Virtual CT Colonoscopy (VCT) is a new risk free method that allows doctors to look at the colon to detect polyps and cancers. Polyps are growths in the colon that may become cancerous if not removed. Most cancers arise from a pre-existing polyp; however, most polyps are not and will never become cancers.

The VCT procedure uses the computed tomography (CT or CAT) scanner to image the colon. The images are digitally combined with “virtual reality” software and viewed 3D as a “virtual” or “fly-through” view of the internal lining of the entire colon. The patient follows a pre-defined colon cleansing prep the day before the procedure.

At the time of the exam a small rubber tube is inserted into the rectum and a controlled volume of air is gently administered to distend the empty colon to provide clear visualization of all the ridges and folds of the colon. Images are taken lying on the back, then the stomach. All the images are completed in 10-15 minutes. The images are then reviewed on a high technology computer and interpreted by the radiologist.

This is very different than either the traditional colonoscopy that uses a long optic tube (endoscope), under deep intravenous sedation, to traverse the colon or a barium enema were the colon is filled with barium and X-rays are taken to see the lining of the colon.

Why is colorectal cancer screening important?
According to the American College of Gastroenterology, cancer of the colon or rectum (colorectal cancer) is the second leading cancer in the United States, claiming 55,000 lives each year with more than 150,000 new cases diagnosed this year. 90% of the deaths could have been avoided by the use of screening tests. Colorectal cancer often develops without symptoms, and is highly curable in its early stages, making prevention and early detection of precancerous growths extremely important.

More than 60% of the population over 50 years of age, who should be screened for colorectal cancer, is not being screened. A significant reason is an individual’s reluctance to have a colonoscopy procedure performed. Although this is the traditional method of screening, it is considered physically challenging, uncomfortable and unpleasant. Virtual Colonoscopy, a procedure with many benefits, is now available in your community.

Is colorectal cancer screening painful?
When air is introduced into the colon, some patients experience minimal temporary abdominal cramping or “gas pains”. We have chosen to use carbon dioxide in place of air to minimize the duration of discomfort and achieve a greater visualization of the lining of the colon. Although medicine can be given to relax the bowel or reduce gas pains, it is rarely needed.

Who should consider VCT vs. traditional colonoscopy?
VCT is performed for screening for polyps for a person at average risk of developing colon polyps/cancer. VCT sees BOTH sides of the hundreds of mucosal folds that cannot be seen “on the way out” with colonoscopy. VCT is excellent in evaluating the ascending colon which is not completely covered in 90% of traditional colonoscopies. Elderly or infirmed patients tolerate this procedure much better with a high diagnostic accuracy for pathology relevant to this age group.

Advantages of VCT:

• Non-invasive. No chance of bowel perforation or bleeding
• No intravenous lines
• See 100% of the colon lining interior and exterior
• No monitoring vital signs
• Able to detect important conditions outside the colon
• Spot hidden polyps in complex folds
• Less vigorous bowel cleansing preparation needed
• Detect polyps 8 mm or greater with equal or better accuracy than colonoscopy
• Complete examination of the colon after failed or incomplete colonoscopy
• Less time-consuming – 10 minutes scan time, 1/2 hour appointment time
• No sedation, recovery period or driver to take you home
• Less impact on daily life – resume normal activity immediately - go to breakfast after the scan!

Disadvantages of VCT:

• Not covered by most insurance plans
• Air in the colon can cause temporary discomfort
• 15% chance of a false-positive
• No data on ability to detect superficial (flat) lesions
• May require colonoscopy for polyp removal if positive
  

What is the radiation exposure?
The dose is less than a routine abdominal CT. It is comparable to two general X-rays of the abdomen. Radiation exposure theoretically increases the risk of developing cancer, but the benefit of detecting colorectal cancer early when treatment is most effective far out weighs the risk of cumulative radiation dose that occurs every 5 to 7 years for this study.

What should I expect before or after the procedure?
To manage the prep, you can expect to stay at home the afternoon before the exam. Since sedation is not required, you are free to leave the facility and have breakfast right after the procedure is completed. You do not need to have someone accompany you to the facility or to drive you home after the procedure. There is no need for observation or recovery. You can resume all normal activities immediately. You can eat, work, or drive without delay.

How accurate is this procedure?
Neither the traditional colonoscopy nor VCT screening is 100% accurate. However, neither VCT nor colonoscopy misses important lesions in the hands of experts. There are numerous studies in the medical journals that reflect varying degrees of sensitivity and specificity. The general trend over the past few years, as technology has improved, indicates that VCT will soon become the method of choice for primary colon cancer screening.

Both screening methods missed 10-14% of polyps measuring 6mm or greater and 5% of colon cancers. Most polyps missed by VCT are small (less than 5mm) and are of little or no clinical significance. There are no published specifications for the minimal polyp size detected on VCT that should be referred for removal and what sizes should be left for surveillance. To put this into perspective, approximately 85% of all traditional colonoscopies identify no clinically significant pathology.

The goal of VCT is to increase the number of people at average risk who will be screened, and to detect and provide the traditional colonoscopy doctors more time to examine high risk patients and those with positive VCT findings. With all these advantages more people will be encouraged to take the first step towards preventing colon cancer by having a VCT colon screening performed.