Virtual Colonoscopy (CT Colonography)

General Information | Scheduling, Insurance and Preparation | What to Expect | Additional Info

General information General Information

About Virtual Colonoscopies

With virtual colonoscopy, sophisticated computer software combines the CT images to form a three dimensional image of the colon.

Colorectal cancer is the 2nd leading cause of cancer deaths. 95% of these deaths are preventable with screening. The American Cancer Society recommends that all adults over the age of 50 be screened for colorectal cancer by one of several methods, including virtual colonoscopy. These screening methods look for polyps and other indications of cancer within the colon and rectum. Currently, one-third of adults between 50 and 75 years of age do not get screened.

Virtual colonoscopy, also known as CT colonography, is a colorectal cancer screening method using a CT scan to view the inside of the colon. Sophisticated computer software combines the CT images to form a three dimensional image of the colon. The images are similar to what is seen during a conventional colonoscopy.

All methods of screening for colon cancer require a cleansing program for the colon. With virtual colonoscopy, a camera is not pushed through the colon as with a conventional colonoscopy does. Additionally, the colon does not need to be filled with liquid barium as it does with a barium enema. Consequently, a virtual colonoscopy tends to be significantly faster and more comfortable for patients than other common screening methods.

Conventional (fiber optic) colonoscopies have been considered the "gold standard" for colorectal cancer screening. Many studies have been conducted to compare the accuracy of virtual to conventional colonoscopies in finding tumors and polyps in the colon. Study results show that virtual colonoscopies are as accurate as or even exceed conventional colonoscopies at finding tumors and polyps of significant size. An additional benefit of CT colonography is that the radiologist can also see other abdominal structures in the CT scan images. This may enable him or her to identify other health problems when examining the images.

A limitation of virtual colonoscopies is that the radiologist cannot remove a polyp during the procedure. If polyps are found, the patient must undergo a conventional colonoscopy so they can be removed. Polyps are found in about 10% of the exams. Consequently, virtual colonoscopies are most appropriate for individuals who are not at high risk for colorectal cancer and not experiencing any symptoms of colorectal cancer.

Virtual Colonoscopy vs. Conventional Colonoscopy

A patient may choose to have a virtual colonoscopy over a conventional colonoscopy for the following reasons:

  • Generally more comfortable than conventional colonoscopy
  • Unable or unwilling to undergo conscious sedation for conventional colonoscopy
  • Taking anticoagulation medication
  • Had an incomplete conventional colonoscopy (occurs in 2-10% of conventional colonoscopies)
  • Have an obstruction that prevents a conventional colonoscopy

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Risks Involved in a CT Colonography

There is the risk of x-ray exposure; however, it is well below the level that generally causes adverse affects.

As with all colorectal screening methods including conventional colonoscopy, there is no guarantee that a virtual colonoscopy will identify all cancers and polyps. However, it is one of the most accurate colorectal cancer screening exams currently available.

Scheduling, Insurance and Preparation Scheduling, Insurance and Preparation

Exam Locations

A CT colonography can be done at the following Invision Sally Jobe locations in the Denver, Colorado area:

Call 720-493-3700 to schedule.


Contact your personal physician for a referral for this exam. Then call 720-493-3700 to schedule.

Insurance Coverage

Since virtual colonoscopies are a newer technique for colorectal cancer screening, they are sometimes not covered by insurance. Check with your insurance company to be sure. If your insurance company will cover the exam, please bring your insurance card with you. Invision Sally Jobe requires payment for the exam at the time it is received.

Conditions to Let Us Know About

In advance of your exam, let your scheduler or technologist know if any of the following circumstances apply to you:

  • Currently pregnant
  • Diabetes
  • Heart failure
  • Blood in stool
  • Unexplained weight loss
  • Crohn's disease
  • History of colon cancer
  • Previous colon surgery

Preparation Guidelines

Virtual colonoscopies require a colon cleansing. You must attend a preparation consultation before the exam to receive specific instructions. It is very important that all instructions are closely followed so the accuracy of the exam will not be affected.

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What to Expect What to Expect

During the Exam

A CT technologist assists a patient during a virtual colonoscopy CT scan.

Here is generally what will happen during a virtual colonoscopy:

  1. A technologist will ask you some safety questions.
  2. You will remove all metal and metallic objects, such as eyeglasses, belts, hair accessories and jewelry and change into a gown. You may use a secure locker for your personal items during your exam.
  3. You will go to the exam room. A small, lubricated tube will be gently placed approximately four inches into your rectum.
  4. The technologist will help position you on your back on the scanner table.
  5. Your colon will be slowly filled with carbon dioxide through the rectal tube.
  6. The scan will begin. You will hear normal whirring and mechanical noises as the CT scanner rotates around your body. It is extremely important not to move any part of your body during the scan to avoid blurring the images.
  7. The technologist will help re-position you on your stomach on the scanner table.
  8. A second scan will be completed.
  9. The tube will be removed.
  10. You will change back into your clothes.

This exam generally lasts about ten minutes. The technologist will not stay in the room during the scan, but you can speak with him or her throughout the exam by intercom.

After the Exam


You can return to your normal activities immediately after your exam.

Exam Results

A board-certified radiologist experienced in the interpretation of CT colonography will analyze the data and results from your exam. The results will be reported to your physician. Your physician will pass the results onto you.

During the exam, our radiologists and technologists will be happy to answer questions about the exam itself; however, they will not immediately provide you with the results of your exam.

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What to Expect Additional Information

Trial Results for CT Colonography

CT colonography, also known as virtual colonoscopy, is shown to have high accuracy in its ability to detect cancer and precancerous polyps using conventional colonoscopy as the reference standard and could serve as a primary screening option for colorectal cancer, according to the results of the American College of Radiology Imaging Network (ACRIN) National CT Colonography Trial.

The ACRIN trial, sponsored by the National Cancer Institute (NCI), was conducted by Radiology Imaging Associates (RIA) at the Invision Sally Jobe sites in partnership with Rocky Mountain Gastroenterology Associates, as well as at 14 other national sites. It is the largest multi-center study to estimate the accuracy of state-of-the art CT colonography involving 163 participants at Invision Sally Jobe and 2,600 participants total nationwide.

The results of the study were published in the September 18, 2008 New England Journal of Medicine article titled "Accuracy of CT Colonography for Detection of Large Adenomas and Cancers."

RIA's Dr. Richard Obregon, M.D., principal trial investigator at Invision Sally Jobe, said, "We are honored to be part of such a prestigious ACRIN trial team and help validate the use of CT colonography as a primary screening tool for colorectal cancer. As a pioneer in this field in the Rocky Mountain region, the Invision CT Colonography clinical team is confident these trial results will help further our efforts to educate the physician/provider community and the public about the values and benefits of CT colonography screening as an alternative to traditional colonoscopy."

"As the ACRIN patient advocate who worked with the research team and as a research advocate with C3: Colorectal Cancer Coalition, I am pleased that CT colonography can be added to the list of screening options. Having a method that is accurate and comprehensive while being minimally invasive is needed if we are to succeed in substantially reducing deaths from colorectal cancers," said Pam McAllister, Madison, Wisconsin.

Colorectal cancer is the third most frequently diagnosed cancer and the second leading cause of cancer death in men and women in the United States. Although screening recommendations vary somewhat, many recommend that adults age 50 and older in the general population receive a colonoscopy every 10 years. Yet, despite the known benefits of screening, studies indicate that the majority of Americans age 50 and older are not being screened for the disease.

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