A 15 minute base line MRI of the brain will be performed initially. Following that, the medication (ferumoxytol) will be injected intravenously over 3 minutes. The second MRI of the brian will obtained 24 hours later. A third MRI will be obtained also at 72 hours following the injection of medication. Then after the third MRI, ten people will be chosen randomly to start aspirin every day for three months total. The selected aspirin group will be given 3-month supply of aspirin (81 mg). The other five patients will be asked to avoid any anti-inflammatory drugs (like aspirin, Advil, ibuprofen, …) if at all possible. Following an interval of three months, a repeat MRI of the brain will be done exactly as above (a base line MRI of the brain will be done, then the medication will be injected intravenously (IV). A second MRI will be obtained 24 hours later followed by another one at 72 hours later.