Glioblastoma multiforme (GBM) is a highly aggressive, malignant brain tumor widely known to be hypoxic and hypoxia is an important factor in the poor response of GBM to treatment. The most common therapy for GBM is surgical excision followed by fractionated RT + chemotherapy. Still, after treatment, GBM patients only survive, on average, about 12 months. A safe, effective technology that raised tumor pO2 and could be administered during each fraction of RT should improve outcomes in GBM patients treated with RT. This proposal is directed to developing such a technology. NVX-108 is a nano-emulsion of dodecafluoropentane (DDFPe). Low doses of NVX-108 raise tumor pO2 by 400% compared to carbogen alone, reverse radiation resistance and increase survival in animals treated with RT. Tumor pO2 continues to rise for up to two hours following administration of NVX-108; the material clears from the body relatively rapidly facilitating repeat administration. NVX-108, a stable formulation of DDFPe, was previously tested as an ultrasound contrast agent (USCA) in 2,000 patients and was safe. The FDA deemed DDFPe approvable but it was never launched due to small size of USCA market. NuvOx had pre-IND meetings with the FDA; the FDA agreed that NuvOx could reference the prior studies of DDFPe in support of clinical trials of NVX-108. This proposal is designed to develop biomarker imaging that can be used to validate tumor re- oxygenation in GBM as well as to confirm efficacy in two relevant preclinical models of GBM. The data from this study will be used to support an IND in the US for a clinical trial in GBM patients treated with RT + NVX-108. The biomarker imaging method developed in this proposal will be incorporated into the study design of the clinical trial to confirm tumor re-oxygenation in the GBM patients. There are two principle objectives to this proposal: 1) to validate tumor re-oxygenation with NVX-108 with imaging biomarkers and 2) to confirm efficacy of NVX-108 + RT + carbogen in treating GBM. In the first objective we will study tumor re-oxygenation with NVX-108 in the C6 glioma model in rats and validate efficacy of TOLD MRI with 18F-EF5 PET. In the second model we will study tumor re- oxygenation with NVX-108 in the GL261 glioma mode in mice and validate TOLD with HypoxiSense fluorescence imaging and bioluminescence. In the second objective we will confirm efficacy of NVX-108 + RT + carbogen in these two GBM models. In the mouse model we will also treat animals with moderate and severe levels of tumor hypoxia. We hypothesize that NVX-108 will reverse radiation resistance regardless of the level of tumor hypoxia.