It also can show bone, soft tissues, and blood vessels in the same images. CT of the head and brain is a patient-friendly exam that involves little radiation exposure. You should wear comfortable, loose-fitting clothing for your CT exam. No special preparation is needed for a CT scan of the head unless you are to receive a contrast agent - a substance that highlights the brain and its blood vessels and makes abnormalities easier to see.
Many contrast agents contain iodine, which can cause such a reaction in persons who are allergic.
The radiologist also should know if you have asthma, multiple myeloma , or any disorder of the heart, kidneys, or thyroid gland , or if you have diabetes - particularly if you are taking Glucophage . Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant. In some cases an alternate study will be performed to reduce or eliminate the radiation exposure to the fetus. The CT scanner is a large, square machine with a hole in the center, something like a doughnut. The patient lies still on a table that can move up or down, and slide into and out from the center of the hole.