Monitoring Anti-angiogenic Therapy in Brain Tumors by Advanced MRI

This research study is an Imaging Study, in which investigators are examining if advanced magnetic resonance imaging (MRI) and spectroscopy (MRS) are able to predict the outcome of participants with a brain tumor (glioblastoma) treated with an anti-angiogenic treatment called Avastin (Avastin is the trade name for bevacizumab). MRI studies the tumor size and other physical aspects of a tumor and the MRS adds an additional analysis that measures the chemical changes that a tumor undergoes. This study aims to test whether addition of MRS to standard MRI testing will help better predict how a tumor is responding to therapy. The names of the study interventions involved in this study are: * MRI/MRS * Avastin Avastin works by interfering with the process of new blood vessel growth and is thus an anti-angiogenic. Avastin is approved by the U.S. Food and Drug Administration for use in Glioblastoma . The participant's treating physician may complement the Avastin treatment with chemotherapy including Temozolomide (TMZ) or Lomustine (CCNU). Both treatments are approved by the U.S. Food and Drug Administration for use in Glioblastoma. The purpose of this study is to predict treatment response to anti-angiogenic therapy in brain tumor participant using advanced MRI and MRS. MRI/MRS is an FDA-approved test that uses magnets to take pictures of the brain and lets us "see inside" the body/brain without surgery.