelens, Max A. Viergever, Lambertus W. BartelsAbstract:Object Proton resonance frequency shift (PRFS)-based MR thermometry (MRT) is hampered by heat-induced Susceptibility changes when applied in tissues containing fat, e.g., the human breast. In order to assess the impact of fat Susceptibility changes on PRFS-based MRT during thermal therapy in the human breast, reliable knowledge of the temperature dependence of the magnetic Volume Susceptibility of fat, dχ_fat/d T , is a prerequisite. In this work we have measured dχ_fat/d T of human breast fat tissue, using a double-reference method to ensure invariance to temperature-induced changes in the proton electron screening constant. Materials and methods Ex vivo measurements were taken on a 14.1 T five mm narrow bore NMR spectrometer. Breast fat tissue samples were collected from six subjects, directly postmortem. The Susceptibility was measured over a temperature range from 24°C to 65°C. Results A linear behavior of the Susceptibility over temperature was observed for all samples. The resulting dχ_fat/d T of human breast fat ranged between 0.0039 and 0.0076 ppm/°C. Conclusion It is concluded that the impact of heat-induced Susceptibility changes of fat during thermal therapy in the breast may not be neglected.
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Temperature-induced tissue Susceptibility changes lead to significant temperature errors in PRFS-based MR thermometry during thermal interventions.
Magnetic resonance in medicine, 2010Co-Authors: Sara M. Sprinkhuizen, Chris J. G. Bakker, Max A. Viergever, Maurits K. Konings, Martijn J. Van Der Bom, Lambertus W. BartelsAbstract:Proton resonance frequency shift-based MR thermometry (MRT) is hampered by temporal magnetic field changes. Temporal changes in the magnetic Susceptibility distribution lead to nonlocal field changes and are, therefore, a possible source of errors. The magnetic Volume Susceptibility of tissue is temperature dependent. For water-like tissues, this dependency is in the order of 0.002 ppm/°C. For fat, it is in the same order of magnitude as the temperature dependence of the proton electron screening constant of water (0.01 ppm/°C). For this reason, proton resonance frequency shift-based MR thermometry in fatty tissues, like the human breast, is expected to be prone to errors. We aimed to quantify the influence of the temperature dependence of the Susceptibility on proton resonance frequency shift-based MR thermometry. Heating experiments were performed in a controlled phantom set-up to show the impact of temperature-induced Susceptibility changes on actual proton resonance frequency shift-based temperature maps. To study the implications for a clinical case, simulations were performed in a 3D breast model. Temperature errors were quantified by computation of magnetic field changes in the glandular tissue, resulting from Susceptibility changes in a thermally heated region. The results of the experiments and simulations showed that the temperature-induced Susceptibility changes of water and fat lead to significant errors in proton resonance frequency shift-based MR thermometry.
Leo Van Wüllen - One of the best experts on this subject based on the ideXlab platform.
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Anomalous $^{13}$C isotope effect in the quasi one-dimensional superconductor Sc$_3$CoC$_4$
arXiv: Superconductivity, 2017Co-Authors: Christof D. Haas, Georg Eickerling, Ernst-wilhelm Scheidt, Dominik Schmitz, Daniel Eklöf, Jan Gerrit Schiffmann, Leo Van Wüllen, Anton Jesche, Wolfgang SchererAbstract:The substitution series of the quasi one-dimensional superconductor Sc$_3$Co($^{12}$C$_{1-x}$$^{13}$C$_x$)$_4$ with $x$ = 0 $-$ 1 was synthesized by arc melting. The high sample homogeneity is confirmed by powder X-ray diffraction and $^{13}$C solid-state NMR spectroscopy. An anomalous large $^{12}$C/$^{13}$C isotope shift of the superconducting onset temperature, $T_{\rm c}^{\rm onset}$, is observed in the temperature dependent Volume Susceptibility, ${\chi}$($T$), and the electrical resistivity, ${\rho}$($T$), of the polycrystalline samples. The obtained isotope coefficient, ${\alpha}$ > 6, represents the highest positive value observed so far.
