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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

2D Quantification (full).Results of ROI based quantitative analysis (averaged over all healthy subjects). On the left, minimum, maximum, and average values of vorticity are plotted over time. These plots deliver insight into the vortex strength and rotational direction. On the right, the percentage of clockwise and counter-clockwise flow relative to the entire lumen is depicted. These plots deliver information on the amount of opposing rotational flow components. Underlying data of the diagrams is provided in S2 Data.
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pone.0139025.g005: 2D Quantification (full).Results of ROI based quantitative analysis (averaged over all healthy subjects). On the left, minimum, maximum, and average values of vorticity are plotted over time. These plots deliver insight into the vortex strength and rotational direction. On the right, the percentage of clockwise and counter-clockwise flow relative to the entire lumen is depicted. These plots deliver information on the amount of opposing rotational flow components. Underlying data of the diagrams is provided in S2 Data.

Mentions: We aimed for an efficient integration of ROI based vortex analysis (Fig 3) yielding two-dimensional quantification of vortices (Figs 4 and 5). Therefore, a standardized set of 6 ROIs (Fig 4A) was defined for each dataset, 0: directly above the aortic bulb, 1: horizontal slice through the ascending aorta, 2: proximal to the brachiocephalic artery, 3: between the left common carotid artery and left subclavian artery, 4: distal to the left subclavian artery, 5: axial slice through the descending aorta at the level of ROI 1. All regions-of-interest were defined on cut planes perpendicular to the vessel lumen and restricted by the vessel wall. Positions were chosen according to standardized image interpretation guidelines [42,43] and slightly adjusted to fit into the specific context. For each ROI, a heatmap of time-resolved through-plane vorticity values was computed. The evolution of minimum, maximum, and average values throughout the cardiac cycle was plotted and analyzed (Figs 4 and 5). Since these values only contain information about vortex strength, the percentage of CW and CCW values exceeding an arbitrary threshold (set to 10 s-1 to suppress noise) was analyzed to estimate the amount of contrary rotational flow (Fig 5).


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)

2D Quantification (full).Results of ROI based quantitative analysis (averaged over all healthy subjects). On the left, minimum, maximum, and average values of vorticity are plotted over time. These plots deliver insight into the vortex strength and rotational direction. On the right, the percentage of clockwise and counter-clockwise flow relative to the entire lumen is depicted. These plots deliver information on the amount of opposing rotational flow components. Underlying data of the diagrams is provided in S2 Data.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0139025.g005: 2D Quantification (full).Results of ROI based quantitative analysis (averaged over all healthy subjects). On the left, minimum, maximum, and average values of vorticity are plotted over time. These plots deliver insight into the vortex strength and rotational direction. On the right, the percentage of clockwise and counter-clockwise flow relative to the entire lumen is depicted. These plots deliver information on the amount of opposing rotational flow components. Underlying data of the diagrams is provided in S2 Data.
Mentions: We aimed for an efficient integration of ROI based vortex analysis (Fig 3) yielding two-dimensional quantification of vortices (Figs 4 and 5). Therefore, a standardized set of 6 ROIs (Fig 4A) was defined for each dataset, 0: directly above the aortic bulb, 1: horizontal slice through the ascending aorta, 2: proximal to the brachiocephalic artery, 3: between the left common carotid artery and left subclavian artery, 4: distal to the left subclavian artery, 5: axial slice through the descending aorta at the level of ROI 1. All regions-of-interest were defined on cut planes perpendicular to the vessel lumen and restricted by the vessel wall. Positions were chosen according to standardized image interpretation guidelines [42,43] and slightly adjusted to fit into the specific context. For each ROI, a heatmap of time-resolved through-plane vorticity values was computed. The evolution of minimum, maximum, and average values throughout the cardiac cycle was plotted and analyzed (Figs 4 and 5). Since these values only contain information about vortex strength, the percentage of CW and CCW values exceeding an arbitrary threshold (set to 10 s-1 to suppress noise) was analyzed to estimate the amount of contrary rotational flow (Fig 5).

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