Measurement of Flow with NMR Imaging Using a Gradient Pulse and Phase Difference Technique

Bryant, DJ; Ja, Payne; Firmin, David N.; Db, Longmore

doi:10.1097/00004728-198408000-00002

Cited by 512 publications

(214 citation statements)

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“…Magnetic resonance imaging (MRI) has also been used to measure flow through velocity-encoded phasecontrast (PC) techniques (8)(9)(10). The method requires two acquisitions with velocity-compensated and velocityencoding gradients to assess through-plane flow perpendicular to the imaging section.…”

Section: Introductionmentioning

confidence: 99%

Real-time magnetic resonance imaging of deep venous flow during muscular exercise—preliminary experience

Joseph

Merboldt

Voit

et al. 2016

Cardiovasc. Diagn. Ther.

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Background: The accurate assessment of peripheral venous flow is important for the early diagnosis and treatment of disorders such as deep-vein thrombosis (DVT) which is a major cause of post-thrombotic syndrome or even death due to pulmonary embolism. The aim of this work is to quantitatively determine blood flow in deep veins during rest and muscular exercise using a novel real-time magnetic resonance imaging (MRI) method for velocity-encoded phase-contrast (PC) MRI at high spatiotemporal resolution.

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Section: Introductionmentioning

confidence: 99%

Real-time magnetic resonance imaging of deep venous flow during muscular exercise—preliminary experience

Joseph

Merboldt

Voit

et al. 2016

Cardiovasc. Diagn. Ther.

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“…A large variety of NMRI pulse sequences is aimed at determining local flow velocities and transport properties [e.g., Watson and Chang, 1997]. Since our measurements are not limited by the acquisition time but require a very high spatial resolution and the determination of the velocity fields at high accuracy and resolution, we opted for a classical phase-imaging approach [e.g., Moran, 1982;Bryant et al, 1984], that is, twoand three-dimensional flow-encoded spin-echo pulse sequences. The detailed three-dimensional (3-D) pulse sequence is presented in Figure 2.…”

Section: Introductionmentioning

confidence: 99%

Investigation of flow in water‐saturated rock fractures using nuclear magnetic resonance imaging (NMRI)

Dijk¹,

Berkowitz²,

Bendel³

1999

Water Resources Research

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Abstract. The application of nuclear magnetic resonance imaging (NMRI) to the direct three-dimensional measurement of flow in rough-walled water-saturated rock fractures is presented for the first time. The study demonstrates the abilities of NMRI to noninvasively measure rock-water interfaces and water flow velocities in these fractures and investigates the effects of wall morphology on flow patterns inside a typical rock fracture. Two-and three-dimensional flow-encoded spin-echo pulse sequences were applied. The stability and reproducibility of the water flow patterns were confirmed by analyzing two-dimensional velocity images. A variety of geometrical and hydraulic features were determined from three-dimensional velocity images, including the rock-water interfaces, the fracture aperture distribution, and the critical aperture path; velocity profiles and volumetric flow rates; flow and stagnant regions; and the critical velocity path. In particular, the effects of a sharp step discontinuity of the fracture walls and the applicability of the cubic law were examined. As a result of the complex three-dimensional geometry, velocity profiles are generally parabolic but often highly asymmetric, with respect to the fracture walls. These asymmetric velocity profiles are clustered together, with significant correlations; they are not just local random phenomena. However, theoretical considerations indicate that the effects of the measured asymmetry on volumetric flow rates and hydraulic conductivities are insignificant, in that the overall flow inside rough fractures still obeys the cubic law. The features discussed in this study emphasize the strong heterogeneity and the highly three-dimensional nature of the flow patterns in natural rock fractures and consequently the need for three-dimensional flow analysis. IntroductionWater flow in rock fractures is of prime importance in subsurface hydrology and as a result has been studied extensively.

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“…The phase image itself can then be used to separate the dominant spectral information on a pixel-by-pixel basis. This concept has been used in a single point water/fat separation approach (7) and in imaging velocity using phase in MR angiography (MRA) (9). The problem with phase images has generally been the presence of background local fields that confound the effects of local phase changes in tissue.…”

mentioning

confidence: 99%

Susceptibility weighted imaging (SWI)

Haacke¹,

Xu²,

Cheng³

et al. 2004

Magnetic Resonance in Med

1,462

1,228

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Susceptibility differences between tissues can be utilized as a new type of contrast in MRI that is different from spin density, T 1 -, or T 2 -weighted imaging. Signals from substances with different magnetic susceptibilities compared to their neighboring tissue will become out of phase with these tissues at sufficiently long echo times (TEs). Thus, phase imaging offers a means of enhancing contrast in MRI. Specifically, the phase images themselves can provide excellent contrast between gray matter (GM) and white matter (WM), iron-laden tissues, venous blood vessels, and other tissues with susceptibilities that are different from the background tissue. Also, for the first time, projection phase images are shown to demonstrate tissue (vessel) continuity. In this work, the best approach for combining magnitude and phase images is discussed. The phase images are high-pass-filtered and then transformed to a special phase mask that varies in amplitude between zero and unity. This mask is multiplied a few times into the original magnitude image to create enhanced contrast between tissues with different susceptibilities.

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Measurement of Flow with NMR Imaging Using a Gradient Pulse and Phase Difference Technique

Cited by 512 publications

References 0 publications

Real-time magnetic resonance imaging of deep venous flow during muscular exercise—preliminary experience

Real-time magnetic resonance imaging of deep venous flow during muscular exercise—preliminary experience

Investigation of flow in water‐saturated rock fractures using nuclear magnetic resonance imaging (NMRI)

Susceptibility weighted imaging (SWI)

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