Using Ferumoxytol-Enhanced MRI to Measure Inflammation in Patients With Brain Tumors or Other Conditions of the CNS

Inclusion Criteria: * Any patient with suspected brain tumor diagnosed by MRI * Patients undergoing neuro-imaging evaluation by the neurosurgical service for other indications (e.g. vascular malformations, traumatic brain injury, ischemic and hemorrhagic stroke, CNS infections, and neuro-degenerative diseases) Exclusion Criteria: * Informed consent cannot be obtained either from the patient or legal representative * Severe coexisting or terminal systemic disease that limits life expectancy or that may interfere with the conduct of the study * Contraindication to MRI (metal implants) * Hemosiderosis/hemochromatosis * Need for sedation or anesthesia (claustrophobia) that will not otherwise be undertaken as part of routine clinical care (e.g. routine MRI under sedation already planned) * Known hypersensitivity to Feraheme (ferumoxytol) or any of its components * Iron overload from any cause (not just hemosiderosis or hemochromatosis), even if secondary to frequent blood transfusions, severe chronic hemolysis, excess dietary or parenteral iron, or any other etiology