The Experts below are selected from a list of 19179 Experts worldwide ranked by ideXlab platform
Timo Liimatainen - One of the best experts on this subject based on the ideXlab platform.
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the follow up of progressive hypertrophic cardiomyopathy using magnetic resonance Rotating Frame relaxation times
NMR in Biomedicine, 2018Co-Authors: Muhammad Arsalan Khan, Hanne Laakso, Svetlana Laidinen, Sanna Kettunen, Tommi Heikura, Seppo Ylaherttuala, Timo LiimatainenAbstract:Magnetic resonance Rotating Frame relaxation times are an alternative non-contrast agent choice for the diagnosis of chronic myocardial infarct. Fibrosis typically occurs in progressive hypertrophic cardiomyopathy. Fibrosis has been imaged in myocardial infarcted tissue using Rotating Frame relaxation times, which provides the possibility to follow up progressive cardiomyopathy without contrast agents. Mild and severe left ventricular hypertrophy were induced in mice by transverse aortic constriction, and the longitudinal Rotating Frame relaxation times (T1ρ ) and relaxation along the fictitious field (TRAFF2 , TRAFF3 ) were measured at 5, 10, 24, 62 and 89 days after transverse aortic constriction in vivo. Myocardial fibrosis was verified using Masson's trichrome staining. Increases in the relative relaxation time differences of T1ρ , together with TRAFF2 and TRAFF3 , between fibrotic and remote tissues over time were observed. Furthermore, TRAFF2 and TRAFF3 showed higher relaxation times overall in fibrotic tissue than T1ρ . Relaxation time differences were highly correlated with an excess of histologically verified fibrosis. We found that TRAFF2 and TRAFF3 are more sensitive than T1ρ to hypertrophic cardiomyopathy-related tissue changes and can serve as non-invasive diagnostic magnetic resonance imaging markers to follow up the mouse model of progressive hypertrophic cardiomyopathy.
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Rotating Frame relaxation during adiabatic pulses vs conventional spin lock simulations and experimental results at 4 t
Magnetic Resonance Imaging, 2009Co-Authors: Silvia Mangia, Timo Liimatainen, Michael Garwood, Shalom MichaeliAbstract:Abstract Spin relaxation taking place during radiofrequency (RF) irradiation can be assessed by measuring the longitudinal and transverse Rotating Frame relaxation rate constants (R1ρ and R2ρ). These relaxation parameters can be altered by utilizing different settings of the RF irradiation, thus providing a useful tool to generate contrast in MRI. In this work, we investigate the dependencies of R1ρ and R2ρ due to dipolar interactions and anisochronous exchange (i.e., exchange between spins with different chemical shift δω≠0) on the properties of conventional spin-lock and adiabatic pulses, with particular emphasis on the latter ones which were not fully described previously. The results of simulations based on relaxation theory provide a foundation for formulating practical considerations for in vivo applications of Rotating Frame relaxation methods. Rotating Frame relaxation measurements obtained from phantoms and from the human brain at 4 T are presented to confirm the theoretical predictions.
D. J. Pusiol - One of the best experts on this subject based on the ideXlab platform.
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Echo-planar Rotating-Frame imaging
Journal of Magnetic Resonance, 2003Co-Authors: F. Casanova, H. Robert, Josefina Perlo, D. J. PusiolAbstract:A new Rotating-Frame imaging method that produces a complete cross section of an object in a single experiment is reported. The echo planar Rotating Frame imaging (EPROFI) technique uses two perpendicular RF gradients for two-dimensional spatial encoding and fully exploits the formation of rotary echoes for fast sampling of spatial frequencies. The acquisition scheme yields the Fourier transform of the spin distribution on Cartesian coordinates for straightforward image reconstruction. Implementation of the technique on a low-field portable NMR probe is described and results are presented for test objects with different geometries.
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Improving resolution in fast Rotating-Frame experiments.
