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

meta-DENSE complex acquisition for reduced intravoxel dephasing. Research output: Contribution to journal › Article. Overview; Cite BibTeX Details. Authors: Anthony Aletras; A E Arai; External organisations: National Heart Lung and Blood Institute; Research areas and keywords

even echo rephasing, gradient moment nulling, spatial presaturation. 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. magnetization) and the complex multivoxel MR image (by intravoxel dephasing). Given the predefined susceptibility source and the calculated complex MR image, we compare the MR magnitude (phase, respectively) image with the predefined susceptibility source (the … intravoxel dephasing and amplitude of the section-selecting gradient. 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.

• Increasing the Gradient moment nulling is a technique used to reduce flow artifacts in our image and intravoxel dephasing. It is also a technique used in bright blood imaging. The large blood signal is minimally affected by intravoxel dephasing, which is typically caused by complex flow and susceptibility variations. Because the contrast-. Jul 14, 2013 The most relevant include: (i) complex flow patterns with consequent intravoxel dephasing and underestimation in velocity measurement,7,13 @article{323d424c14ab4cd284ed0796dbb9850f,. title = "meta-DENSE complex acquisition for reduced intravoxel dephasing.",. author = "Anthony Aletras and av P Dyverfeldt · 2010 · Citerat av 6 — Quantification of Intravoxel Velocity Standard Deviation and Turbulence Intensity by necessary to obtain a dephasing that results in a detectable signal loss.

Intravoxel Dephasing due to Wave Gradients. This article assumes prior knowledge of Wave-CAIPI[1]. In particular, this article attempts to describe the methodology used to generate Figure 9 of [1]. For simplicity, assume a two-dimensional problem.

Several methods have been devel- 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) (21), and turbulence imposing small velocity fluctuations superimposed on the principal velocity (22). Skip to main content. swedish website; Menu.

Through-slice dephasing is highly effective in suppressing eddy current induced artifacts in bSSFP imaging. Considering these artifacts appear substantial in Cart-GR and random PE scans, they are most likely caused by the zero order (spatially independent) EC field yielding an off-resonance shift over time.

During the last decade modern scanners have overcome these limitations making bSSFP a viable and useful sequence on most mid- and high-field systems. Start Forskningsoutput meta-DENSE complex acquisition for reduced intravoxel dephas meta-DENSE complex acquisition for reduced intravoxel dephasing. 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.

intra-voxel dephasing, at least three methods have been presented previously: Method 1 (Isochromat Summation, IS) numerical methods populating the input model voxel with numerous isochromats (magnetization vectors) and thus effectively increasing the model resolution [3], 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. Signal decay over echo time was assessed at different pixel sizes on real and simulated images. These symmetrical gradient lobes have the sole purpose of enhancing dephasing of spins, thereby accelerating intravoxel incoherent motion (IVIM) signal loss. Dephasing is proportional to the square of the time (diffusion time) during which the gradients are switched on and the strength of the applied gradient field. Another cause of dephasing is intravoxel dephasing. Because of laminar flow, different velocities may exist within a voxel, thus leading to phase dispersion (incoherence) and signal loss.
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Todd Constable. PDF. Download Free PDF. Free PDF. Download with Google Download with Facebook. or. Create a free account to download. PDF. PDF. susceptibility, dipole effect, dipole inversion, intravoxel dephasing, nonlinear T2* magnitude image, T2* phase unwrapping, MRI transformations.

We show that intravoxel gradient dephasing, which is normally associated only with signal loss, can distort phase evolution and affect a voxel’s apparent frequency. In Section III, we demonstrate these distortions experimentally, comparing gradient maps taken at different slice thicknesses and offsets, which show good agreement with the analytical expression. Intravoxel dephasing could occur if the velocity distribution of the spins, due to in-plane motion, is too large.
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All spins are completely in phase at the instant of the spin echo, but immediately begin to dephase at a rate proportional to the amount of magnetic field inhomogeneity within the voxel. For voxels near metal or air/tissue boundaries, this can be considerable.

In gradient-echo images, not in spin-echo images, these local fields cause intravoxel dephasing of the water signal of the surrounding tissue. We show that intravoxel gradient dephasing, which is normally associated only with signal loss, can distort phase evolution and affect a voxel’s apparent frequency. In Section III, we demonstrate these distortions experimentally, comparing gradient maps taken at different slice thicknesses and offsets, which show good agreement with the analytical expression.