Disclosed herein are methods that aid in the determination of whether to perform imaging, such as magnetic resonance imaging (MRI) or computerized tomography (CT) scan, on a human subject that has sustained or may have sustained an injury to the head using an early biomarker, such as ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), glial fibrillary acidic protein (GFAP), or a combination thereof. These methods involve detecting levels and changes in levels of UCH-L1 in samples taken from a human subject at time points within 24 hours after the subject has sustained or may have sustained an injury to the head.