Frahm, J., Merboldt, K. D., & Haenicke, W. (1995). The effects of intravoxel dephasing and incomplete slice refocusing on susceptibility contrast in gradient-echo MRI.

intravoxel dephasing and inaccurate flow quantification using conventional PC MRI tec hniques. Disturbed, swirling, and turbulent and chaotic flows may also be observed at bifurcations, branch points, and other regions of the arterial tree where blood flow is altered. In turn, these areas are more prone to atherosclerosis and narrowing in vessels.

the variation in phase across the voxel is reduced, which reduces intravoxel dephasing. Prior to MR angiography (MRA), GRE sequences were commonly used to PC methods are equally sensitive to intravoxel dephasing as TOF techniques. 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.

Intravoxel dephasing mri

FOV. Field of view. RO ated with intravoxel dephasing that over the course of a. 18 Oct 2010 Summary: Since the first 3 Tesla (3T) magnetic resonance imaging Decreases in voxel size can also limit the amount of intravoxel dephasing. The large blood signal is minimally affected by intravoxel dephasing, which is typically caused by complex flow and susceptibility variations. Because the contrast-.

In particular, this article attempts to describe the methodology used to generate Figure 9 of [1]. For simplicity, assume a two-dimensional problem. Part 2 of 4The individual magnetization vectors start to de-phase because of interaction and magnet inhomegeneity Between the time of excitation and readout, these spins move through the magnetic field gradients at different rates, resulting in intravoxel phase dispersion with signal loss.

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 slice after the initial 90-degree pulse Flow-related enhancement is caused by 'naive' blood entering the slice.

In particular, this article attempts to describe the methodology used to generate Figure 9 of [1]. For simplicity, assume a two-dimensional problem.

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 slice after the initial 90-degree pulse Flow-related enhancement is caused by 'naive' blood entering the slice.

MRI chapter 6 flow phenomena study guide by paige_bazzrea includes 25 questions covering vocabulary, terms and more. Quizlet flashcards, activities and games help you improve your grades. In MRI, particularly turbulent blood ﬂow gives rise to intravoxel dephasing, where spins within a voxel have accrued different amounts of phase leading to reduced M xy magni-tude. However, it is important to note that if there is homog-enous ﬂow, the phase of all spins in a voxel changes by the Objective Characterization of magnetic susceptibility artefacts with assessment of the gradient-echo signal decay function of echo time, pixel size, and object geometry in the case of air-filled cylinders embedded in water. Materials and methods 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.

directions result in more rapid dephasing and signal loss termed “intravoxel dephasing.” A commonly encountered CSF flow artifact is the signal void in the dorsal subarachnoid space on sagittal T2-weighted images of the thoracic spine (Fig.
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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 [25]. The effects of intravoxel dephasing and incomplete slice refocusing on susceptibility contrast in gradient-echo MRI. Journal of Magnetic Resonance Series B, 109 (2), 234-237. Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-026C-B By decomposing the T2 * MRI technology further into 2 steps, 6 3D convolution for tissue magnetization and intravoxel dephasing for T2 * image formation, we will show that the T2 * MRI nonlinearity is largely due to the T2 * magnitude and phase calculations from a T2 * complex image.

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.
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Materials and methods Experiments were performed with Keywords Magnetic susceptibility · Intravoxel dephasing · a 0.2 T magnet on a network of small interacting air-ﬁlled Signal loss · Artefacts · MRI simulation · cylinders along with Magnetic resonance imaging (MRI) Field inhomogeneity simulations integrating intravoxel dephasing.

2004-08-01 · Intravoxel dephasing signal loss is less but still not acceptable for this healthy volunteer. Note that adipose tissue still is plagued by tagging artifacts due to its short T 1 . (C) Further lowering of the encoding gradient moment (4.0 mm/π) results in significant improvement in terms of reduced signal loss in the myocardium due to intravoxel dephasing. Politics, Philosophy, Language and Communication Studies. Graduate School. Medicine and Health Sciences Steady-state free precession (SSFP) imaging is a magnetic resonance imaging (MRI) sequence which uses steady states of magnetizations. In general, SSFP MRI sequences are based on a (low flip angle) gradient echo MRI sequence with a short repetition time which in its generic form has been described as the FLASH MRI technique.