Monitoring Anti-angiogenic Therapy in Brain Tumors by Advanced MRI

Inclusion Criteria: * Participants must have histologically confirmed glioblastoma and evidence of recurrence. Patients with low-grade tumors who have progressed to glioblastoma are eligible. * Participants must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded) as ≥ 10 mm. * Patients must be anti-angiogenic therapy naïve. * Age ≥18 years. We exclude children because the chances of recruiting children with recurrent glioblastoma who will be treated with bevacizumab are small. * ECOG performance status ≤2 (Karnofsky ≥60%) * Life expectancy of greater than 10 weeks. * creatinine within normal institutional limits OR * creatinine clearance ≥30 mL/min/1.73 m2 for participants with creatinine levels above institutional normal. * Participants must be able to undergo MRI scan. * Participants whose clinical care plan includes treatment with bevacizumab mono-therapy (Group I) or bevacizumab (+ cytotoxic agents Temozolomide (TMZ) or Lomustine (CCNU). * Ability to understand and the willingness to sign a written informed consent document. Exclusion Criteria: * Participants who have already received anti-VEGF or investigational anti-angiogenic therapy for glioblastoma. * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. * Pregnant women are excluded from this study because the effects of MR imaging on the fetus are unknown and gadolinium-based intravenous contrast material is not recommended for use in pregnant patients * HIV-positive participants on combination antiretroviral therapy are ineligible because of the potential for pharmacokinetic interactions with bevacizumab, Temozolomide (TMZ) or Lomustine (CCNU). * Patients who are no suitable to undergo MRI or use gadolinium contrast due to: * Claustrophobia * Presence of metallic objects or implanted medical devices in body (i.e. cardiac pacemaker, aneurysm clips, surgical clips, prostheses, artificial hearts, valves with steel parts, metal fragments, shrapnel, tattoos near the eye, or steel implants) * Sickle cell disease * Renal failure * Reduced renal function, as determined by creatinine clearance \< 30 mL/min based on a serum creatinine level obtained within 28 days prior to registration