Non-invasive differentiation of brain tumors is not always definitive, and more accurate imaging assessments could inform patient management decisions. Externally actuated MRE has shown promise in biomechanical characterization of intracranial tumors.[1] Here, we present initial data on mechanical and hydrodynamical signatures of 7 patients (2 metastatic tumors, 1 meningioma, 4 glioblastoma) using low frequency IA-pMRE. Intrinsic actuation MRE generates brain tissue displacement maps from the natural cerebrovascular pulsations arising from pressure variations during the cardiac cycle. [2] A retrospectively gated phase contrast angiography sequence is used to acquire 8 displacement images across one cardiac cycle followed by a Fourier transform to extract motion at the cardiac frequency. Harmonic equations of motion and a nonlinear inversion algorithm, which assumes a poroelastic mechanical model, is used to recover the shear modulus (stiffness) and hydraulic conductivity (ease of fluid flow) of brain tissue.[3] Seven patients diagnosed with various types of brain tumors were enrolled and compared to healthy controls with no known neurological conditions. Tumor regions were segmented and compared to the background brain tissue. Regions identified as tumor consistently had higher shear modulus values than the surrounding healthy tissue. IA-pMRE is a promising technique that enables study of neurological diseases without requiring externally applied vibration traditionally used during MRE exams and can be introduced as part of standard MRI protocols. Contrast between tumor and healthy brain tissue exists, however, stiffness does not appear to differentiate tumor types (similarly to findings from externally actuated MRE studies). [1] Future work will increase the number of patients enrolled in the study and analyze other properties, for example, the hydraulic conductivity, to provide more information on the mechanical environment. [4]