For certain exams, a contrast agent (or dye) is injected through a vein in your arm. Most people tolerate the contrast agent without any problems and merely feel flushed for a moment.
Since the contrast medium contains iodine, which may cause an allergic reaction in some people, you should consult with your physician regarding any existing allergies prior to the examination. Should you feel any discomfort during the examination, you can communicate this to the CT team any time. Modern scanners are equipped with an intercom system for this purpose.
During the examination, you lie on a comfortable table (usually face up). This table then slowly moves through the opening of the examination unit, called the gantry. You only need to pay attention to the instructions of the CT personnel who may, for example, request a brief breath hold or to remain motionless in certain areas.
As with conventional X-ray examinations, the acquisition of CT images is not felt at all; only a low whirring noise can be heard. The patient table moves slightly during the entire examination.
How long does a CT scan take?
There is no general answer to this question. The duration of a CT examination depends on which body regions are scanned. Although with a modern spiral CT scanner the actual images are produced within a few seconds, you should expect the examination to last approximately 15 to 30 minutes. If a contrast medium is used, the examination will take longer. You may also have to drink a contrast medium that will coat the gastrointestinal tract approximately one hour before the CT scan takes place.
How Is the CT Image or CT Scan Made?
While you are in the gantry, the X-ray system takes extremely detailed cross-sectional images of your body. Based on the data acquired, the computer then generates the so-called result images. This aids the physician in reliably and precisely visualizing, and then diagnosing, the presence or absence of disease inside the body.
The CT examination is called “scanning” by the experts. Scanning is a computer-controlled electronic procedure comparable to digital photography. Whether you call it a scan or an image, after the examination you and your physician will be able to see an extraordinarily precise image of the inside your body.
How should I prepare?
To ensure that optimal results are obtained, your cooperation is required. Please talk to the physician referring you to CT. He will give you detailed information on how to
prepare yourself for the examination.
Be sure to tell your doctor if you are pregnant. Like other X-ray examinations, CT scans should not be performed during pregnancy because of the exposure to radiation.
A few general tips:
- If you have images from previous examinations (including X-rays), please bring them with you.
- For head and neck examinations: please remove all jewelry, hairpins, eyeglasses, hearing aids and dentures or leave them at home.
- For abdominal examinations: please ask your physician how many hours prior to the examination you should refrain from eating or drinking.
- It is very important to let your physician know if you have had previous allergic reactions to a contrast medium, iodine or shellfish or if you have asthma.
- If you have diabetes or take medication: Please inform the radiologist or his team.
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