Computed Tomography imaging, sometimes called a CT or CAT scan, is a noninvasive medical test that can help your provider diagnose and treat your specific medical condition. CT imaging combines special x-ray equipment with sophisticated computers to produce multiple images, or pictures, of the inside of the body.

What is a CT scan?

Computed Tomography imaging, sometimes called a CT or CAT scan, is a noninvasive medical test that can help your provider diagnose and treat your specific medical condition. CT scans use invisible electromagnetic waves like a standard x-ray but are more detailed. While much information can be obtained from a standard X-ray, more specific information about internal organs and other internal structures is limited. CT imaging combines special x-ray equipment with sophisticated computers to produce a series of image slices showing the topography of inside the body, in other words tomography. CT scans are also used during organ and tumor biopsies to target areas for tissue sampling and during procedures that require fluid aspiration (withdrawal) from a specific area of the body.

CT scans may be done with or without "contrast."  Currently, we use nonionic Iodinated contrast, Omnipaque. Contrast may be taken by mouth or injected into an intravenous (IV) line. CT contrast causes the particular organ or tissue under study to be seen more clearly by the radiologist, a doctor specially trained to review and interpret imaging exams.

During CT scans, the patient will lie on a table that will slide in and out of the large circular opening while an X-ray beam moves in a circle around the body. This creates 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 on a monitor. A radiologist will interpret those images and send a report to your provider.

CT Techs for Radiology

At OHSU Diagnostic Imaging Services, your care and a commitment to a positive patient experience is our highest priority. Please feel free to call with questions regarding your appointment: 503-418-0990.

CT Protocol Mediastinal Lung Image
Ambient CT unit in Radiology

OHSU CT scanners

OHSU maintains 11 CT units including a Toshiba Aquillion Vision One, a 640 slice scanner capable of volume scanning with 16cm of coverage. 

Philips iCT 256 | Philips iCT SP 128 | Philips Ingenuity 64 | Philips Brilliance 64 | Philips Brilliance 16 | Philips Gemini PET/CT | GE Discovery MI PET/CT | Toshiba Aquilion One 640 | 2 Ceretom Portable CTs

What are the risks of the procedure?

There is concern over high and prolonged radiation exposure. We routinely review and incorporate dose reduction methods in our daily practice so that you always receive the lowest possible radiation exposure. Our facility is also fully accredited by the American College of Radiology assuring that our technologists and equipment are up-to-date. Our technologists are all accredited by the American Registry of Radiologic Technologists, and our equipment is routinely inspected by both our in-house team of medical physicists and by Oregon Radiation Protection Services. You may want to discuss these risks with your provider. If you are pregnant or suspect that you may be pregnant, you should notify your provider immediately. Let your provider know if you have ever had a reaction to CT contrast, or if you have kidney problems. As with any medication, there is a risk for allergic reaction to the CT contrast. A seafood allergy is not considered to be a contraindication for iodinated CT contrast.

What should I expect during my visit?

Your appointment is unique to you. If you were not provided with a specific appointment date and time by your provider, please call us to schedule your CT exam. When you call to schedule your appointment, a scheduling professional will provide you with any preparation instructions specific to your exam. You can also obtain preparation instructions via e-mail by signing up for MyChart during your clinic visit.

On the day of your CT exam, a technologist will ask you to remove clothing, jewelry, hairpins, eyeglasses, hearing aids, or other objects that may interfere with the procedure. If you are asked to remove any clothing, you will be given a gown to wear. If your procedure requires intravenous contrast, you will have an intravenous (IV) line placed in your arm. If your procedure requires oral contrast, you will need to drink a large cup of contrast or water, slowly, over 20 minutes. You may use the restroom at any time.

You will then be asked to lie on the scanner table. The table will slide in and out of the large, circular opening of the CT scanner several times. It is important that you remain very still during the procedure and, for some exams, you may be asked to hold your breath. The CT technologist will be located just outside the scanner room, in a control room. However, patients are in constant communication with the technologist using an intercom system.

Our CT Programs

Qualifying Participant

  • Are between 50-80 years of age (50-77 for Medicare & Medicaid patients)
  • Have smoked at least 20 pack years (for example, smoking more than 1 pack per day for 20 years or 2 packs per day for 10 years)
  • Current or former smoker; if a former smoker, has quit within the past 15 years

Lung Cancer Screening is now covered by Medicare & Medicaid Oregon and most 3rd party payers.

lung cancer screening center

Lung Cancer screening can potentially detect lung cancer at an earlier stage in high-risk patients, improving the chance for cure and survival. If you are at risk for lung cancer, a simple 15-minute screening could have a big impact on your health. Studies show that regular screening can help people live longer, healthier lives. 

Exam description

CT virtual colonoscopy is a new method to evaluate the large bowel (colon) for polyps and cancers.  Polyps are small growths in the colon that may become cancerous if not removed.  CT colonoscopy uses a CT scanner and computer virtual reality software to look inside the body without inserting a long tube (conventional optical colonoscopy) into the colon and without having to fill the colon with liquid barium (barium enema).  Research has shown that CT colonoscopy is better able to see polyps than barium enema and is nearly as accurate as conventional optical colonoscopy.

Why CT colonoscopy?

Colorectal cancer is the third most common cancer found in men and women in the US.  Colon cancer can be prevented if polyps are discovered and removed early.  Tumors take years to develop.  Initially, a cell can multiply abnormally, resulting in a benign (non-cancerous) polyp, which can remain harmless for a long time before becoming an aggressive cancer.  Polyps, when detected, can be removed preventively before possible degeneration into a cancer.  Despite this, individuals at greatest risk for colorectal cancer remain largely under-screened.  This is due, in part, to poor public awareness and non-acceptance of current screening techniques.

Several tests are used to detect polyps.  Current recommendations by the American Cancer Society include an evaluation of the entire colon at the age of 50 and then every three to five years.  Currently, there are two accepted methods for seeing the entire colon: conventional optical colonoscopy and barium enema.  The sensitivity of barium enema is far from optimal and is uncomfortable for the patient.  Conventional optical colonoscopy is associated with increased risk and cost.  In addition, this test may cause injury to the colon in 1 out of 1500 patients and is unable to evaluate the entire colon in 1 out of 10 patients.  Medications given through the veins (intravenous sedation) is usually required for conventional optical colonoscopy to make the exam bearable.  Thus, patients cannot resume normal activities immediately after the test.

CT colonoscopy is a safe method to evaluate the entire colon without the need for intravenous sedation.  This test uses a standard CT scan performed with a low radiation dose protocol to generate 3D images of the colon.  Patients need to complete a cleansing preparation of the bowel before the test.  The CT colonoscopy procedure begins with a small flexible rubber tube being placed in the rectum through which air is introduced into the colon.  A CT scan is then performed while patients like comfortably on their backs.  A second scan is then performed while the patients lie on their stomach.  The total time required for the study is approximately 10-20 minutes.  Because sedation is not required, patients are free to leave the radiology department immediately without the need for observation or recovery and can resume normal activities immediately, including driving from the hospital.  A radiologist specially trained in CT colonoscopy then analyzes the CT data to detect polyps or cancer.

Content created by Fergus Coakley, M.D.

Did you know?

Sun shining on Earth for Radiology

Just by living on planet earth we are exposed to approximately 3 mSv radiation per year. Depending on the exact location some geographic regions get more some get less. A chest x-ray has a radiation dose of approximately 0.1 mSv. Low dose CT of the chest has a radiation dose of about 1 mSv; a third of the annual natural dose.