A head computed tomography (CT) scan uses many x-rays to create pictures of the head, including the skull, brain, eye sockets, and sinuses.
Brain CT; Cranial CT; CT scan - skull; CT scan - head; CT scan - orbits; CT scan - sinuses; Computed tomography - cranial; CAT scan - brain
Head CT is done in the hospital or radiology center.
You lie on a narrow table that slides into the center of the CT scanner.
While inside the scanner, the machine's x-ray beam rotates around you.
A computer creates separate images of the body area, called slices. These images can be:
Three-dimensional models of the head area can be created by stacking the slices together.
You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods.
A complete scan usually take only 30 seconds to a few minutes.
Certain CT exams require a special dye, called contrast material. It is delivered into the body before the test starts. Contrast helps certain areas show up better on x-rays.
If you weigh more than 300 pounds (135 kg), find out if the CT machine has a weight limit. Some machines do.
You will be asked to remove jewelry and may need to wear a hospital gown during the study.
The x-rays produced by the CT scan are painless. Some people may have discomfort from lying on the hard table.
Contrast material given through a vein may cause a:
This is normal and usually goes away within a few seconds.
A head CT scan is recommended to help diagnose or monitor the following conditions:
It may also be done to look for the cause of:
Abnormal results may be due to:
Risks of CT scans include:
CT scans use more radiation than regular x-rays. Having many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. You and your provider should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.
Some people have allergies to contrast dye. Let your provider know if you have ever had an allergic reaction to injected contrast dye.
In rare cases, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, tell the scanner operator right away. Scanners come with an intercom and speakers, so someone can hear you at all times.
A CT scan can reduce or avoid the need for invasive procedures to diagnose problems in the skull. This is one of the safest ways to study the head and neck.
Other tests that may be done instead of a head CT scan include:
Chernecky CC, Berger BJ. C. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. Philadelphia, PA: Elsevier Saunders; 2013:266-432.
Shaw AS, Prokop M. Computed tomography. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology. 6th ed. New York, NY: Elsevier Churchill Livingstone; 2015:chap 4.