Objectives: (Feasibility Phase) To determine the feasibility of cardiac MRI without anesthesia in the immediate post-sepsis period in children with cancer. CMR scanning will be completed within 10 days of presentation - this will allow us to ensure that possible hemodynamic or respiratory instability and renal dysfunction has resolved prior to transport to the MRI scanner during the most acute phase of illness. (Completion Phase) To estimate the frequency of subacute sepsis-associated cardiac disease, including myocardial inflammation and dysfunction, in the post-acute phase (within 10 days of presentation) of severe sepsis in children with cancer