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Quantitative Analysis of Vortical Blood Flow in the Thoracic Aorta Using 4D Phase Contrast MRI.

von Spiczak J, Crelier G, Giese D, Kozerke S, Maintz D, Bunck AC - PLoS ONE (2015)

Bottom Line: Strength, elongation, and radial expansion of 3D vortex cores escalated in early systole, reaching a peak in mid systole (strength = 241.2±30.7 s-1 at 17%, elongation = 65.1±34.6 mm at 18%, expansion = 80.1±48.8 mm2 at 20%), before all three parameters similarly decreased to overall low values in diastole.Flow patterns were considerably altered in patient data: Vortex flow developed late in mid/end-systole close to the aortic bulb and no physiological helix was found in the aortic arch.In patient data, pathologically altered vortex flow was observed.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and Neuroradiology, University Hospital of Cologne, Cologne, Germany.

ABSTRACT

Introduction: Phase contrast MRI allows for the examination of complex hemodynamics in the heart and adjacent great vessels. Vortex flow patterns seem to play an important role in certain vascular pathologies. We propose two- and three-dimensional metrics for the objective quantification of aortic vortex blood flow in 4D phase contrast MRI.

Materials and methods: For two-dimensional vorticity assessment, a standardized set of 6 regions-of-interest (ROIs) was defined throughout the course of the aorta. For each ROI, a heatmap of time-resolved vorticity values [Formula: see text] was computed. Evolution of minimum, maximum, and average values as well as opposing rotational flow components were analyzed. For three-dimensional analysis, vortex core detection was implemented combining the predictor-corrector method with λ2 correction. Strength, elongation, and radial expansion of the detected vortex core were recorded over time. All methods were applied to 4D flow MRI datasets of 9 healthy subjects, 2 patients with mildly dilated aorta, and 1 patient with aortic aneurysm.

Results: Vorticity quantification in the 6 standardized ROIs enabled the description of physiological vortex flow in the healthy aorta. Helical flow developed early in the ascending aorta (absolute vorticity = 166.4±86.4 s-1 at 12% of cardiac cycle) followed by maximum values in mid-systole in the aortic arch (240.1±45.2 s-1 at 16%). Strength, elongation, and radial expansion of 3D vortex cores escalated in early systole, reaching a peak in mid systole (strength = 241.2±30.7 s-1 at 17%, elongation = 65.1±34.6 mm at 18%, expansion = 80.1±48.8 mm2 at 20%), before all three parameters similarly decreased to overall low values in diastole. Flow patterns were considerably altered in patient data: Vortex flow developed late in mid/end-systole close to the aortic bulb and no physiological helix was found in the aortic arch.

Conclusions: We have introduced objective measures for quantification of vortical flow in 4D phase contrast MRI. Vortex blood flow in the thoracic aorta could be consistently described in all healthy volunteers. In patient data, pathologically altered vortex flow was observed.

No MeSH data available.


Related in: MedlinePlus

Vorticity Calculation.(A) Vorticity is defined as the curl of the velocity field (equal to (∂vy/∂x– ∂vx/∂y)ez in the two-dimensional case), describing the tendency of a single fluid element to spin around its axis (as shown for a counter-clockwise rotating vortex; figure similar to [5]). (B) Illustration of the velocity field defined by the Lamb-Oseen equation, giving a theoretical approximation of a planar vortex. The solid line denotes the tangential velocity profile, while the dotted line depicts its first derivative. Note the derivative’s maximum in the vortex center due to the sudden shift of velocity values. (C) Artificial sample data superimposing a planar vortex on the parabolic velocity profile through a simple tube. Note the vortical movement of pathlines in the middle of the tube, intersecting ROIs exhibiting vorticity values, and the correctly identified vortex core.
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pone.0139025.g001: Vorticity Calculation.(A) Vorticity is defined as the curl of the velocity field (equal to (∂vy/∂x– ∂vx/∂y)ez in the two-dimensional case), describing the tendency of a single fluid element to spin around its axis (as shown for a counter-clockwise rotating vortex; figure similar to [5]). (B) Illustration of the velocity field defined by the Lamb-Oseen equation, giving a theoretical approximation of a planar vortex. The solid line denotes the tangential velocity profile, while the dotted line depicts its first derivative. Note the derivative’s maximum in the vortex center due to the sudden shift of velocity values. (C) Artificial sample data superimposing a planar vortex on the parabolic velocity profile through a simple tube. Note the vortical movement of pathlines in the middle of the tube, intersecting ROIs exhibiting vorticity values, and the correctly identified vortex core.

Mentions: To provide a basis for further methods outlined below, calculation of vorticity of the time-resolved three-dimensional vector field derived from 4D flow MRI measurements was implemented. The vorticity ω is defined as the curl of the velocity vector field [37] (Fig 1A):ω→=∇v→with∇v→=(∂∂x,∂∂y,∂∂z)(vx,vy,vz)=(∂vz∂y−∂vy∂z,∂vx∂z−∂vz∂x,∂vy∂x−∂vx∂y).


