The successful introduction of anti-angiogenic therapies into clinical trials requires the development of reliable non-invasive methods for assessing angiogenesis and its modulation or inhibition in-vivo. Thus, in the last few years, a broad range of MRI techniques have been developed to provide feedback and surrogate markers for therapeutic response including tumor blood volume, perfusion, vessel permeability, oxygenation and vessel size. These methods, aimed at the early detection of vascular changes in response to therapy, may guide patient management based on the individual response pattern. Contrast enhanced – MRI is widely established and currently is the preferred method for brain tumor assessment. However, CE-MRI does not adequately assess LEE011 disease status especially during Bevacizumab therapy for recurrent glioblastoma since recurrence is commonly associated with nonenhancement on CE-MRI. Blood oxygenation level-dependent MRI uses the paramagnetic nature of deoxygenated hemoglobin versus the diamagnetic nature oxygenated hemoglobin. Using this method, hemoglobin can serve as an endogenous contrast agent which indirectly represents changes in blood flow, volume and oxygenation. BOLD MRI is the basis for the well-established functional MRI method, in which hemodynamic changes due to neuronal activation are monitored. Changes in BOLD signal can also occur due to respiratory challenges of hyperoxia or hypercapnia. Pure oxygen inhalation causes increased blood oxygenation and reduced blood flow, while inhalation of a mixture of oxygen and CO2 has been shown to increased blood oxygenation and flow. Typically, when respiratory challenges are viewed, a T2* sequence is used. Previously, we utilized Hemodynamic Response Imaging, an fMRI method combined with hypercapnic and hyperoxic challenges for functional analysis of vessel maturation, and vessel density and functionality. Using changes in the BOLD signal induced by respiratory challenges is not limited to brain imaging and can be used as a tool for assessing the hemodynamic response in different organs and pathologies. Several animal studies were performed to estimate treatment response in liver metastases ; classify liver fibrosis ; evaluate renal perfusion and hemodynamics during acute kidney injury ; and study tumor vasculature. Also, several studies utilized rodent brain models in order to distinguish neural from non-neural contributions to fMRI signals and evaluated BOLD signal changes due to hyperoxia and hypercapnia. Recently, our group reported a clinical study demonstrating the use of HRI for the assessment of angiogenesis in brain tumors both in untreated tumors and in tumors treated with chemotherapy and radiation therapy. The aim of the current study focused on the development of equivalent mouse model, which will enable us to perform more fundamental research in order to achieve better understanding of the involved cellular processes and to elucidate the imaging characteristics. In this context an orthotopic mouse model for brain glioblastoma tumors was established. In this model, the effect of an anti-angiogenic treatment with B20-4.1.1 was evaluated.