What is CT or “Virtual Colonoscopy”?
Optimal performance of MDCT Colonoscopy (CTC) requires thin-section (2-3 mm) images using a low dose technique with additional dedicated CT colonography software. Typical CT scan time is 5-7 seconds and both prone and supine images are obtained. Bowel preperation requires catharisis usually with magnesium citrate or sodium phosphate. The addition of dilute 2% CT barium to tag residual stool and/or diatrizoate (gastrograffin) to opacify luminal fluid helps differentiate stool from polyps. Distension is performed with either room air or automated CO2 delivery via a small-caliber flexible catheter. Advantages over optical colonoscopy are that sedation is NOT required and other areas of the abdomen can be evaluated; however, CTC exposes the patient to radiation.