Journal of Magnetic Resonance, 2001Co-Authors: F. Casanova, H. Robert, D. J. PusiolAbstract:The rapid Rotating-Frame technique allows significant reduction in data-acquisition time compared with the two-dimensional method by stroboscopic observation of the nuclear magnetization during its evolution in the Rotating Frame. A onefold reduction in the dimensionality of the original Rotating-Frame experiment is achieved by using a train of strong radiofrequency pulses separated by short acquisition windows. The penalty for shortening experimental time is a reduction in spectral resolution compared with the two-dimensional method due to relaxation of transverse magnetization components during the observation windows. A variant of the rapid-Rotating Frame technique for improving spectral resolution based on undersampling and self-phase encoding is presented. An M-fold resolution improvement requires M experiments, thus, making possible a tradeoff between spectral resolution and experimental time. The technique was applied for spatial localization of quadrupole nuclei in powder solids, and resolution improvement is demonstrated on one- and two-dimensional NQR images.
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Phase-Modulated Rotating-Frame NQR Techniques for Spatial Encoding
Journal of Magnetic Resonance, 1999Co-Authors: F. Casanova, H. Robert, D. J. PusiolAbstract:Abstract The Rotating-Frame method of localization for spatially resolved spectroscopy and imaging in the pure quadrupole regime relies on a gradient B1 field in which spins experience a flip angle dependent on their position in the B1 field strength. So far, the techniques have been implemented as amplitude-modulated methods, i.e., the spatial nuclear quadrupole distribution is encoded in the amplitude of the free-induction decay signals. In this work, we describe the implementation of phase-modulated variants of both two-dimensional and rapid Rotating-Frame imaging techniques. The experiments are discussed for both single crystalline and powder samples. The phase-modulated experiment offers some advantages over the amplitude-encoding technique: It enables one to distinguish the sign of the spatial coordinate and the signal-to-noise ratio is higher than for the simplest amplitude-encoding method.
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Two-Dimensional Rotating-Frame NQR Imaging
Journal of Magnetic Resonance, 1997Co-Authors: H. Robert, D. J. PusiolAbstract:Abstract A new technique for two-dimensional Rotating-Frame nuclear-quadrupole-resonance imaging in powder or polycrystalline samples is reported. The bidimensional encoding procedure is based on the irradiation of the object by a sequence of pulsed orthogonal radiofrequency linear gradients. The spatial-density function, together with the spectroscopic information, is directly recorded in Cartesian coordinates. Several variants of the encoding procedure are discussed, and experimental results demonstrating the viability of the technique are given.
Shalom Michaeli - One of the best experts on this subject based on the ideXlab platform.
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Rotating Frame mri relaxations as markers of diffuse white matter abnormalities in multiple sclerosis
NeuroImage: Clinical, 2020Co-Authors: Pavel Filip, Alena Svatkova, Adam F Carpenter, Lynn E Eberly, Igor Nestrasil, Mikko J Nissi, Shalom Michaeli, Silvia MangiaAbstract:Even though MRI visualization of white matter lesions is pivotal for the diagnosis and management of multiple sclerosis (MS), the issue of detecting diffuse brain tissue damage beyond the apparent T2-hyperintense lesions continues to spark considerable interest. Motivated by the notion that Rotating Frame MRI methods are sensitive to slow motional regimes critical for tissue characterization, here we utilized novel imaging protocols of Rotating Frame MRI on a clinical 3 Tesla platform, including adiabatic longitudinal, T1ρ, and transverse, T2ρ, relaxation methods, and Relaxation Along a Fictitious Field (RAFF) in the Rotating Frame of rank 4 (RAFF4), in 10 relapsing-remitting multiple sclerosis patients and 10 sex- and age-matched healthy controls. T1ρ, T2ρ and RAFF4 relaxograms extracted from the whole white matter exhibited a significant shift towards longer relaxation time constants in MS patients as compared to controls. T1ρ and RAFF4 detected alterations even when considering only regions of normally appearing white matter (NAWM), while other MRI metrics such as T1w/T2w ratio and diffusion tensor imaging measures failed to find group differences. In addition, RAFF4, T2ρ and, to a lesser extent, T1ρ showed differences in subcortical grey matter structures, mainly hippocampus, whereas no functional changes in this region were detected in resting-state functional MRI metrics. We conclude that Rotating Frame MRI techniques are exceptionally sensitive methods for the detection of subtle abnormalities not only in NAWM, but also in deep grey matter in MS, where they surpass even highly sensitive measures of functional changes, which are often suggested to precede detectable structural alterations. Such abnormalities are consistent with a wide spectrum of different, but interconnected pathological features of MS, including the loss of neuronal cells and their axons, decreased levels of myelin even in NAWM, and altered iron content.
