A computerized tomography (CT) scan or CAT scan combines a series of X-ray images taken from different angles around your body to create cross-sectional images (slices) of the bones, blood vessels, and soft tissues inside your body. Uses computer processing. Images from a CT scan provide more detailed information than plain X-rays.
A CT scan has many uses, but it is particularly suitable for quick screening of people who may have sustained internal injuries from car accidents or other types of trauma. CT scans can be used to visualize almost all parts of the body and are used to diagnose disease or injury, as well as to plan medical, surgical, or radiation treatments.
Why it’s done
Your doctor may recommend a CT scan to help:
- Diagnose muscle and bone disorders such as bone tumors and fractures
- Indicate the location of a tumor, infection, or blood clot
- Prescribe procedures such as surgery, biopsy, and radiation therapy
- Detect and monitor diseases and conditions such as cancer, heart disease, lung lump and liver mass
- Monitor the effectiveness of certain treatments, such as cancer treatments
- Detect internal injuries and internal bleeding
Risks
Radiation exposure
During a CT scan, you are briefly exposed to ionizing radiation. The amount of radiation you get during a plain X-ray is greater because a CT scan collects more detailed information. The low doses of radiation used in CT scans have not been shown to cause long-term harm, although at very high doses, there may be a slight increase in your potential risk of cancer.
There are many benefits to a CT scan that outweigh any small potential risk. Doctors use the lowest possible dose of radiation to obtain the necessary medical information. Also, newer, faster machines and technologies require less radiation than before. Talk to your doctor about the benefits and risks of your CT scan.
Harm to unborn babies
Tell your doctor if you are pregnant. Although radiation from a CT scan is unlikely to hurt your baby, your doctor may recommend another type of exam, such as an ultrasound or MRI, to rule out radiation exposure to your baby. At the low doses of radiation used in CT imaging, no negative effects have been observed in humans.
Reactions to contrast material
In some cases, your doctor may recommend you get a special dye called a contrast material. This could be something that you are told to drink before your CT scan or something that is given through a vein in your arm or inserted into your rectum. Although rare, the contrast material can cause medical problems or allergies.
Most reactions are mild and result in a rash or itching. In rare cases, an allergic reaction can be severe, even life-threatening. Tell your doctor if you have ever had a reaction to contrast material.
How you prepare
Depending on which part of your body is being scanned, you may be asked to:
- Take off some or all of your clothes and put on a hospital gown
- Remove metal objects, such as belts, jewelry, prostheses, and glasses, that may interfere with image results
- Refrain from eating or drinking for a few hours before your scan
Contrast material
Some CT scans require a special dye called contrast material to highlight the areas of your body that are being examined. Contrast material blocks X-rays and appears white on images, which can help emphasize blood vessels, intestines, or other structures.
Contrast material can be given to you:
- By Mouth. If your esophagus or stomach is being scanned, you may need to swallow a liquid that contains contrast material. This drink can taste unpleasant.
- By Injection. Contrast agents may be injected through a vein in your arm to help your gallbladder, urinary tract, liver or blood vessels stand out on the images. You may experience warmth or a metallic taste in your mouth during the injection.
- By Enema. Contrast material may be inserted into your rectum to help visualize your bowels. This procedure can make you feel bloated and uncomfortable.
Preparing your child for the scan
If your baby or child is having a CT scan, the doctor may prescribe a sedative to keep your baby calm and stable. Movement blurs images and can give inaccurate results. Ask your doctor how to prepare your baby.
What you can expect
You can get a CT scan done in a hospital or outpatient facility. CT scans are painless and, with the new machines, take only a few minutes. The whole process usually takes about 30 minutes.
During the procedure
CT scanners are shaped like a large donut standing on its side. You lie down on a narrow, motorized table that slides through an opening in a tunnel. Straps and pillows may be used to help you stay in position. During a head scan, a special cradle may be fitted to the table that keeps your head still.
While the table leads you to the scanner, the detector and X-ray tube move around you. Each rotation yields multiple images of thin slices of your body. You can hear the buzzing and whistling sound.
CT scan technologist has a separate room from where they see and hear you. With the help of the intercom, you will be able to communicate with the technologist. To avoid blurring images the technologist may ask you to hold your breath at certain points.
After the procedure
You can return to your normal routine after the exam. If you were given a contrast material, you may have received special instructions. In some cases, you may be asked to wait a while before leaving to make sure you are feeling well after the test. After the scan, you will be asked to drink plenty of fluids to help your kidneys remove the contrast material from your body.
Results
CT images are stored as electronic data files and are usually reviewed on a computer screen. A radiologist interprets these images and sends a report to your doctor.