Quantitative Analysis of Vortical Blood Flow in the Thoracic Aorta Using 4D Phase Contrast MRI.

von Spiczak J, Crelier G, Giese D, Kozerke S, Maintz D, Bunck AC - PLoS ONE (2015)

Vorticity Calculation.(A) Vorticity is defined as the curl of the velocity field (equal to (∂vy/∂x– ∂vx/∂y)ez in the two-dimensional case), describing the tendency of a single fluid element to spin around its axis (as shown for a counter-clockwise rotating vortex; figure similar to [5]). (B) Illustration of the velocity field defined by the Lamb-Oseen equation, giving a theoretical approximation of a planar vortex. The solid line denotes the tangential velocity profile, while the dotted line depicts its first derivative. Note the derivative’s maximum in the vortex center due to the sudden shift of velocity values. (C) Artificial sample data superimposing a planar vortex on the parabolic velocity profile through a simple tube. Note the vortical movement of pathlines in the middle of the tube, intersecting ROIs exhibiting vorticity values, and the correctly identified vortex core.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4587936&req=5

pone.0139025.g001: Vorticity Calculation.(A) Vorticity is defined as the curl of the velocity field (equal to (∂vy/∂x– ∂vx/∂y)ez in the two-dimensional case), describing the tendency of a single fluid element to spin around its axis (as shown for a counter-clockwise rotating vortex; figure similar to [5]). (B) Illustration of the velocity field defined by the Lamb-Oseen equation, giving a theoretical approximation of a planar vortex. The solid line denotes the tangential velocity profile, while the dotted line depicts its first derivative. Note the derivative’s maximum in the vortex center due to the sudden shift of velocity values. (C) Artificial sample data superimposing a planar vortex on the parabolic velocity profile through a simple tube. Note the vortical movement of pathlines in the middle of the tube, intersecting ROIs exhibiting vorticity values, and the correctly identified vortex core.
Mentions: To provide a basis for further methods outlined below, calculation of vorticity of the time-resolved three-dimensional vector field derived from 4D flow MRI measurements was implemented. The vorticity ω is defined as the curl of the velocity vector field [37] (Fig 1A):ω→=∇v→with∇v→=(∂∂x,∂∂y,∂∂z)(vx,vy,vz)=(∂vz∂y−∂vy∂z,∂vx∂z−∂vz∂x,∂vy∂x−∂vx∂y).

Bottom Line: Strength, elongation, and radial expansion of 3D vortex cores escalated in early systole, reaching a peak in mid systole (strength = 241.2±30.7 s-1 at 17%, elongation = 65.1±34.6 mm at 18%, expansion = 80.1±48.8 mm2 at 20%), before all three parameters similarly decreased to overall low values in diastole.Flow patterns were considerably altered in patient data: Vortex flow developed late in mid/end-systole close to the aortic bulb and no physiological helix was found in the aortic arch.In patient data, pathologically altered vortex flow was observed.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and Neuroradiology, University Hospital of Cologne, Cologne, Germany.

ABSTRACT

Introduction: Phase contrast MRI allows for the examination of complex hemodynamics in the heart and adjacent great vessels. Vortex flow patterns seem to play an important role in certain vascular pathologies. We propose two- and three-dimensional metrics for the objective quantification of aortic vortex blood flow in 4D phase contrast MRI.

Materials and methods: For two-dimensional vorticity assessment, a standardized set of 6 regions-of-interest (ROIs) was defined throughout the course of the aorta. For each ROI, a heatmap of time-resolved vorticity values [Formula: see text] was computed. Evolution of minimum, maximum, and average values as well as opposing rotational flow components were analyzed. For three-dimensional analysis, vortex core detection was implemented combining the predictor-corrector method with λ2 correction. Strength, elongation, and radial expansion of the detected vortex core were recorded over time. All methods were applied to 4D flow MRI datasets of 9 healthy subjects, 2 patients with mildly dilated aorta, and 1 patient with aortic aneurysm.

Results: Vorticity quantification in the 6 standardized ROIs enabled the description of physiological vortex flow in the healthy aorta. Helical flow developed early in the ascending aorta (absolute vorticity = 166.4±86.4 s-1 at 12% of cardiac cycle) followed by maximum values in mid-systole in the aortic arch (240.1±45.2 s-1 at 16%). Strength, elongation, and radial expansion of 3D vortex cores escalated in early systole, reaching a peak in mid systole (strength = 241.2±30.7 s-1 at 17%, elongation = 65.1±34.6 mm at 18%, expansion = 80.1±48.8 mm2 at 20%), before all three parameters similarly decreased to overall low values in diastole. Flow patterns were considerably altered in patient data: Vortex flow developed late in mid/end-systole close to the aortic bulb and no physiological helix was found in the aortic arch.

Conclusions: We have introduced objective measures for quantification of vortical flow in 4D phase contrast MRI. Vortex blood flow in the thoracic aorta could be consistently described in all healthy volunteers. In patient data, pathologically altered vortex flow was observed.

No MeSH data available.


Related in: MedlinePlus