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Rotating Frame relaxation during adiabatic pulses vs conventional spin lock simulations and experimental results at 4 t
Magnetic Resonance Imaging, 2009Co-Authors: Silvia Mangia, Timo Liimatainen, Michael Garwood, Shalom MichaeliAbstract:Abstract Spin relaxation taking place during radiofrequency (RF) irradiation can be assessed by measuring the longitudinal and transverse Rotating Frame relaxation rate constants (R1ρ and R2ρ). These relaxation parameters can be altered by utilizing different settings of the RF irradiation, thus providing a useful tool to generate contrast in MRI. In this work, we investigate the dependencies of R1ρ and R2ρ due to dipolar interactions and anisochronous exchange (i.e., exchange between spins with different chemical shift δω≠0) on the properties of conventional spin-lock and adiabatic pulses, with particular emphasis on the latter ones which were not fully described previously. The results of simulations based on relaxation theory provide a foundation for formulating practical considerations for in vivo applications of Rotating Frame relaxation methods. Rotating Frame relaxation measurements obtained from phantoms and from the human brain at 4 T are presented to confirm the theoretical predictions.
Yusuf Yayli - One of the best experts on this subject based on the ideXlab platform.
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the fermi walker derivative and non Rotating Frame in dual space
Advances in Applied Clifford Algebras, 2018Co-Authors: Tevfik şahin, Fatma Karakuş, Yusuf YayliAbstract:In this study, we defined Fermi–Walker derivative in dual space $$\mathbb {D}^3$$ . Fermi–Walker transport, non-Rotating Frame and Fermi–Walker termed Darboux vector by using Fermi–Walker derivative are given in dual space $$\mathbb {D}^3$$ . Being conditions of Fermi–Walker transport and non-Rotating Frame are investigated along any dual curve for dual Frenet Frame, dual Darboux Frame and dual Bishop Frame.
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The Fermi–Walker Derivative and Non-Rotating Frame in Dual Space
Advances in Applied Clifford Algebras, 2018Co-Authors: Tevfik şahin, Fatma Karakuş, Yusuf YayliAbstract:In this study, we defined Fermi–Walker derivative in dual space $$\mathbb {D}^3$$ . Fermi–Walker transport, non-Rotating Frame and Fermi–Walker termed Darboux vector by using Fermi–Walker derivative are given in dual space $$\mathbb {D}^3$$ . Being conditions of Fermi–Walker transport and non-Rotating Frame are investigated along any dual curve for dual Frenet Frame, dual Darboux Frame and dual Bishop Frame.
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Generalized Fermi–Walker derivative and non-Rotating Frame
International Journal of Geometric Methods in Modern Physics, 2017Co-Authors: Ayşenur Uçar, Fatma Karakuş, Yusuf YayliAbstract:In this paper, generalized Fermi–Walker derivative, generalized Fermi–Walker parallelism and generalized non-Rotating Frame concepts are given for Frenet Frame, Darboux Frame and Bishop Frame for any curve in Euclidean space. Being generalized, non-Rotating Frame conditions are analyzed for each Frames along the curve. Then we show that Frenet and Darboux Frames are generalized non-Rotating Frames along all curves and also Bishop Frame is generalized non-Rotating Frame along planar curves in Euclidean space.
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GENERALIZED FERMI-WALKER DERIVATIVE AND NON-Rotating Frame
International Journal of Geometric Methods in Modern Physics, 2017Co-Authors: Ayşenur Uçar, Fatma Karakuş, Yusuf YayliAbstract:In this paper, generalized Fermi–Walker derivative, generalized Fermi–Walker parallelism and generalized non-Rotating Frame concepts are given for Frenet Frame, Darboux Frame and Bishop Frame for a...