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Unusually large $^{12}$C/$^{13}$C carbon isotope effect in the quasi one-dimensional superconductor Sc$_3$CoC$_4$
2017Co-Authors: Christof D. Haas, Georg Eickerling, Ernst-wilhelm Scheidt, Dominik Schmitz, Daniel Eklöf, Jan Gerrit Schiffmann, Jian Lyu, Junying Shen, Rolf Walter Lortz, Leo Van WüllenAbstract:The substitution series of the quasi one-dimensional superconductor Sc$_3$Co($^{12}$C$_{1-x}$$^{13}$C$_x$)$_4$ with $x$ = 0 $-$ 1 was synthesized by arc melting. The sample homogeneity is confirmed by powder X-ray diffraction and $^{13}$C solid-state NMR spectroscopy. An unusually large $^{12}$C/$^{13}$C carbon isotope shift of the superconducting onset temperature, $T_{\rm c}^{\rm onset}$, is observed in the temperature dependent Volume Susceptibility, ${\chi}$($T$), and the electrical resistivity, ${\rho}$($T$), of poly (pc)- and single crystalline (sc) samples. The obtained isotope coefficients, ${\alpha_{\chi,pc}}$ = 6.2(7), ${\alpha_{\rho,pc}}$ = 7.5(6) and ${\alpha_{\rho,sc}}$ = 7.0(6), represent the highest positive values observed so far.
Felix W Wehrli - One of the best experts on this subject based on the ideXlab platform.
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investigating the magnetic Susceptibility properties of fresh human blood for noninvasive oxygen saturation quantification
Magnetic Resonance in Medicine, 2012Co-Authors: Varsha Jain, Osheiza Abdulmalik, Kathleen J Propert, Felix W WehrliAbstract:Quantification of blood oxygen saturation on the basis of a measurement of its magnetic Susceptibility demands knowledge of the difference in Volume Susceptibility between fully oxygenated and fully deoxygenated blood (Δχdo). However, two very different values of Δχdo are currently in use. In this work we measured Δχdo as well as the Susceptibility of oxygenated blood relative to water, Δχoxy, by MR susceptometry in samples of freshly drawn human blood oxygenated to various levels, from 6 to 98% as determined by blood gas analysis. Regression analysis yielded 0.273 ± 0.006 and −0.008 ± 0.003 ppm (cgs) respectively, for Δχdo and Δχoxy, in excellent agreement with previous work by Spees et al. (Magn Reson Med 2001;45:533–542). Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
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magnetic Susceptibility measurement of insoluble solids by nmr magnetic Susceptibility of bone
Magnetic Resonance in Medicine, 1997Co-Authors: Jeffrey A Hopkins, Felix W WehrliAbstract:Measurements of the Volume magnetic Susceptibility of solids using the classical Gouy balance approach are hampered by variations in apparent density of the packed powder. In this paper a quantitative NMR measurement of the Volume magnetic Susceptibility of powdered solids is described and the Volume Susceptibility of bone is reported. The technique is based on the measurement of changes in incremental linewidth (1/πT2′) induced in a marker fluid whose Susceptibility can be predictably modified by changing the composition, such as by addition of a soluble diamagnetic compound. The spectroscopic linewidth of the marker fluid is determined by the Susceptibility difference between the fluid and the suspended solid. Changes in the linewidth are accompanied by bulk magnetic Susceptibility induced frequency shifts in the fluid resonance. Correlating the two dependencies allows measurement of the absolute Volume Susceptibility of the solid. The Susceptibility of bovine rib bone was found to be −0.90 ± 0.02 × − 10−6 (CGS) confirming previous estimates which suggested bone to be more diamagnetic than the marrow constituents. Knowledge of the Susceptibility of bone is relevant in view of the growing interest in MRI osteodensitometric techniques.
