Improved quantification of abnormal aortic flow in 3D compared to standard 2D approach
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KeywordsAortic Stenosis Bicuspid Aortic Valve Aortic Valve Disease Aortic Pathology Vessel Centerline
With 4D MR flow imaging, eccentric flow has been reported in patients with bicuspid aortic valve (BAV) and investigated as a risk factor for ascending aortic (AsAo) aneurysms . We have demonstrated that a new parameter, normalized displacement, quantifies the degree of flow eccentricity in the AsAo . However, it only offers information on a single location in the AsAo. The aim of the current work was to extend the normalized displacement parameter to utilize the entire 4D flow information. We developed a 3D analysis method and analyzed the degree and pattern of eccentric systolic flow in the AsAo of individuals with different aortic pathologies.
A 3D Phase-Contrast MRI pulse sequence was used to assess blood flow in the thoracic aorta. MR imaging was performed at 1.5T (Siemens Avanto, and Signa, GE). Informed consent was obtained from all participants.
28 subjects were divided in 5 groups based on their aortic pathology: Normal (n=6), BAV without aortic stenosis (AS) or dilatation (n=7), TAV with AS, no dilatation (n=3), TAV with dilatation, no AS (n=6), and TAV with both AS and dilatation (n=6).
Representative plots of normalized displacement from multiple cross-sections as a function of distance along the AsAo are presented in Figure 1 for a BAV subject (B), and two TAV + AS & Dilation subjects (C, D). Flow patterns had similar characteristics within a group of subjects. Generally, presence of AS was related to a rapid increase in normalized displacement, followed by a plateau. Normalized displacement variation along the AsAo for BAV subjects presented an increase followed by an immediate decrease of values, with absence of a plateau.
The improved 3D flow displacement analysis allows visualization of the flow pattern along the ascending aorta, and enables detection of characteristics specific to different aortic pathologies. Furthermore, the 3D method better captures abnormal flow with aortic valve disease than the standard 2D analysis.
Covidien/Radiologic Society of North America Research Scholar Grant 2012-2014.
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