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How to prepare and what to expect?
This page explains how a CT head scan works, how to prepare, how it is done, what to expect during the scan, and how to get your results.
What is a CT head scan?
A computed tomography (CT) scan uses a special X-ray machine to take detailed pictures of the body’s organs and tissues.
A CT head scan provides more details on head injuries, stroke, brain tumors, and other brain diseases than other types of X-ray. CT can also show bone, soft tissues, and blood vessels in the same pictures.
How does it work?
During the scan, you might receive contrast (X-ray dye). Contrast is a substance that makes tissues and blood vessels easy to see in the CT pictures. If you receive contrast, it will be injected into your arm vein.
During the scan, you will lie inside the CT machine. Many X-ray beams will be passed through your head as the X-ray tube revolves around you.
The machine will take pictures from many angles, forming cross-section images (slices) of your head. Your doctor will review the pictures on a computer.
How should I prepare?
- Wear comfortable, loose-fitting clothing on the day of your scan.
- Keep taking your regular medicines prescribed by your doctor.
If you take medicines for diabetes, you might have to stop taking them if you are asked not to eat before your scan. Please talk with your doctor who manages your diabetes.
- Tell the doctor or CT technologist if you have asthma or any allergies to foods or drugs.
- Women: Tell your doctor or CT technologist if there is any chance you are pregnant.
- You must remove any jewelry, hair clips, dentures, and other metal objects that could show up on the images and make them hard to read.
If you will receive contrast before your CT scan:
- You may be asked not to eat anything for 4 hours before your scan.
- You may still drink clear liquids (water, clear juices, and coffee or tea without milk) until your scan. It is important to drink a lot of fluids before and after your scan to help your kidneys flush the contrast from your body.
- Before we give you the contrast, we will ask you if you have ever had an allergic reaction to contrast or any other medicine. Contrast contains iodine, which can cause a reaction if you are allergic to iodine.
- If you have had an allergic reaction to contrast in the past, we will ask you to take medicine to prevent a reaction to the contrast before your scan.
How is the scan done?
- We will ask you questions about allergies and other things that might cause problems during the scan.
- If contrast is needed for your scan, a small intravenous (IV) catheter (tube) is placed in your arm vein. The contrast will be given to you through this tube.
- You will lie on your back on the CT table. The technologist will help you place your head in a special head-holder. This device uses soft straps to keep your head and neck in the proper position.
- The technologist will then leave the room. You will be alone in the room during the scan, but the technologist can see, hear, and speak with you through an intercom at all times.
- You will need to hold still while the table is moved into the center of the scanner. You will also need to hold still when the scans are being done so that we can get clear images.
- For the first few scans, the table will move quickly through the scanner. These first scans check the correct starting position. The table will move more slowly for the rest of the scans.
- Afterward, the technologist will review the pictures. More scans will be done if needed.
- CT exam of the head and brain can take between 2 and 20 minutes.
- Because CT uses X-rays, you may not have a family member or friend in the CT room during the exam.
- For young patients, a parent may be able to stay in the room with their child to help reduce fear and provide comfort. The parent will need to wear a lead apron to limit exposure to the radiation used in the scan.
What will I feel during the scan?
- CT scans are painless.
- You may feel some discomfort from having to stay still.
If contrast is used:
- You may feel discomfort at the injection site.
- You may notice a warm, flushed sensation during the injection. You may also notice a metallic taste in your mouth. These reactions are normal. They should go away within 1 to 2 minutes.
- Once in a while, a patient will develop itching and hives for up to a few hours after the injection. This can be relieved with medicine.
- If you start to feel light-headed or short of breath, tell us right away. You may be having an allergic reaction to the contrast. A doctor or nurse will be nearby during the scan to help you, if needed.
- Drink plenty of fluids in the first few hours after the scan to help flush the contrast out of your system.
Who interprets the results and how do I get them?
A radiologist skilled in CT scanning will review and interpret the CT images. The radiologist will not talk with you about the results. The radiologist will send a detailed report to your primary care provider or referring doctor, who will give you the results.