What is Computed Tomography (CT)?
A computed tomography (CT) scan uses X-rays to make detailed pictures of structures inside of the body.
During the test, you will lie on a table that is attached to the CT scanner, which is a large doughnut-shaped machine. The CT scanner sends X-rays through the body area being studied. Each rotation of the scanner provides a picture of a thin slice of the organ or area. All of the pictures are saved as a group on a computer. These images can be printed or burned to a CD.
In some cases, a dye called contrast material may be used. It may be put in a vein (IV) in your arm, to see those areas better. For some types of CT scans you drink the dye. The dye makes structures and organs easier to see on the CT pictures.
A CT scan can be used to study all parts of your body, such as the chest, belly, pelvis, or an arm or leg. It can take pictures of body organs, such as the liver, pancreas, intestines, kidneys, bladder, adrenal glands, lungs, and heart. It also can study blood vessels, bones, and the spinal cord.
How To Prepare
Before the CT scan, tell your doctor if you:
- Are or might be pregnant.
- Are allergic to any medicines, including iodine dyes.
- Have a heart condition, such as heart failure.
- Have diabetes or take metformin (Glucophage) for your diabetes. You may have to adjust your medicine for a day before and after the test.
- Have had kidney problems.
- Have asthma.
- Have a medical device, such as a pacemaker or an insulin pump.
- Have had multiple myeloma.
- Have had an X-ray test using barium contrast material (such as a barium enema) or have taken a medicine that contains bismuth (such as Pepto-Bismol) in the past 4 days. Barium and bismuth show up on X-ray films and make it hard to see the picture clearly.
- Become very nervous in small spaces. You need to lie still inside the CT scanner, so you may need a medicine (sedative) to help you relax.
Arrange for someone to take you home in case you get a medicine to help you relax (sedative) for the test.
If you have a CT scan of your belly, you may be asked to not eat any solid foods starting the night before your scan. For a CT scan of the belly, you may drink contrast material. For some CT scans, you may need a laxative or an enema before the test.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form.
How It Is Done
The CT scan is performed by a radiology technologist and once the scan is completed, the computer generates visual images of the area of the body that was scanned. These images can be transferred to film (hard copy) or burned to a CD. A radiologist is a physician who is specially trained to interpret images of the body. The interpretation is transmitted in the form of a report to the physician who requested the CT scan. Your physician can then discuss the results with the patient and/or family.
You may need to take off any jewelry. You will need to take off all or most of your clothes, depending on which area is studied. You may be able to wear your underwear for some scans. You will be given a gown to use during the test.
During the test, you will lie on a table that is attached to the CT scanner.
The table slides into the round opening of the scanner, and the scanner moves around your body. The table will move while the scanner takes pictures. You may hear a click or buzz as the table and scanner move. It is very important to lie still during the test.
During the test, you may be alone in the scanning room. But the technologist will watch you through a window. You will be able to talk to the technologist through a two-way intercom.
The test will take about 30 to 60 minutes. Most of this time is spent getting ready for the scan.