In patients undergoing vascular surgeries (e.g., bypass grafting), the use of intraoperative blood flow measurements has proven to be effective in reducing recurrence rate. This is made possible by Optical Coherence Tomography Angiography (OCTA).
OCTA is a contact-free technique to visualize vascular flow based on the motion and scattering of erythrocytes. Therefore, repeated Optical Coherence Tomography (OCT) scans are performed to detect motion contrast and to visualize vasculature. Although OCTA is already used in clinical settings, it is primarily a qualitative tool. Up to now, there is no quantitative blood flow assessment available based on OCT hardware and OCTA algorithms.
In this project, the application areas of OCTA will be expanded and its limitations will be explored. The goal is to quantitatively correlate the OCTA signal with blood flow in large vessels by measuring this signal at a single location of the vessel.
Approximating the fast dynamics of depolarization waves in the human heart described by the monodomain model is numerically challenging. Splitting methods for the PDE-ODE coupling enable the computation with very fine space and time discretizations. Here, we compare different splitting approaches regarding convergence, accuracy, and efficiency. Simulations were performed for a benchmark problem with the Beeler-Reuter cell model on a truncated ellipsoid approximating the left ventricle including a localized stimulation. For this configuration, we provide a reference solution for the transmembrane potential. We found a semi-implicit approach with state variable interpolation to be the most efficient scheme. The results are transferred to a more physiological setup using a bi-ventricular domain with a complex external stimulation pattern to evaluate the accuracy of the activation time for different resolutions in space and time.