Real-time fMRI Biofeedback Targeting the Orbitofrontal Cortex

Journal of Magnetic Resonance - Research Outputs - Lund

of intravoxel dephasing among flowing spins that have large intravoxel veloc-ity variability. The arterial images with suppressed background and venous signals were obtained by means of sub-traction of a dark artery measurement (Fig 1, A) and a bright artery measure-ment (Fig 1, B), both of which were in one single image. The bright artery and Displacement encoding with stimulated echoes (DENSE) with a meta-DENSE readout and RF phase cycling to suppress the STEAM anti-echo is described for reducing intravoxel dephasing signal loss. This RF phase cycling scheme, when combined with existing meta-DENSE suppression of the T1 recovering signal, yields higher quality DENSE myocardial strain maps. Phantom and human images are provided to mechanism is intravoxel dephasing: Luminal blood contains spins travelingatvaryingvelocities(eg,duetolaminarflow).Betweenthe time of excitation and readout, these spins move through the mag-netic field gradients at different rates, resulting in intravoxel phase dispersion with signal loss.8 One may further exploit the intravoxel This paper addresses one of the major problems in interventional magnetic resonance imaging (MRI): the visualization of interventional devices.

The contrast-to-noiseratio (CNR) between CSF and the cerebellar peduncle, and the visibility of the cranial nerves and vertebrobasilar artery were signiﬁcantly improved on 3D images in 17 subjects. susceptibility, dipole effect, dipole inversion, intravoxel dephasing, nonlinear T2* magnitude image, T2* phase unwrapping, MRI transformations. INTRODUCTION. The concept of tomographic imaging refers to reproducing a digital image representation of object interior distribution (with respect to a physical property) and can be implemented by The strong effective intravoxel dephasing caused by magnetic microparticles has made them promising candidates for MR tracking and contrast enhancement. Magnetic particles with identical volumes and magnetic moments produce equal amounts of signal loss in MR images. However, distribution of smaller magnetic particles over a PURPOSE: In 3D gradient echo magnetic resonance imaging (MRI), strong field gradients B0macro are visually observed at air/tissue interfaces.

Individuell kartläggning av hjärnan, ett fmri-datasæt med hög

Översikt; Cite Bibtex Detaljer. Författare: Anthony Aletras; A E Arai; Externa organisationer: National Heart Lung and Blood Displacement encoding with stimulated echoes (DENSE) with a meta-DENSE readout and RF phase cycling to suppress the STEAM anti-echo is described for reducing intravoxel dephasing signal loss. Spin dephasing under nonlinear gradients: Implications for imaging and field mapping. Magnetic Resonance in Medicine, 2012.

Journal of Magnetic Resonance - Research Outputs - Lund

In MRI, intravoxel dephasing causes signal loss in regions of magnetic field inhomogeneity and at interfaces of tissues having different magnetic susceptibilities. In MRA, signal loss due to intravoxel dephasing also occurs when nuclei having different velocities are present in the same voxel. The cause of intravoxel dephasing is not yet well understood.

Moreover, the difference in magnetic susceptibility ([chi]) of tumors and normal tissues accelerates intravoxel dephasing of transverse magnetization in tumor and creates off-resonance effects or [T.sup.*sub.2] contrast, a combination of spin-spin relaxation ([T.sub.2]) and [B.sub.0] magnetic field inhomogeneity.
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This method is composed of two components: mapping of the internal gradient and design of the slice‐selective radiofrequency (RF) pulse. The RF pulse is designed with its phase response as the negative of the product of a chosen echo time and the At very low diffusion weighting the diffusion MRI signal is affected by intravoxel incoherent motion (IVIM) caused by dephasing of magnetization due to incoherent blood flow in capillaries or other sources of microcirculation.

Magnetic Resonance in Medicine.
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Individuell kartläggning av hjärnan, ett fmri-datasæt med hög

Fourier transformation results voxel dephasing originates from an increase in broadness of Efficient and Accurate Bloch-based Simulation of Intra-voxel Dephasing using Multiple Isochomats and Magnetization Spatial Gradients Zhipeng Cao 1, Christopher T. Sica, Giuseppe Carluccio 2, and Christopher M. Collins 1Radiology, The Pennsylvania State University, Hershey, PA, United States, 2Radiology, New York University, New York City, NY, United States Many different mechanisms have been found to influence intravoxel dephasing signal loss in stenotic jets including higher‐order motion, e.g., acceleration (11-14), alignment of the image plane with the jet (15, 16), voxel size and partial volume effects in voxels with large velocity distributions (10, 17-20) the user‐defined velocity encoding (Venc) , and turbulence imposing small velocity Materials and methods Experiments were performed with a 0.2T magnet on a network of small interacting air-filled cylinders along with Magnetic resonance imaging (MRI) simulations integrating intravoxel dephasing. Signal decay over echo time was assessed at different pixel sizes on real and simulated images. Read "Signal decay due to susceptibility-induced intravoxel dephasing on multiple air-filled cylinders: MRI simulations and experiments, Magnetic Resonance Materials in Physics, Biology and Medicine" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. 2008-06-25 These effects are negated by flow-related dephasing and are only seen well in short TE sequences.

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Real-time fMRI Biofeedback Targeting the Orbitofrontal Cortex

For voxels near metal or air/tissue boundaries, this can be considerable.

Software Simulation of Magnetic Resonance Imaging: Alt N, Ca Da

meta-DENSE complex acquisition for reduced intravoxel dephasing.

Read "Signal decay due to susceptibility-induced intravoxel dephasing on multiple air-filled cylinders: MRI simulations and experiments, Magnetic Resonance Materials in Physics, Biology and Medicine" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. 2008-06-25 These effects are negated by flow-related dephasing and are only seen well in short TE sequences. Intravoxel dephasing related to turbulence Accumulation of positive phase shift over the course of the scan Fat-saturation pulses as used in time-of-flight imaging Inflow of unsaturated blood into the meta-DENSE complex acquisition for reduced intravoxel dephasing. / Aletras, Anthony; Arai, A E. In: Journal of Magnetic Resonance, Vol. 169, No. 2, 2004, p. 246-249 Signal loss due to flow is induced via intravoxel dephasing which, according to Eq. 1, is dependent on velocity profile and m1. For a certain velocity profile, the flow suppression capability of FSD-preparation is determined by m1. Haacke et al.