The purpose of this study is to examine the safety and feasibility of using hyperpolarized metabolic MRI to study early brain metabolism changes in subjects presenting with head injury and suspected non-penetrating traumatic brain injury (TBI). This study will also compare HP pyruvate MRI-derived metrics in TBI patients with healthy subjects as well as Subarachnoid hemorrhage (SAH) patients to better understand if metabolic Magnetic resonance imaging scan (MRI) can improve our ability to diagnose a TBI. The FDA is allowing the use of hyperpolarized \[1-13C\] pyruvate (HP 13C-pyruvate) in this study. Up to 15 patients (5 with TBI, 5 with SAH, and 5 healthy volunteers) may take part in this study at the University of Maryland, Baltimore (UMB).