Investigation of Cerebral Hemodynamics During Endovascular Aspiration: Development of an Experimental and Numerical Setup

Abstract

Purpose Acute ischemic stroke is a life-threatening emergency caused by an occlusion of a cerebral artery through a blood clot. Aspiration thrombectomy is an endovascular therapy for the removal of vessel occlusions. However, open questions regarding the hemodynamics during the intervention remain, motivating investigations of blood flow within cerebral arteries. In this study, we present a combined experimental and numerical approach to analyze hemodynamics during endovascular aspiration. Methods We have developed an in vitro setup for investigations of hemodynamic changes during endovascular aspiration within a compliant model of patient-specific cerebral arteries. Pressures, flows, and locally resolved velocities were obtained. In addition, we established a computational fluid dynamics (CFD) model and compared the simulations during physiological conditions and in two aspiration scenarios with different occlusions. Results Flow redistribution within cerebral arteries after ischemic stroke is strongly dependent on the severity of the occlusion and on the volume flow extracted by endovascular aspiration. Numerical simulations exhibit an excellent correlation of R = 0.92 for flow rates and a good correlation of R = 0.73 for pressures. Further on, the local velocity field inside the basilar artery had a good agreement between CFD model and particle image velocimetry (PIV) data. Conclusion The presented setup allows for in vitro investigations of artery occlusions and endovascular aspiration techniques on arbitrary patient-specific cerebrovascular anatomies. The in silico model provides consistent predictions of flows and pressures in several aspiration scenarios.

Collateral flow and pulsatility during large vessel occlusions: insights from a quantitative in vitro study

“…Flow shifting toward the contralateral side of the occluded M1 segment is in line with findings of an in vitro study on a complete CoW phantom ( Fahy et al, 2015 ). However, tCBF is reduced by the occlusion, confirming previous observations in a setup with the aortic bypass flow ( Luisi et al, 2023 ). In case of the left M1 occlusion, a path to the anterior circulation leads through the LACA A1 segment, rerouting the carotid flow to the anterior circulation and increasing it by approximately 30%.…”

“…The physiological blood flow in the cerebral arteries is pulsatile and described by the PI values ( Correia de Verdier and Wikström, 2016 ; Zarrinkoob et al, 2016 ), which are met by the experimental values, except for the higher LICA flow PI value. The velocity field acquired by PIV had an equidistant vector spacing of 0.07 mm through a drastically increased spatial resolution compared to a previous in vitro study ( Luisi et al, 2023 ), allowing for reliable flow quantification inside the LPComA with at least 20 velocity vectors along the vessel diameter. We obtained stable and repeatable conditions proven by low standard deviations for MAP, pulse pressure, mean flows, and PI (see Table 2 ).…”

“…For this study, we synchronized the non-invasive PIV technique to a circulatory loop in order to gain quantitative details of the communicating flow in a cerebrovascular phantom over the cardiac cycle for a physiological reference case and during three common large vessel occlusion cases. The feasibility of both generating physiological conditions in the cerebral circulation and performing PIV measurements within is explained in Luisi et al (2023) ; however, several of the stated limitations were overcome in this study through the following factors: 1. Improved robustness of the circulatory loop: stable total artificial heart and tunable aortic compliance; 2.…”

“…The model diameter of the LPComA was between 1.57 mm and 1.61 mm, while the RPComA diameter was between 1.83 mm and 1.86 mm. Instructions of the manufacturing process for creating this type of flexible and translucent anatomical phantoms were described in Luisi et al (2023) . The elasticity of the phantom material, a two-component silicone rubber (RT 625 A/B, Wacker Chemie AG, Köln, Germany), was approximately 0.53 MPa, which is determined by Young’s modulus at normal temperature and pressure, close to the result from a human MCA postmortem study (0.42 MPa) ( Chueh et al, 2009 ).…”

Generation of a Virtual Cohort of Patients for in Silico Trials of Acute Ischemic Stroke Treatments

“…For this purpose, a silicone phantom of the cerebral arteries with a complete circle of Willis anatomy was used (Figure 3A). The process of creating cerebrovascular phantoms from 3D-printed vessel lumina, which are derived from CTA scans, is described in [28].…”