Mechanisms of Deep Vein Thrombosis (DVT) and Vein Wall Fibrosis

Inclusion Criteria: * Men and women * Diagnosis of a first episode of acute proximal leg DVT within 4 weeks of initial DVT diagnosis and without symptomatic pulmonary embolism (PE) * Must have ECOG performance status ≤ 2 * Expected life expectancy of \>2 years * Before initiation of anticoagulation, must have adequate platelet count: Platelet count \> 100 x 10\^9/L, * Before initiation of anticoagulation, must have adequate hemoglobin (Hgb) count: Hgb \> 9 mg/DL * Before initiation of anticoagulation, must have normal INR and PTT: INR ≤ 1.5 and aPTT≤40 Exclusion Criteria: * Concurrent participation in another therapeutic clinical trial * History of prior DVT in the previous 2 years * Recurrent deep vein thrombosis (DVT) * Established post thrombotic syndrome (PTS) * Limb-threatening circulatory compromise * Pulmonary embolism with hemodynamic compromise * Deranged baseline coagulation profile before initiation of anticoagulation: INR \> 1.5 or aPTT prolonged \>40 * Active bleeding within last 3 months * Anemia with Hemoglobin\<9 mg/dL * Thrombocytopenia with platelets \< 100,000/ml * Previously documented hypersensitivity to either the drug or excipients * Any contraindication to anticoagulation or allergy to factor V inhibitors or ferumoxytol * Any contraindication to magnetic resonance imaging (MRI) including metal implants or claustrophobia * Severe hepatic impairment as defined by Childs-Pugh Class B or C * Severe renal impairment with CrCl\<30 ml/min, * Taking any P-GP or strong CYP3A4 inhibitors or inducers * History of major bleeding including history of gastrointestinal bleeding or intracranial bleeding * Known history of bleeding diathesis * History of chronic atrial fibrillation or stroke * History of active cancer or malignancy within 1 year, * Life expectancy \<2 years. * Patients requiring emergent or urgent surgery or procedures within the first 3 months of the study that cannot be postponed will be excluded. * Patients who are breastfeeding or anticipate pregnancy * Participant is pregnant or breastfeeding * Participant is a prisoner (protected population)