The purposes of this study are:

1. To determine the sensitivity and specificity of the Near-Infrared Spectroscopy (NIRS) measurements for identifying intracranial hematomas due to trauma.
2. To determine the reproducibility of the Near-Infrared Spectroscopy (NIRS) measurements with different operators and at different centers

The principle used in identifying intracranial hematomas with Near-infrared spectroscopy (NIRS) is that extravascular blood absorbs Near-infrared light more than intravascular blood since there is a greater (usually 10-fold greater) concentration of hemoglobin in the acute hematoma then in the brain tissue where blood is contained within vessels. Therefore, the absorbance of Near-infrared light is greater (and therefore the reflected light less) on the side of the brain containing a hematoma, than on the uninjured side.

The NIRS sensor is placed successively in the left and right frontal, temporal, parietal, and occipital areas of the head and the absorbance of light at selected wavelengths is recorded. The difference in optical density in the different areas is calculated.

Inclusion Criteria:

• Undergoing a CT scan within 12 hours of their head injury. The criteria for obtaining a CT scan will be based on the standard of care, but generally all patients with a moderate or severe head injury will receive a CT scan on admission to the hospital, and only patients who undergo a CT will be enrolled into the study. The non-contrast CT will be performed according to standard methods.

Exclusion Criteria:

• 12 hours or more since injury.
• Massive scalp lacerations, avulsions, and hematomas The limitation to injury within 12 hours is necessary because as hematoma blood is metabolized, the absorbance characteristics change.