(Head CT Scan, Intracranial CT Scan)

Procedure Description

What is a CT or CAT scan of the brain?

Computed tomography (CT or CAT scan) is a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than standard x-rays. CT scans also minimize exposure to radiation.

In standard x-rays, a beam of energy is aimed at the body part being studied. A plate behind the body part captures the variations of the energy beam after it passes through skin, bone, muscle, and other tissue. While much information can be obtained from a standard x-ray, a lot of detail about internal organs and other structures is not available.

In computed tomography, the x-ray beam moves in a circle around the body. This allows many different views of the same organ or structure. The x-ray information is sent to a computer that interprets the x-ray data and displays it in a two-dimensional (2D) form on a monitor. While many images are taken during a CT scan, in some cases the patient receives less radiation exposure than with a single standard x-ray.

CT scans may be done with or without “contrast.” Contrast refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your physician will notify you of this prior to the procedure.

CT scans of the brain can provide more detailed information about brain tissue and brain structures than standard x-rays of the head, thus providing more information related to injuries and/or diseases of the brain.

Other related procedures that may be used to diagnose brain disorders include x-rays, magnetic resonance imaging (MRI) of the brain, positron emission tomography (PET) scan of the brain, and angiography of the brain. Please see these procedures for additional information.

A CT scan of the brain may be performed to assess the brain for tumors and other lesions, injuries, intracranial bleeding, structural anomalies such as hydrocephalus, infections, brain function or other conditions, particularly when another type of examination such as x-rays or physical examination are not conclusive.

A CT scan of the brain may also be used to evaluate the effects of treatment on brain tumors and to detect clots in the brain that may be responsible for strokes. Another use of brain CT is to provide guidance for brain surgery or biopsies of brain tissue.

There may be other reasons for your physician to recommend a CT scan of the brain.

Risks of the Procedure

The amount of radiation used during a CT procedure is considered minimal; therefore, the risk for radiation exposure is very low.

If you are pregnant or suspect that you may be pregnant, you should notify your physician. Radiation exposure during pregnancy may lead to birth defects. If it is necessary for you to have a CT of the brain, special precautions will be made to minimize the radiation exposure to the fetus.

If contrast dye is used, there is a risk for allergic reaction to the dye. Patients who are allergic to or sensitive to medications, contrast dye, iodine, or shellfish should notify their physician.

Patients with kidney failure or other kidney problems should notify their physician. In some cases, the contrast dye can cause kidney failure, especially if the person is taking Glucophage (a diabetic medication).

There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your physician prior to the procedure.

Patient Preparation

Your physician will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.

If your procedure involves the use of contrast dye, you will be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if something is not clear.

If you are claustrophobic or tend to become anxious easily, tell your physician ahead of time, as he/she may prescribe a mild sedative for you before the procedure to make you more comfortable. It will be necessary for you to remain still and quiet during the procedure. If a sedative is given before or during the procedure, you may need to have someone drive you home afterwards.

Generally, there is no fasting requirement prior to a CT scan, unless a contrast dye is to be used. Your physician will give you special instructions ahead of time if contrast is to be used and if you will need to withhold food and drink.

Notify the technologist if you have ever had a reaction to any contrast dye, or if you are allergic to iodine or seafood.

Notify the technologist if you are pregnant or suspect you may be pregnant.

Based upon your medical condition, your physician may request other specific preparation.

During the Procedure

CT Scan

CT scans may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your physician's practices.

Generally, a CT scan of brain follows this process:

• You will be asked to remove any clothing, jewelry, hairpins, eyeglasses, hearing aids, or other metal objects that may interfere with the procedure.
• If you are asked to remove clothing, you will be given a gown to wear.
• If you are to have a procedure done with contrast, an intravenous (IV) line will be started in the hand or arm for injection of the contrast dye. For oral contrast, you will be given medication to swallow.
• You will lie on a scan table that slides into a large, circular opening of the scanning machine. Your head will be immobilized to prevent movement during the procedure.
• The technologist will be in another room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner will enable the technologist to communicate with and hear you. You will have a call button so that you can let the technologist know if you have any problems during the procedure. The technologist will be watching you at all times and will be in constant communication.
• As the scanner begins to rotate around you, low-dosage x-rays will pass through the body for short amounts of time. You will hear clicking sounds, which are normal.
• The x-rays absorbed by the body's tissues will be detected by the scanner and transmitted to the computer. The computer will transform the information into an image to be interpreted by the radiologist.
• It will be very important for you to remain very still during the procedure.
• If contrast dye is used for your procedure, you will be removed from the scanner after the first set of scans has been completed. A second set of scans will be taken after the contrast dye has been administered.
• If contrast dye is used for your procedure, you may feel some effects when the dye is injected into the IV line. These effects include a flushing sensation, a salty or metallic taste in the mouth, a brief headache, or nausea and/or vomiting. These effects usually last for a few moments.
• You should notify the technologist if you feel any breathing difficulties, sweating, numbness, or heart palpitations.
• When the procedure has been completed, you will be removed from the scanner.
• If an IV line was inserted for contrast administration, the line will be removed.
• You may be asked to wait for a short period of time while the radiologist examines the scans to make sure they are clear.
• While the CT procedure itself causes no pain, having to lie still for the length of the procedure might cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure such as surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.

After the Procedure

If contrast dye was used during your procedure, you may be monitored for a period of time for any side effects or reactions to the contrast dye, such as itching, swelling, rash, or difficulty breathing.

If you notice any pain, redness, and/or swelling at the IV site after you return home following your procedure, you should notify your physician as this could indicate an infection or other type of reaction.

Otherwise, there is no special type of care required after a CT scan of the brain. You may resume your usual diet and activities unless your physician advises you differently.

Frequently Asked Questions about CT Scans

Q. Does the test hurt?

A. Generally there is little discomfort, but if an IV is inserted for contrast administration, this may be uncomfortable.

Q. How long does the test take?

A. Usually the CT scan takes about 15 to 45 minutes.

Q. What is being evaluated in the CT scan?

A. See above discussion.

Useful Links About This Procedure

The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your physician. Please consult your physician with any questions or concerns you may have regarding your condition.

This page contains links to other Web sites with information about this procedure and related health conditions. We hope you find these sites helpful, but please remember we do not control or endorse the information presented on these Web sites, nor do these sites endorse the information contained here.

American Academy of Orthopaedic Surgeons

American Academy of Neurology

American Cancer Society

Brain Injury Association

National Cancer Institute

National Institute for Neurological Disorders and Stroke

National Institutes of Health (NIH)

National Library of Medicine

National Stroke Association