Software Simulation of Magnetic Resonance Imaging - Ca Da Alt N

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Real-time fMRI Biofeedback Targeting the Orbitofrontal Cortex

/ Aletras, Anthony; Arai, A E. In: Journal of Magnetic Resonance, Vol. 169, No. 2, 2004, p. 246-249 meta-DENSE complex acquisition for reduced intravoxel dephasing. Aletras, Anthony LU and Arai, A E In Journal of Magnetic Resonance 169 (2). p.246-249. Mark The resultant intravoxel dephasing is a classic T2*-shortening effect most prominent near larger veins and accentuated by use of GRE sequences with echo times (TEs) close to T2*. The effect scales linearly with field strength (Bo) and is the dominant mechanism for BOLD contrast at 1.5T. Each cylinder contributed to the intravoxel dephasing and associated signal loss occurring in the ROI ROI MGL decay on simulated and experimental images for the network of air-filled cylinders.

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Why study at Lund University In gradient-echo images, not in spin-echo images, these local fields cause intravoxel dephasing of the water signal of the surrounding tissue. This description of the contrast enhancement has been confirmed by a series of in vitro blood sample experiments and image simulations. Errors arise from intravoxel dephasing and the intravoxel asymmetry. The spectral leakage due to intravoxel dephasing is roughly 6-8% from one voxel to one of its nearest neighbors. Neighbors further away are influenced less significantly. The loss of localization due to intravoxel … The resultant intravoxel dephasing is a classic T2*-shortening effect most prominent near larger veins and accentuated by use of GRE sequences with echo times (TEs) close to T2*. The effect scales linearly with field strength (Bo) and is the dominant mechanism for BOLD contrast at 1.5T. In MRI, intravoxel dephasing causes signal loss in regions of magnetic field inhomogeneity and at interfaces of tissues having different magnetic susceptibilities.

Real-time fMRI Biofeedback Targeting the Orbitofrontal Cortex

Gradient-recalled echo sequences are par- ticularly prone to metallic artifact because of intravoxel dephasing [3] (Fig. the 180° refocusing pulse) and/or intravoxel dephasing (spins moving with different velocities due to turbulent or laminar flow acquire different phases) 1.

Software Simulation of Magnetic Resonance Imaging - Ca Da Alt N

Intravoxel dephasing

The main effect of such macroscopic field inhomogeneities is the intravoxel dephasing that can cause significant signal losses, mainly for inhomogeneities in the slice direction (see Section 2.2.1 and Figure 2.2.3), which is a particular problem in the human spinal cord (see Section 2.2.2 and Figure 2.2.10). Signal decay due to susceptibility-induced intravoxel dephasing on multiple air-filled cylinders: MRI simulations and experiments. De Guio F(1), Benoit-Cattin H, Davenel A. Author information: (1)Cemagref, Food Process Engineering Research Unit, 35 044, Rennes, France. francois.de-guio@cemagref.fr ‘‘intravoxel dephasing,’’ but also from incomplete refocus-phase-encoding direction shift the gradient echo along corre-ing of the slice-selection gradient. Moreover, while intra-sponding directions in k space. Fourier transformation results voxel dephasing originates from an increase in broadness of Experiments were performed with a 0.2 T magnet on a network of small interacting air-filled cylinders along with Magnetic resonance imaging (MRI) simulations integrating intravoxel dephasing.

Intravoxel dephasing

Spin echo methods refocus the static field heterogeneities, and therefore do not have signal dropout. The relationships between contrast, artifacts and field strength are summarized in Table 1. At this time, 7 Tand higher field magnets are not in wide-spreaduse Se hela listan på academic.oup.com This paper addresses one of the major problems in interventional magnetic resonance imaging (MRI): the visualization of interventional devices.
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Intravoxel dephasing

Aletras, Anthony LU and Arai, A E In Journal of Magnetic Resonance 169 (2). p.246-249.

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.
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Real-time fMRI Biofeedback Targeting the Orbitofrontal Cortex

The bright artery and MR vessel wall imaging refers to MRI techniques used to evaluate for disease within the walls of arteries, beyond the luminal abnormalities depicted on angiographic imaging.This can be used anywhere in the body but is particularly important intracranially in distinguishing between various causes of luminal stenosis such as intracranial atherosclerotic disease versus vasculitis. This happens because of intravoxel dephasing of the inflowing blood experiencing magnetic field inhomogeneities. The dephasing of spins leads to less signal within the vessel and an apparent increased stenosis. Turbulent flow also leads to rapid dephasing that cannot be corrected.