Insurance Denied a Claim

Early this year I had a blow to the head with heavy object and went to urgent care. Diagnosed as a concussion and the doctor said a CT scan probably wasn’t crucial but she could order one if I wanted. I decided to do it. Well now my insurance (an employer provided PPO through Blue Cross) denied it on grounds of having a normal neurological exam therefore the scan wasn’t medically necessary. Question is will I be liable to pay the hospital for it?