Precise DCE-MRI in Diagnosing Participants With Recurrent High Grade Glioma or Melanoma Brain Metastases

Inclusion Criteria:

* COHORT I: Recurrent high-grade glioma (often with thin areas of enhancement) treated with bevacizumab.
* COHORT I: We will include adult patients with histopathologically confirmed high-grade glioma with evidence of tumor progression at baseline MRI who will undergo treatment with an anti-angiogenic agent (bevacizumab) with or without concomitant chemotherapy, and Karnofsky Performance Score \> 60%.
* COHORT I: At least 30 days should have elapsed since prior therapy including surgery and temozolomide chemoradiation.
* COHORT I: Satisfactory renal, hepatic, and hematologic function is required.
* COHORT II: Melanoma brain metastases (often small and spread throughout the brain) treated with immunotherapy.
* COHORT II: We will include adult patients with a tissue-proven history of melanoma who have contrast enhancing brain masses who will undergo treatment with immunotherapy with an anti-CTLA-4 or anti-PD-1 approach (e.g. ipilimumab, pembrolizumab, or nivolumab), and Karnofsky Performance Score \> 60%.
* COHORT II: At least 30 days should have elapsed since prior therapy including surgery, stereotactic brain irradiation, and corticosteroid use.

Exclusion Criteria:

* COHORT I: Exclusion criteria include treatment with any other anti-cancer treatment, enzyme-inducing antiepileptic agents, anticoagulant treatment, pregnancy, other anti-angiogenesis therapy and prior thrombo-embolic disorders.
* COHORT I: Exclusion criteria will include the standard contraindications for MRI: 1) prior work as a machinist or metal worker, or history of metal being removed from the eyes, 2) cardiac pacemaker or internal pacing wires, 3) non-MRI compatible vena cava filter, vascular aneurysm clip, heart valve, spinal or ventricular shunt, optic implant, neuro-stimulator unit, ocular implant, or intrauterine device, or 4) claustrophobia, or uncontrollable motion disorder.
* COHORT I: Pregnant women, prisoners, and institutionalized individuals will be excluded.
* COHORT II: Exclusion criteria include treatment with any other anti-cancer treatment, and other immunotherapy exclusion criteria.
* COHORT II: Non-cutaneous melanomas will be excluded.
* COHORT II: Exclusion criteria will include the standard contraindications for MRI: 1) prior work as a machinist or metal worker, or history of metal being removed from the eyes, 2) cardiac pacemaker or internal pacing wires, 3) non-MRI compatible vena cava filter, vascular aneurysm clip, heart valve, spinal or ventricular shunt, optic implant, neuro-stimulator unit, ocular implant, or intrauterine device, or 4) claustrophobia, or uncontrollable motion disorder.
* COHORT II: Pregnant women, prisoners, and institutionalized individuals will be excluded.