Self-calibrated epipolar reconstruction for assessment of aneurysms in the internal carotid artery using in-silico biplane angiograms

Background: The treatment of intracranial aneurysms (IA) predominantly relies on angiography guidance using biplane views. However, accurate flow estimation and device sizing for treatment are often compromised by vessel overlap and foreshortening, which can obscure critical details. Purpose: This study introduces an epipolar reconstruction approach to enhance three-dimensional (3D) rendering of the internal carotid artery (ICA) and aneurysm dome using standard, routinely acquired biplane angiographic data. Our method aims to improve procedural guidance and device selection by overcoming the limitations of traditional two-dimensional imaging techniques. Methods: This study employed three 3D geometries of ICA aneurysms to simulate virtual angiograms, including the aneurysm dome, parent vessel, tortuous carotid cavernous segment and the ICA terminus bifurcation. Virtual angiograms were generated using a computational fluid dynamics (CFD) solver, followed by the simulation of biplane angiography using a cone-beam geometry. Self-calibration was accomplished by matching contrast media position as a function of time between biplane views. Feature-matching based on axial positioning was used to triangulate and reconstruct the vascular structures in 3D. The projection data was utilized to refine the 3D estimation, including elimination of erroneous structures and ellipse-fitting. The accuracy of the reconstructed images was quantitatively evaluated using the Dice-Sorensen coefficient, comparing the 3D reconstructions to the original CFD-generated models to assess the geometric fidelity. Results: The proposed epipolar reconstruction method generalized well across the three tested aneurysm models, with respective Dice-Sorensen coefficients of 0.745, 0.759, and 0.654. Errors were primarily due to partial vessel overlap, observed in our third model. The average reconstruction time for all three volumes was approximately 10 s. Conclusions: The implemented epipolar reconstruction method enhanced 3D visualizations from biplane angiographic data, addressing key challenges such as projection-induced vessel foreshortening. This method provides a solution to the complexity of IA visualization, with the potential to provide more accurate analysis and device sizing for treatment.