Abstract
PurposeEvaluate spiral three‐dimensional (3D) phase contrast MRI for the assessment of turbulence and velocity in stenotic flow.MethodsA‐stack‐of‐spirals 3D phase contrast MRI sequence was evaluated in vitro against a conventional Cartesian sequence. Measurements were made in a flow phantom with a 75% stenosis. Both spiral and Cartesian imaging were performed using different scan orientations and flow rates. Volume flow rate, maximum velocity and turbulent kinetic energy (TKE) were computed for both methods. Moreover, the estimated TKE was compared with computational fluid dynamics (CFD) data.ResultsThere was good agreement between the turbulent kinetic energy from the spiral, Cartesian and CFD data. Flow rate and maximum velocity from the spiral data agreed well with Cartesian data. As expected, the short echo time of the spiral sequence resulted in less prominent displacement artifacts compared with the Cartesian sequence. However, both spiral and Cartesian flow rate estimates were sensitive to displacement when the flow was oblique to the encoding directions.ConclusionSpiral 3D phase contrast MRI appears favorable for the assessment of stenotic flow. The spiral sequence was more than three times faster and less sensitive to displacement artifacts when compared with a conventional Cartesian sequence. Magn Reson Med 75:1249–1255, 2016. © 2015 Wiley Periodicals, Inc.
Highlights
Stenotic flow is often characterized by high-velocity jets, high acceleration, and disturbed or turbulent flow fluctuations
The application of 4D flow MRI is limited by long scan times and many PC-MRI artifacts are more prominent in stenotic flow
The estimated maximum velocities were in the interval of 1.37 to 1.46 m/s and 1.34 to 1.39 m/s for the spiral and Cartesian measurements of the increased-flow case, respectively (Table 2)
Summary
Stenotic flow is often characterized by high-velocity jets, high acceleration, and disturbed or turbulent flow fluctuations. These turbulent flow fluctuations drastically decrease the transport efficiency of the blood due to viscous dissipation, which is the major cause of pressure drop over a constriction. Disturbed and turbulent flow can cause flow-related signal loss due to intravoxel phase dispersion [8], and ghosting due to view-to-view variations. This signal loss can lead to inaccurate flow estimates, but can be decreased by usage of shorter echo times (TE) [8]. Ultrashort TE PC-MRI have been shown to reduce artifacts such as signal loss, as well as to increase the accuracy of flow quantification of stenotic flow [9,10,11], but it does not decrease the long scan times
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