Combined analysis of spatial and velocity displacement artifacts in phase contrast measurements of complex flows

Steinman, David A.; Ethier, C. Ross; Rutt, Brian K.

doi:10.1002/jmri.1880070214

Cited by 57 publications

(71 citation statements)

References 24 publications

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“…The measurement near the walls was somewhat compromised due to the velocity gradients across those pixels in the presence of B o distortion arising from the stent material. These gradients can lead to intravoxel-phase dispersion as described in previous investigations (8,9).…”

Section: Discussionmentioning

confidence: 54%

Magnetic resonance phase velocity mapping through NiTi stents in a flow phantom model

Walsh

Holton

Brott

et al. 2004

Magnetic Resonance Imaging

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Purpose: To assess constant and pulsatile flow velocity within the lumen of a peripheral NiTi stent using phase velocity mapping for comparison with independent assessments of flow velocity in a phantom model. Materials and Methods:A 9 ϫ 20-mm stent installed in flexible tubing was placed in a phantom filled with stationary fluid. Constant and pulsatile flow (produced by a pump programmed to produce a simulation of the carotid artery flow) was assessed using phase velocity mapping at 4.1 T (for constant flow) and at 1.5 T (for pulsatile flow). In all cases 256 ϫ 256 gradient echo phase velocity maps were acquired. For the pulsatile flow condition, cine images with acquisition gated to the pump cycle were acquired with 40 msec temporal resolution across the simulated cardiac cycle. Computed flow volume rates were compared with fluid volume collection for the constant flow model, and with ultrasonic Doppler flow meter measurements for the pulsatile model. Results:The data showed that volume flow rate assessments by phase velocity mapping agreed with independent measurements within 10% to 15%. MR AND CT ANGIOGRAPHY are routinely used in the assessment of vascular patency and in-stent pathology. However, both provide only morphologic information and require exposure to ionizing radiation. MRI traditionally has been limited in its ability to assess vascular stent patency due to susceptibility artifacts and radiofrequency shielding. It has been shown that stents made from nickel-titanium (NiTi) alloys produce susceptibility artifacts of smaller extent than those produced by similar devices made from stainless steel. Self-expanding NiTi device placement procedures are also less likely to result in vessel wall damage, since a high-pressure balloon deployment system is not required in order to conform the stent to the vessel wall. NiTi self-expanding devices presently account for 100% of carotid and femoral artery stenting procedures and 70% of saphenous vein bypass graft stenting procedures (1). ConclusionWith the inherent signal-to-noise ratio (SNR) and spatial resolution of MRI, characterization of arterial anatomy with MRI is superior to that obtained with carotid duplex ultrasound scanning (2). Advances in fast MRI techniques enable comprehensive study of both cardiac morphology, function, blood flow, perfusion (3), and also coronary artery bypass graft function (4,5).The present study examined the quantitative assessment of flow through the lumen of a NiTi stent. The device was of a size typical for use in peripheral arteries and bypass grafts to provide for a larger number of pixels for flow computation than would be possible in a coronary-sized device given typical pixel resolutions in patient studies.Since utilization of MRI through stented regions has been limited, this study attempted flow measurements through a NiTi stent in both continuous and more clinically relevant pulsatile flows. The aim of this study was to demonstrate the feasibility of using MRI through metallic stents in quantitative determinations ...

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Section: Discussionmentioning

confidence: 54%

Magnetic resonance phase velocity mapping through NiTi stents in a flow phantom model

Walsh

Holton

Brott

et al. 2004

Magnetic Resonance Imaging

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“…Thus, the imaging plane cannot be ensured to be perpendicular to the flow throughout the cross-section of the aneurysm. The above mentioned partial volume effects, together with displacement artifacts due to the non-simultaneity of spatial encoding in PC-MRA, as described by Steinman et al (32) can be expected to limit the accuracy of velocity measurements in the intraaneurysmal flow. Consequently, even with the minimum possible slice thickness of 0.7 mm used here, it is rather difficult and time consuming to develop a full 3D velocity profile suitable for making a precise statement on the velocity patterns in small to middle sized aneurysms like in this model with dimensions of about 7 ϫ 5 ϫ 5 mm.…”

