Aspiration thrombectomy is the standard of care for acute ischemic stroke. Successful thrombectomy includes complete removal of the clot without fragmentation into new vascular territories. A challenge in this technique is vessel collapse caused by high suction pressure, often requiring multiple aspiration passes. Additionally, while the quality of the collateral blood vessel network is positively correlated to stroke treatment outcome, its influence on the efficacy of aspiration thrombectomy has not been previously studied. This study introduces a lumped parameter (0D) blood flow solver capable of modelling arterial collapse as observed in experiments [1]. Using the constrained constructive optimization algorithm, cerebral arterial trees segmented from magnetic resonance angiography images were extended to generate four networks with varying levels of collateralization, comprising of ~100,000 blood vessels. Simulations were performed for 16 variants of the Circle of Willis. With an occlusion in the M1 or M3 segment of the Left Middle Cerebral Artery, treatment scenarios with catheters inserted at three locations for the M1 occlusion and eight locations for the M3 occlusion with or without a proximal balloon were analysed. Aspiration success was defined by three criteria: the pulling force on the occlusion exceeding a threshold (F_thresh), the blood flow rate through the aspiration catheter remaining below a fraction (Q_thresh) of the total cerebral blood flow rate, and the artery at the catheter tip not collapsing. Treatment scenarios with proximal balloons demonstrated higher success rates than those without balloons, with success improving as the catheter was positioned closer to the occlusion (Fig. 1). Additionally, the success rate increased with a reduction in F_thresh or an increase in Q_thresh. This study presents a methodology for evaluating the outcomes of various aspiration thrombectomy strategies. However, clot mechanical properties were not included, assuming the clot remained fixed and unaffected by the hemodynamic forces. REFERENCES [1] Roselli, R. J., and Diller, K. R., 2011, Biotransport: Principles and Applications, Springer New York, New York, NY. https://doi.org/10.1007/978-1-4419-8119-6.