What imaging tests are done of the brain?

• Computerized axial tomographic scan (C.T. or CAT scan) - Uses X-rays to generate an image of the brain. Doctors use CT to determine whether a stroke has occurred and to identify the type of stroke: ischemic (result of blockage) or hemorrhagic (result of bleeding). CT scanning takes from 20 minutes to an hour to complete.
  


• Magnetic resonance imaging scanning (M.R.I.) - The patient is placed in a magnetic field, causing the behavior of brain cells to change. Once the patient is in a magnetic field, the head is subjected to bursts of energy of a known frequency. The response of the brain cells to these bursts of energy is detected as signals that ultimately generate an image of the brain. MRI can give very accurate images of the brain and is used to determine the presence, location and size of aneurysms and arteriovenous malformations, which are potential sources for hemorrhagic stroke.


• Radionuclide angiography - Radioactive compounds are injected into a vein in the arm; the bloodstream then carries them toward the head. As the radioactive compound circulates in the bloodstream, it constantly emits bursts of radiation. Once the radioactive compound reaches the brain, these bursts of radiation are detected and used to form an image of the brain. This imaging procedure can show areas where the brain has been deprived of blood flow and is damaged.