Computed Tomography (CT)

CT ScannerComputed tomography (CT or CAT scan) is a noninvasive diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. National Lung Cancer PartnershipA CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than standard X-rays. Schedule your CT scan with us today: 503 418-0990.
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Ambient Experience: Serious, made less scary

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Why is environment important?

Until now, many diagnostic image scanning environments have not been welcoming or comfortable for patients, especially children. Environments can help empower, distract, calm or relax patients of all background. In some cases, Ambient Experience may be able to help hospitals reduce the number of patients who require sedation, making scanning a shorter, safer, faster and less complicated procedure.

Please call 503 498-0990 for more information on Ambient Experience. At OHSU Diagnostic Imaging Services your care and experience is our number one priority.

What is a CT Scan

Computed tomography (CT or CAT scan) is a noninvasive diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, organs, and blood vessels. CT scans are more detailed than standard X-rays. While much information can be obtained from a standard X-ray, a lot of detail about internal organs and other structures is not available. CT scans may also be used to visualize placement of needles during biopsies of abdominal organs or tumors or during aspiration (withdrawal) of fluid from the abdomen.

In computed tomography, the X-ray beam moves in a circle around the body. This allows many different views of the same organ or structure. The X-ray information is sent to a computer that interprets the X-ray data and displays it in a two-dimensional (2D) form on a monitor.

CT scans may be done with or without "contrast." Contrast refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your doctor will notify you of this prior to the procedure.

What to Expect

CT scans can be performed on an outpatient basis, unless they are part of a patient's inpatient care. Although each facility may have specific protocols in place, generally, CT scans follow this process:

  1. You will be asked to remove any clothing, jewelry, or other objects that may interfere with the procedure. Notify the technologist if you have body piercings that might interfere. If you are asked to remove clothing, you will be given a gown to wear.
  2. If your procedure involves the contrast dye, notify the technologist if you have ever had a reaction to contrast dyes or if you are allergic to iodine. You will be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if something is not clear. An intravenous (IV) line will be started in the hand or arm for injection of the contrast dye. For oral contrast, you will be given a liquid contrast preparation to swallow. In some situations, the contrast may be given rectally.
  3. The patient will lie on a scan table that slides into a large, circular opening of the scanning machine.
  4. The CT staff will be in another room where the scanner controls are located. However, the patient will be in constant sight of the staff through a window. Speakers inside the scanner will enable the staff to communicate with and hear the patient. The patient will have a call bell so that he or she can let the staff know if he or she has any problems during the procedure.
  5. As the scanner begins to rotate around the patient, X-rays will pass through the body for short amounts of time.
  6. The X-rays absorbed by the body's tissues will be detected by the scanner and transmitted to the computer.
  7. The computer will transform the information into an image to be interpreted by the radiologist.
  8. It is very important that the patient remain very still during the procedure. You may be asked to hold your breath at various times during the procedure.
  9. The technologist will be watching the patient at all times and will be in constant communication.
  10. The patient may be asked to wait for a short period of time while the radiologist examines the scans to make sure they are clear. If the scans are not clear enough to obtain adequate information, the patient may need to have additional scans performed.

While the CT procedure itself causes no pain, having to lie still for the length of the procedure might cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure such as surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.

Risks of the procedure

Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time.

If you are pregnant or suspect that you may be pregnant, you should notify your health care provider. Radiation exposure during pregnancy may lead to birth defects.

If contrast dye is used, there is a risk for allergic reaction to the dye. Patients who are allergic to or sensitive to medications should notify their doctor. Studies show that 85 percent of the population will not experience an adverse reaction from iodinated contrast; however, you will need to let your doctor know if you have ever had a reaction to contrast dyes, or kidney problems. A reported seafood allergy is not considered to be a contraindication for iodinated contrast. If you take metformin/Glucophage, or a related medication, you will be asked to stop taking the medication for at least 48 hours after the contrast is administered, as it may cause a condition called metabolic acidosis, or an unsafe change in your blood pH.

Patients with kidney failure or other kidney problems should notify their doctor. In some cases, the contrast dye can cause kidney failure, especially if the person is dehydrated or already has underlying kidney disease. The effects of kidney disease and contrast agents have attracted increased attention over the last decade, as patients with kidney disease are more prone to kidney damage after contrast exposure.

There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.

Certain factors or conditions may interfere with the accuracy of a CT scan of the abdomen. These factors include, but are not limited to, the following:

  • Metallic objects within the abdomen, such as surgical clips
  • Barium in the intestines from a recent barium study
  • Stool and/or gas in the bowel
  • Total hip replacement

After the procedure

If contrast dye was used during your procedure, you may be monitored for a period of time for any side effects or reactions to the contrast dye, such as itching, swelling, rash, or difficulty breathing.

If you notice any pain, redness, and/or swelling at the IV site after you return home following your procedure, you should notify your doctor as this could indicate an infection or other type of reaction.

If you are given contrast by mouth, you may experience diarrhea or constipation after the procedure.

Otherwise, there is no special type of care required after a CT scan of the abdomen. You may resume your usual diet and activities unless your doctor advises you differently. Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.

The content provided here is for informational purposes only, and is not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your doctor. Please consult your health care provider with any questions or concerns you may have regarding your condition.