B-Spline Surface Mapping To Describe Aorta Kinematics During Cardiac Cycle

Abstract eng:
The dynamic behaviour of the aorta is an important issue for the clinical reality, since this vascular district is now the target of minimally invasive approaches like EVAR (endovascular aortic repair), which are applying endograft prosthesis to exclude aneurysm or ruptures. The assessment of the aorta dynamics is now performed analyzing the images obtained by the so-called 4D Computed Tomography Angiography; in this procedure, a CTA scans is performed in several (usually 8) time frame obtaining thus a sort of snapshot collection of the aorta configuration during the cardiac cycle. Since the CTA is ECG-gated, it is possible to relate the lumen vascular profile with a given blood pressure. The analysis of the images is aimed to assess the diameter change of the aorta along the cardiac cycle at given (anatomically-relevant) locations and it is usually performed by semi-automatic procedures: for each time frame the centerline of the vessel is generated and the diameter of the crosssection is then calculated [1]. Despite some medical study is already addressing this topic, we think that there is still room for improvement and automatization of the procedure; in fact the basic idea is to generate a framework defined by the following steps: • generation of n STL surfaces of the aorta, where n is the number of cardiac frame; the segmentation will focus only on the main vessel neglecting the branches; • generation of a B-spline surface (RS) corresponding to the vessel lumen at the first frame; in this way, we will define the base functions describing the 3D object, i.e., the aorta; • fitting RS to the other frames. The framework should provide a conformal continue representation of vessel along the time (under certain hypothesis, a fitting in time can be also performed). The result can be used to enhance the visualization of aorta configuration during the cardiac cycle and calculating compute radius, displacements etc. in a fast way. Moreover, the B-spline surface can be exploited for biomechanical isogeometric analysis or for the setting of coupled problems as discussed by [2].

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