CT Scans in Children     There is increasing concern about the number of computed axial tomography (CT) scans being done in children and adolescents.     Three million CT scans per year are now performed in the United States on children. The problem seems to be that there is very little guidance on when a CT scan is truly necessary or when another type of examination will do.     Many of the CT studies are done for suspected head injuries.     The majority of children with minor head injuries turn out to be fine, meaning that too many kids are now needlessly exposed to the radiation of a CT scan.     The development of newer guidelines aims to cut by one-third the unnecessary CT scans of children's brains. CT scans do expose the patient to significant amounts of radiation, whereas MRI studies do not expose the patient to any radiation.     Children's National Medical Center in Washington, D.C. notes that CT scans are needed if children have any of the following risk factors.     1) The child is age two or younger and has a skull fracture or deformity.     2) The child has a bicycle related injury.     3) The child is dizzy, has a behavioral change or problems with vision or other senses.     4) The child scores less than 15 on a standard neurological examination called the Glasgow Coma Score.