Investigating Leptomeningeal Anastomoses' Role in Collateral Blood Flow using SPECT and 4D Flow MRI.

Leptomeningeal anastomoses (LMAs) are vital components of cerebral collateral circulation, but their small size and inter-patient variability hinder direct quantitative assessment in patient-specific cases. This study investigates the functional role of LMAs and their vessel-level interactions with the cerebral vasculature, using patient-specific flow data and accounting for uncertainty in peripheral vessel anatomy. Synthetic vascular trees were generated via a stochastic, anatomically informed sampling process. Assuming that discrepancies between 4D Flow MRI and Single-Photon Emission Computed Tomography (SPECT) are attributable to LMA-mediated redistribution, LMA configurations were optimized using an island genetic algorithm (IGA) to minimize residuals between simulated distal flows and SPECT-derived perfusion data. The resulting configurations successfully recreated physiologically plausible collateral patterns across four clinical scenarios, encompassing mild to severe, asymmetric, and symptomatic unilateral stenosis.