Medical Imaging Northwest | CT (CAT Scan)

CT (CAT Scan)

What is Computed Tomography?

The computed tomography scan (also referred to as CT or CAT scan) is a sophisticated CT x-ray tube that rotates in a circle around a person taking many pictures of the body and anatomy as it rotates. The multiple images are reconstructed by a computer in axial slice images, similar to the way a loaf of bread is sliced. Each slice may then be examined separately. This modality can detect many conditions that do not show up on less sophisticated tests.

Computed tomography is a radiographic technique. While x-rays pass through the person as in standard radiography, the x-ray beam in CT is "fired" from multiple angles to generate each image. Standard x-rays are detected by film, but in CT they strike radiation detectors that produce a tiny electrical impulse proportional to the intensity of the x-ray beam. The electrical current is digitized and registered in the form of computer-stored data.

One of the advantages of CT is that computer-stored data can be recreated and manipulated with differing degrees of photographic contrast...without requiring reexamination of the person.
The data and sensitivity of the radiation detectors (as opposed to film images) result in greater sensitivity to small radiographic density changes. CT, therefore, can detect slight variations in tissue density. CT is a "non-contact" procedure and is not inhibited by surgical dressings or drains, skin lesions, or wounds.

CT may be used to check for bleeding, detect tumors, clots, ruptured disks, organ size/shape, and to evaluate a variety of disease processes.

How should I prepare?


CT appointments may be scheduled at our Puyallup, Sunrise and Bonney Lake Imaging Centers, in the Radiology Departments of our hospital locations or MultiCare partner clinic sites in Covington, Auburn, Kent, Northshore and Gig Harbor. Please allow 30-60 minutes for the examination.

If there is a chance that you may be pregnant, please inform our staff at the time you schedule your appointment.

Preparation for your CT may vary according to the type of examination performed. The Receptionist will give you instructions when your examination is scheduled.

Depending if your referring physician has ordered an examination requiring oral or IV contrast,
you may be asked to limit your food and/or liquid intake for a specified period prior to the examination.

Additionally, you may be asked to pick up a pre-examination dose of oral contrast before your appointment date. Or, you may need to arrive early the day of the exam to drink the oral contrast on site.

Wear comfortable, loose-fitting clothing the day of your CT exam. Avoid wearing any metal objects such as jewelry, hairpins, earrings, or other similar items. During the exam you will be asked to take off your glasses, hearing aids, or any removable dental work.

Also, please make arrangements to keep your children at home on the day of your appointment. There are no childcare services onsite...and due to the presence of radiation, children are not allowed to enter exam rooms during imaging procedures.

What Should I Expect?


The CT machine resembles a large standing donut (called the gantry) with a table positioned through its center. You will be asked to lie as still as possible on the table as it is moved slowly into the gantry. The gantry houses the rotating x-ray tube and detectors. You may see the CT rotating around you, and hear the CT machine make a whirring sound as it moves around your body. There is no discomfort associated with the CT scan itself.

The technologist will not be in the room with you, but she/he can see, hear, and speak to you at all times throughout the procedure.

The IV contrast is usually injected with a motor driven power injector. If the needle becomes dislodged from the vein, irritation in the skin may occur. There is also a risk of allergy to the contrast material resulting in hives, itching, wheezing, or shock. Please tell the technologist immediately if you begin to feel itchy or short of breath.

Pretreatment with Benadryl and Prednisone usually eliminates reaction in potentially allergic patients. (Read more about Contrast Agents in this procedure section of our website.)

Results are usually available 3 working days after the procedure. Please contact your referring physician for results at that time.

If you received contrast agents, you may experience nausea, headache or dizziness after the procedure is completed. It is very important to increase the amount of water you drink for a few days after the exam. Notify your personal physician or healthcare provider if your symptoms persist.

Medical Imaging Northwest is accredited by the American College of Radiology (ACR) in CT. Which locations provide this service?
  • Puyallup Imaging Center
  • Sunrise Imaging Center
  • Bonney Lake Imaging Center
  • MultiCare Good Samaritan Hospital

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