Wear loose-fitting, comfortable clothing for the test. Sometimes the CT scan technician (a person specially trained to do CT scans) may ask you to wear a hospital gown.
You also may want to avoid wearing jewelry and other metal objects. You'll be asked to take off any jewelry, eyeglasses, and metal objects that might interfere with the test.
You may be asked to remove hearing aids and dentures as well. Let the technician know if you have any body piercing on your chest.
Tell your doctor whether you're pregnant or may be pregnant. If possible, you should avoid unnecessary radiation exposure during pregnancy. This is because of the concern that radiation may harm the fetus.
You and your doctor will decide whether the benefits of a chest CT scan outweigh the possible risks to the fetus, or whether another test might be better. If you do have the chest CT scan, the technician will take extra steps to reduce the fetus' exposure to radiation.
You also should tell your doctor whether:
These factors or conditions may raise your risk of having a bad reaction to the test.
The CT scanner is a large, tunnel-like machine with a hole in the center. You'll lie on a table that goes through the hole.
Tell your doctor if you're afraid of tight or closed spaces. He or she may give you medicine to help you relax. This medicine may make you sleepy, so you'll need to arrange for a ride home after the test.
Your doctor may inject a substance called contrast dye into a vein in your arm for the test. You may feel some discomfort when the needle is inserted. As the dye is injected, you also may feel warm and have a metallic taste in your mouth. These feelings last only a few minutes.
The contrast dye highlights areas inside your chest, which helps create clearer pictures.
Your doctor may ask you to not eat or drink for a few hours before the test, especially if contrast dye is part of the test.
Some people are allergic to the contrast dye. If you have allergic symptoms, such as itching or hives, tell the technician or doctor right away. He or she can give you medicine to relieve the symptoms.
The most common type of contrast dye used in CT scans contains iodine. Let your doctor know if you're allergic to iodine.
If you're breastfeeding, ask your doctor how long you should wait after the test before you breastfeed. The contrast dye can be passed to your baby through your breast milk.
You may want to prepare for the test by pumping and saving milk for 24 to 48 hours in advance. You can bottle-feed your baby in the hours after the CT scan.
The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.