Definition of Cranial CT scan:

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

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.

How the test will feel:

The x-rays produced by the CT scan are painless. Some people may have discomfort from lying on the hard table.

Contrast give through a vein may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.

Why the test is performed:

A cranial CT scan is recommended to help diagnose or monitor the following conditions:

• Abnormal development of the head or neck
• Bleeding in the brain
• Brain infection
• Brain tumor

A cranial CT may also be done to:

• Determine the cause of a headache
• Determine the cause of vision problems, muscle weakness, numbness and tingling, hearing loss, speaking difficulties, or swallowing problems
• Diagnose a new stroke
• Evaluate changes in thinking or behavior
• Evaluate injury to the head and face