- Health A to Z
Definition
A cranial computed tomography (CT) scan is an imaging method that uses x-rays to create cross-sectional pictures of the head, including the skull, brain, eye sockets, and sinuses.
See: Computed tomography
Alternative Names
Brain CT; Head CT; CT scan - skull; CT scan - head; CT scan - orbits; CT scan - sinuses
How the test is performed
You will be asked to lie on a narrow table that slides into the center of the CT scanner. Depending on the study being done, you may need to lie on your stomach, back, or side.
A cranial CT scan produces images from your upper neck to the top of your head.
You must be still during the exam, because movement causes blurred images. If you can't stay still, pillows or cushions may be placed around your head to hold it in place.
Once inside the scanner, the machine's x-ray beam rotates around you. (Modern "spiral" scanners can perform the exam in one continuous motion.) You may be told to hold your breath for short periods of time.
Small detectors inside the scanner measure the amount of x-rays that make it through the part of the body being studied. A computer takes this information and uses it to create several individual images, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of your head can be created by stacking the individual slices together.
Special dye, called contrast, may be used to help highlight blood vessels and look for a mass (tumor). If this is needed, the health care provider will inject the dye into a vein.
Generally, complete scans take only a few minutes. The newest multidetector scanners can image your entire body, head to toe, in less than 30 seconds.
How to prepare for the test
Usually, no preparation is needed. However, if contrast is needed, you may be asked not to eat or drink anything for 4-6 hours before the test.
Tell your health care provider if you are allergic to IV contrast.
Since x-rays have difficulty passing through metal, you will be asked to remove jewelry and wear a hospital gown during the study.
 |
Reviewer Info: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. ; ADAM Health Illustrated Encyclopedia, 12/22/2008 |
Related Learning Centers |
 |
Advertise | Terms of Use | Privacy Policy