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ON THE FERMI–WALKER DERIVATIVE AND NON-Rotating Frame
International Journal of Geometric Methods in Modern Physics, 2012Co-Authors: Fatma Karakuş, Yusuf YayliAbstract:In this study Fermi–Walker derivative and according to the derivative Fermi–Walker parallelism and non-Rotating Frame concepts are given for some Frames. First, we get the Frenet Frame, the Darboux Frame, the Bishop Frame for any curve in Euclid space. Fermi–Walker derivative and non-Rotating Frame being conditions are analyzed for each of the Frames along the curve. Then we proved the Frenet Frame is non-Rotating Frame along the plane curves. Darboux Frame which is a non-Rotating Frame along the line of curvature. Then we proved the Bishop Frame is a non-Rotating Frame along the all curves.
Silvia Mangia - One of the best experts on this subject based on the ideXlab platform.
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Rotating Frame mri relaxations as markers of diffuse white matter abnormalities in multiple sclerosis
NeuroImage: Clinical, 2020Co-Authors: Pavel Filip, Alena Svatkova, Adam F Carpenter, Lynn E Eberly, Igor Nestrasil, Mikko J Nissi, Shalom Michaeli, Silvia MangiaAbstract:Even though MRI visualization of white matter lesions is pivotal for the diagnosis and management of multiple sclerosis (MS), the issue of detecting diffuse brain tissue damage beyond the apparent T2-hyperintense lesions continues to spark considerable interest. Motivated by the notion that Rotating Frame MRI methods are sensitive to slow motional regimes critical for tissue characterization, here we utilized novel imaging protocols of Rotating Frame MRI on a clinical 3 Tesla platform, including adiabatic longitudinal, T1ρ, and transverse, T2ρ, relaxation methods, and Relaxation Along a Fictitious Field (RAFF) in the Rotating Frame of rank 4 (RAFF4), in 10 relapsing-remitting multiple sclerosis patients and 10 sex- and age-matched healthy controls. T1ρ, T2ρ and RAFF4 relaxograms extracted from the whole white matter exhibited a significant shift towards longer relaxation time constants in MS patients as compared to controls. T1ρ and RAFF4 detected alterations even when considering only regions of normally appearing white matter (NAWM), while other MRI metrics such as T1w/T2w ratio and diffusion tensor imaging measures failed to find group differences. In addition, RAFF4, T2ρ and, to a lesser extent, T1ρ showed differences in subcortical grey matter structures, mainly hippocampus, whereas no functional changes in this region were detected in resting-state functional MRI metrics. We conclude that Rotating Frame MRI techniques are exceptionally sensitive methods for the detection of subtle abnormalities not only in NAWM, but also in deep grey matter in MS, where they surpass even highly sensitive measures of functional changes, which are often suggested to precede detectable structural alterations. Such abnormalities are consistent with a wide spectrum of different, but interconnected pathological features of MS, including the loss of neuronal cells and their axons, decreased levels of myelin even in NAWM, and altered iron content.
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Rotating Frame relaxation during adiabatic pulses vs conventional spin lock simulations and experimental results at 4 t
Magnetic Resonance Imaging, 2009Co-Authors: Silvia Mangia, Timo Liimatainen, Michael Garwood, Shalom MichaeliAbstract:Abstract Spin relaxation taking place during radiofrequency (RF) irradiation can be assessed by measuring the longitudinal and transverse Rotating Frame relaxation rate constants (R1ρ and R2ρ). These relaxation parameters can be altered by utilizing different settings of the RF irradiation, thus providing a useful tool to generate contrast in MRI. In this work, we investigate the dependencies of R1ρ and R2ρ due to dipolar interactions and anisochronous exchange (i.e., exchange between spins with different chemical shift δω≠0) on the properties of conventional spin-lock and adiabatic pulses, with particular emphasis on the latter ones which were not fully described previously. The results of simulations based on relaxation theory provide a foundation for formulating practical considerations for in vivo applications of Rotating Frame relaxation methods. Rotating Frame relaxation measurements obtained from phantoms and from the human brain at 4 T are presented to confirm the theoretical predictions.
