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Updated: Mar 16, 2026
In vitro Assessment of Aortic Regurgitation Using Four-Dimensional Flow Magnetic Resonance Imaging
Published on: February 25, 2022
Volumetric quantification of absolute local normalized helicity in patients with bicuspid aortic valve and aortic
Julio Garcia1,2, Alex J Barker1, Jeremy D Collins1
1Department of Radiology, Northwestern University, Chicago, IL, USA.
Insights
Absolute local normalized helicity (LNH) effectively distinguishes flow differences in bicuspid aortic valve (BAV) patients from healthy individuals. This metric correlates with aortic diameter and stenosis severity, aiding in diagnosis.
Area of Science:
- Cardiovascular Imaging
- Biomedical Engineering
- Flow Physics
Background:
- Bicuspid aortic valve (BAV) is a common congenital heart defect.
- Altered blood flow patterns in the aorta are associated with BAV and can lead to complications.
- Non-invasive imaging techniques are crucial for assessing aortic hemodynamics.
Purpose of the Study:
- To evaluate the efficacy of absolute local normalized helicity (LNH) in differentiating aortic flow alterations between healthy controls and BAV patients.
- To determine the correlation of absolute LNH with aortic diameter and stenosis severity.
Main Methods:
- Four-dimensional (4D) flow MRI was performed on 65 controls and 50 BAV patients.
- Three-dimensional (3D) segmentation of the thoracic aorta was conducted.
- Absolute LNH was calculated and analyzed across different cardiac phases (peak systole, systolic deceleration, middiastole).
- Sensitivity and reproducibility analyses were performed.
Main Results:
- Absolute LNH was significantly higher in BAV patients compared to controls across all aortic segments and cardiac time frames (P < 0.001).
- A threshold of absolute LNH > 0.6 differentiated BAV from controls.
- Absolute LNH in the ascending aorta showed strong correlations with maximal aortic diameter (R = 0.83-0.88) and increased with aortic stenosis severity (P < 0.001).
- Intra- and interobserver variability for 3D segmentation and LNH calculation were acceptable.
Conclusions:
- Absolute LNH is a valuable quantitative marker for differentiating aortic flow alterations in BAV patients.
- Absolute LNH is associated with aortic dilatation and stenosis severity, offering potential for improved diagnostic assessment.
- 4D flow MRI combined with LNH analysis provides a powerful tool for evaluating BAV-related hemodynamics.
Purpose:
Absolute local normalized helicity (LNH) can differentiate flow alterations in the aorta between healthy controls and bicuspid aortic valve (BAV) patients.
Methods:
A total of 65 controls and 50 subjects with BAV underwent in vivo four-dimensional (4D) flow MRI. Data analysis included the three-dimensional (3D) segmentation of the thoracic aorta (ascending aorta, aortic arch, and descending aorta) and calculation of absolute LNH. The mean velocity in the entire aorta was used to identify peak systole, systolic deceleration, and middiastole. A sensitivity analysis was performed to identify the optimal absolute LNH threshold, comparing control and BAV groups. A reproducibility test was performed for 3D segmentation and absolute LNH.
Results:
Absolute LNH above 0.6 was significantly higher (P < 0.001) in BAV in comparison to controls for all aortic segments and cardiac time frames. Absolute LNH in the ascending aorta correlated with maximal aortic diameter (R = 0.83, P < 0.001, at peak systole; r = 0.84, P < 0.001, at systolic deceleration; R = 0.88, P < 0.001, at middiastole) and significantly increased (P < 0.001) with aortic stenosis severity. Intra- and interobserver errors were 5 ± 2% and 12 ± 6% for 3D segmentation and 7 ± 6% and 12 ± 7% for absolute LNH.
Conclusion:
Absolute LNH can differentiate between controls and subjects with aortic dilatation, and was associated with maximal aortic diameter and aortic stenosis severity. Magn Reson Med 78:689-701, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
