Korean J Radiol.  2016 Aug;17(4):445-462. 10.3348/kjr.2016.17.4.445.

Hemodynamic Measurement Using Four-Dimensional Phase-Contrast MRI: Quantification of Hemodynamic Parameters and Clinical Applications

• Ha H
• Kim GB
• Kweon J
• Lee SJ
• Kim YH
• Lee DH
• Yang DH
• Kim N

• KMID: 2455416
• DOI: http://doi.org/10.3348/kjr.2016.17.4.445

Abstract

Recent improvements have been made to the use of time-resolved, three-dimensional phase-contrast (PC) magnetic resonance imaging (MRI), which is also named four-dimensional (4D) PC-MRI or 4D flow MRI, in the investigation of spatial and temporal variations in hemodynamic features in cardiovascular blood flow. The present article reviews the principle and analytical procedures of 4D PC-MRI. Various fluid dynamic biomarkers for possible clinical usage are also described, including wall shear stress, turbulent kinetic energy, and relative pressure. Lastly, this article provides an overview of the clinical applications of 4D PC-MRI in various cardiovascular regions.

Keyword

4D phase-contrast MRI; 4D flow MRI; Blood flow; Hemodynamics

MeSH Terms

Algorithms
Blood Flow Velocity
Coronary Vessels/*diagnostic imaging
Heart/*diagnostic imaging
Hemodynamics/*physiology
Humans
Imaging, Three-Dimensional
*Magnetic Resonance Imaging
Shear Strength
Thermodynamics

Figure

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  Fig. 1 Principles of 2D PC-MRI and 4D PC-MRI. Conventional PC-MRI uses bipolar gradient along flow-encoding direction before readout sequence. Bipolar gradient removes phase accumulations from stationary spins, which results in only background phase offset and flow-related phase accumulations. PC-MRI sequence typically uses two acquisitions with different M1 values to remove unknown phase offset. PC = phase-contrast, 2D = two-dimensional, 4D = four-dimensional

• 

  Fig. 2 Procedures for 4D PC-MRI. Image quality of raw data can be influenced by adequate scan parameters including field of view, spatial resolution, temporal resolution, and VENC. In addition, appropriate pre-processing and data analysis techniques are also important for accurate quantification of hemodynamic features. PC = phase-contrast, ROI = region of interest, 4D = four-dimensional

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  Fig. 3 Velocity visualization and quantification of flow rate. Streamline and velocity vector (left panel) can be used to visualize blood flow pattern in aorta. Spatial and temporal variation of blood flow can also be quantified by integrating four-dimensional velocity field data (right panel).

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  Fig. 4 Wall shear stress (WSS) estimation using 4D PC-MRI. First step for WSS estimation is to obtain smooth spline contour or surface of lumen from magnitude, phase, or mask images, so that wall location and normal displacement vector can be estimated from lumen contour or surface. WSS can be obtained by multiplying velocity gradient and blood viscosity. PC = phase-contrast, 4D = four-dimensional

• 

  Fig. 5 Principle of TKE estimation. TKE estimation is based on relationship between intravoxel velocity distribution and MR signal from standard PC-MRI scan. Therefore, TKE can be quantified from quantification of magnitude difference under velocity gradient. IVSD = intra-voxel standard deviation, PC = phase-contrast, TKE = turbulent kinetic energy

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  Fig. 6 Identification of vortical flow pattern. A. Vorticity in rotational flow. B. λci quantification in aortic flow. Note that vortical flow structures induce high vorticity and λci.

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  Fig. 7 Procedures for estimation of relative pressure field. Since 4D PC-MRI provides 4D spatio-temporal velocity field, it can be employed to quantify 4D relative pressure distribution along vessel by solving Navier-Stokes equation and reconstructing pressure field over entire vessel of interest. Right panels show representative velocity field and pressure drop through stenotic vessel. PC = phase-contrast, 4D = four-dimensional

• 

  Fig. 8 Examples of 4D flow cardiac magnetic resonance visualization techniques, demonstrated on intracardiac flow data acquired in healthy volunteer In these examples, flow visualization is overlaid onto 2D bSSFP acquisition in three-chamber view. A. Pathlines are trajectories that massless fluid particles would follow through dynamic velocity field and are suitable for studies of path of pulsatile blood flow over time. Here, transit of blood through left ventricle (LV) is shown by pathlines emitted from mitral valve at time point of peak A-wave and traced to time point of early systole. Timing of ECG is included for reference. B-D. Streamlines are instantaneously tangential to velocity vector field and are useful for visualizing 3D velocity fields at discrete time points. Here, streamlines generated in long-axis plane show parts of intracardiac velocity field at time points of peak early filling (E-wave) (B), peak late filling (A-wave) (C), and peak systole (D). Adapted from Dyverfeldt et al. J Cardiovasc Magn Reson 2015;17:72 (30).

• 

  Fig. 9 Visualization of aortic flow. Normal subject (A), patient with aortic stenosis (B), and patient with aortic regurgitation and aortic root dilatation at systole flow (C) and diastole flow (D). Note that aortic flow with aortic stenosis causes helical flow patterns. Aortic flow with aortic dilatation causes impinging flow pattern at systole flow, and substantial amount of regurgitation flow is observed.

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  Fig. 10 Comparison of patients with normal (A) and abnormal (B) prosthetic valves. Inset panels indicate opening of prosthetic valves. Note that only abnormal prosthetic valves with partial opening failure generate complex helical blood flow.

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  Fig. 11 4D PC-MRI measurement of patient with pulmonary hypertension. A, B. Pathline visualization at early systole (A) and early diastole (B). C. Planar vector visualization of vortical flow pattern. Red arrows indicate center of vortical flow pattern. Note that vortical flow structure at main pulmonary artery appears from early diastole phase. PC = phase-contrast, 4D = four-dimensional

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  Fig. 12 4D PC-MRI measurement of intracranial blood flow. Single volume acquisition using 4D PC-MRI provides volumetric flow distribution in circle of Willis. PC = phase-contrast, 4D = four-dimensional

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  Fig. 13 Turbulent kinetic energy (TKE) estimation using 4D PC-MRI. Normal subject (A), patient with aortic stenosis with bicuspid aortic valve (B), and patient with aortic stenosis with tricuspid aortic valve (C). Note that patients with aortic stenosis have higher TKE distributions than normal subjects.

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