Ct-scan A CT Scan is short for computerized axial tomography of the brain. It utilizes x-rays which are combined by a computer into a single picture. This process enables the physician to obtain a series of pictures of the brain without invading the brain itself. It is used primarily to rule out organic disease such as a tumor or bleeding in the brain as a cause of the headache problem. A CT Scan can be performed with or without dye. The dye may enhance the detection of a brain tumor or a blood clot. The dye is iodine based so it must be used with caution in those with allergy to these agents. It is more sensitive than MRI scans for detecting acute bleeding on the brain. However, the MRI scan is useful for looking at other brain conditions and takes pictures at different angles than the CT. The MRI does not use x-ray or iodine dye.