The study looks at whether a blood test can help doctors decide if a CT scan, a special type of X-ray for the head, is needed after a mild head injury. A mild traumatic brain injury (mTBI) is when someone hits their head but doesn't have serious symptoms like passing out. The study is happening at Grady Memorial Hospital and only adults aged 18-65 can join. People who are pregnant, in jail, or have certain health issues can't take part.

Participants will have a blood sample taken when they arrive at the emergency department (ED). The doctors will either see the blood test results to decide if a CT scan is needed or not see them at all. This will help researchers understand if the blood test can reduce unnecessary CT scans, which are expensive and expose patients to radiation.

• Study includes one ED visit for a blood test.
• Some doctors will use the blood test to decide on CT scans; others will not.
• No cost to participants, but no mention of payment for joining.