how do they perform a virtual colonoscopy

Colonoscopy Alternatives: Computed Tomography Colonography

Computed tomography colonography (CTC), also known as virtual colonoscopy, is a non-invasive medical imaging technique used to examine the large intestine (colon) for abnormalities such as polyps, tumors, and inflammatory bowel disease. It provides detailed three-dimensional images of the colon's inner lining.

Procedure Overview

The process involves two main stages: bowel preparation and image acquisition. Thorough bowel preparation is crucial to ensure clear visualization of the colon's inner surface. This typically involves a laxative regimen to cleanse the bowel of stool.

Bowel Preparation

Detailed instructions regarding diet restrictions and laxative use are provided by the physician or medical staff. The effectiveness of bowel preparation significantly impacts the quality of the images obtained.

Image Acquisition

After bowel preparation, the patient lies on a table that moves through a large, donut-shaped CT scanner. The scanner acquires a series of X-ray images from multiple angles. In some cases, a small amount of air or carbon dioxide may be introduced into the colon via a rectal catheter to distend the colon for better visualization. This minimizes the need for sedation.

Image Processing and Interpretation

The acquired images are then processed by specialized computer software to create three-dimensional reconstructions of the colon. A radiologist or gastroenterologist examines these images to identify any abnormalities or areas requiring further investigation.

Advantages

  • Non-invasive procedure requiring no incision.
  • Reduced risk of complications compared to traditional colonoscopy.
  • Better patient tolerance, often requiring less sedation or anesthesia.

Disadvantages

  • Requires thorough bowel preparation.
  • Potential for false positives or negatives; follow-up colonoscopy may be necessary.
  • Not suitable for all patients (e.g., severe bowel obstruction).
  • Radiation exposure, though generally considered low.

Polyps and Further Investigation

If polyps or other suspicious areas are detected during CTC, a traditional colonoscopy may be recommended to allow for biopsy or removal of the polyps.