A review of current research indicates that human brain tissue exhibits varying responses depending on the testing method used, particularly when comparing in-vivo and ex-vivo test setups. These differences highlight the necessity for a predictive computational model that can integrate and explain the diverse findings. One step in this direction involves incorporating the brain's vascular structure and associated arterial pressure into a continuum material model to more accurately represent in-vivo conditions. This integration aims to account for the interaction between solid brain tissue and fluid vascular phases, potentially clarifying the discrepancies observed between in-vivo and ex-vivo experimental results. To incorporate blood vessels into the linear (visco)elastic brain tissue model, we utilize a multiscale immersed method [1]. In this framework, blood pressure is represented by a forcing term, and a multidimensional coupling is applied through the reduced Lagrange multiplier method. Our extended model simulates the conditions of magnetic resonance elastography (MRE) testing. Previously, MRE studies have demonstrated that blood flow significantly influences in-vivo brain viscoelastic properties [2]. By comparing the parameters obtained from simulations with and without vascular integration, we can better understand the role of vasculature in brain tissue mechanics and underscore its impact on in-vivo experimental results. REFERENCES [1] L. Heltai, A. Caiazzo, and L. Müller, Multiscale Coupling of One-dimensional Vascular Models and Elastic Tissues, Annals of Biomedical Engineering, Vol. 49, pp. 3243-3254, 2021 [2] S. Hetzer, F. Dittmann, K. Bormann, S. Hirsch, A. Lipp, DJ. Wang, J. Braun and I. Sack, Hypercapnia increases brain viscoelasticity, Journal of Cerebral Blood Flow and Metabolism, Vol. 39, pp. 2445-2455, 2019