Section: Discussionmentioning

confidence: 99%

Laser Doppler velocimetry (LDV) and 3D phase‐contrast magnetic resonance angiography (PC‐MRA) velocity measurements: Validation in an anatomically accurate cerebral artery aneurysm model with steady flow

Hollnagel

Summers

Kollias

et al. 2007

Magnetic Resonance Imaging

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Purpose:To verify the accuracy of velocity mapping with three-dimensional (3D) phase-contrast magnetic resonance angiography (PC-MRA) for steady flow in a realistic model of a cerebral artery aneurysm at a 3T scanner. Materials and Methods:Steady flow through an original geometry model of a cerebral aneurysm was mapped at characteristic positions by state-of-the-art laser Doppler velocimetry (LDV) as well as 3D PC-MRA at 3T. The spatial distributions and local values of two velocity components obtained with these two measurement methods were compared. Results:The 3D PC-MRA velocity field distribution and mean velocity values exhibited only minor differences to compare to the LDV measurements in straight artery regions for both main and secondary velocities. The differences increased in regions with disturbed flow and in cases where the measurement plane was not perpendicular to the main flow direction.Conclusion: 3D PC-MRA can provide reliable measurements of velocity components of steady flow in small arteries. The accuracy of such measurements depends on the artery size and the measurement plane positioning.

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“…Depiction of flow jets with short spiral readouts has also been successfully performed [15]. A further advantage of non-Cartesian sequences is that in-plane spatial encoding occurs at a single point in time, while timing for readout and phase encoding differ in Cartesian sequences, which can introduce errors and artifacts [16]. A drawback of using spiral trajectories is that the temporal proximity of encoding gradients to the readout of the centre of k-space is expected to increase background phase offsets.…”

Section: An Alternative Non-invasive Methods For Blood Velocity Measurmentioning

confidence: 99%

“…The distortion in the jet shape found in Cartesian sequences as seen in Fig. 8 can be related to the timing of position and velocity encoding in the sequence [16]. In the Cartesian sequences the positional encoding in the directions perpendicular to the jet occurs at different time points, whereas in the spiral sequence no such time difference exists.…”

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confidence: 97%

Volumetric velocity measurements in restricted geometries using spiral sampling: a phantom study

Nilsson

Revstedt

Heiberg

et al. 2014

Magn Reson Mater Phy

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Object:To evaluate the accuracy of maximum velocity measurements using volumetric phase contrast imaging with spiral readouts in a stenotic flow phantom. Materials and Methods:In a phantom model, maximum velocity, flow, pressure gradient and streamline visualizations were evaluated using volumetric phase contrast MRI with velocity encoding in one (extending on current clinical practice) and three directions (for characterization of the flow field) using spiral readouts.Results of maximum velocity and pressure drop were compared to CFD simulations (Computational Fluid Dynamics), as well as corresponding low-TE Cartesian data. Flow was compared to 2D throughplane PC upstream from the restriction. Results:Results obtained with 3D throughplane PC as well as 4D PC at shortest TE using spiral readout showed excellent agreements with the maximum velocity values obtained with CFD (<1% for both methods), while larger deviations were seen using Cartesian readouts (-2% and 13%, respectively).Peak pressure drop calculated from 3D throughplane PC and 4D PC spiral sequences was 14% and 13% overestimated compared to CFD. Conclusion:Identification of the maximum velocity location as well as accurate velocity quantification can be obtained in stenotic regions using short-TE spiral volumetric PC imaging.3

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Combined analysis of spatial and velocity displacement artifacts in phase contrast measurements of complex flows

Cited by 57 publications

References 24 publications

Magnetic resonance phase velocity mapping through NiTi stents in a flow phantom model

Magnetic resonance phase velocity mapping through NiTi stents in a flow phantom model

Laser Doppler velocimetry (LDV) and 3D phase‐contrast magnetic resonance angiography (PC‐MRA) velocity measurements: Validation in an anatomically accurate cerebral artery aneurysm model with steady flow

Volumetric velocity measurements in restricted geometries using spiral sampling: a phantom study

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