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Everything you need to know about Computed Tomography (CT) & CT Scanning

Current Clinical Concerns in CT: Results : Protocols


Virtual colonoscopy/CT of the colon


1. Do you know of any sites routinely administering IV contrast for CT colonography? Any contacts you could provide (or papers on the topic) would be very much appreciated. I hear equally good arguments for and against.

Answer: We do not routinely use IV contrast. One or 2 published articles did and found interpretation easier. I definitely agree, but we are currently not routinely using IV contrast for Virtual Colonoscopy.

2. Could you please tell me of what type of catheter you are currently using for infusion of air at Virtual Colonography, including the manufacturer and the name of the catheter.

Answer: We use a 24F Harris Flush tube (Kendall Healthcare). For inpatients who have trouble retaining the air, we use a classic barium tip with a balloon.

3. Our facility is considering doing VC's and I have been asked to research the equipment needed and reimbursements. We currently have a Sensation 16 and a Leonardo workstation. I have received a price on the software needed, but need to know how others are infusing the air. I need to know how others are infusing the air. What types of air infusion systems are people using?

Answer: We use the new colon package on the Leonardo and in my opinion it makes the best fly-through images and is easy to learn. As for putting air in the colon, we simply put a small catheter in the rectum and use a small balloon to distend the colon. This works well. We tried the CO2 pump without much success and returned it. The billing issue is tricky. Many sites charge people out of pocket $1000 to $1200 dollars, while others bill an abdominal/pelvis CT code and add a 3D charge.

4. We have a new Siemens 16. Administration would like to start offering VC. My only option for inserting CO2 seems to be inflating a barium bag and pushing the air in from the bag. Should I have any concerns with this?

Answer: We have never used it. One would recommend either a CO2 injector or use a bulb.

5. What is now considered the optimal bowel prep for VC? What dietary advice do you recommend if any?

Answer: One can use either Golytely or LoSo. We advise a low-fiber, liquid diet and encourage fluids to avoid dehydration.

6. It seems from your Baltimore Conference that you used water as an oral contrast with IV for most small bowel exams. This will enhance the wall, fill the lumen, and is better for 3D imaging. Is this also the case when pathology is questioned in the large bowel? And do you change the amount of water (1000 cc) and timing approximately (20-30 min)?

Answer: The water works great for the small bowel, but p.o. will not work for the colon. For the colon, you can use air in the virtual studies.

7. Do you advise using tagging agents for VC, and how often? Do you advise after every meal (broth)?

Answer: Yes, we routinely use a tagging agent 1 day prior to the study. We recommend drinking it with breakfast, lunch and dinner.

Morrin MM, Farrell RJ, Kruskal JB, Reynolds K, McGee JB, Raptopoulous V. Utility of IV administered contrast material at CT colonography Radiology 2000; 217: 765-771.

  • Summary: This study compared unenhanced supine colonography datasets to enhanced prone acquisitions in 81 patients with colonoscopy or surgical correlation. Results demonstrated significantly improved reader confidence for evaluating bowel wall conspicuity and detectability of medium polyps when IV contrast was administered.

Geenen RWF, Hussain SM, Cademartiri F et al. CT and MR colonography: Scanning techniques, postprocessing, and emphasis on polyp detection. Radiographics 2003; 24:e18. Published online only.

  • Summary: Both MR and CT acquisition and postprocessing techniques are addressed in this online review. The authors include data from numerous studies which have guided the development and improvement of protocols for CT and MR colonography.

Lefere PA, Gryspeerdt SS, Dewyspelaere J, Baekelandt M, Holsbeeck BG. Dietary fecal tagging as a cleansing method before CT colonography: initial results-polyp detection and patient acceptance. Radiology 2002; 224: 393-403.

  • Summary: One-hundred patients were included in this comparison of bowel preparation with and without fecal tagging. The results showed that the fecal tagging preparation resulted in more fecal residue; however, the differentiation of polyps from residue was improved. Survey of the patients demonstrated decreased discomfort and side effect with the fecal tagging protocol, and the sensitivity for polyp detection was similar between the two groups (88% FT and 85% non F-T).

Macari M, Bini EJ, Jacobs SL, Lange N, Lui YW. Filling defects at CT colonography: pseudo- and diminutive lesions (the good), polyps (the bad), flat lesions, masses, and carcinomas (the ugly). RadioGraphics 2003; 23:1073-1091.

  • Summary: This educational exhibit reviews CT data acquisition, the roles of 2D and 3D displays, and CT findings which aid in the discrimination and detection of polyps.
    In the section on technique, the authors describe three different bowel preparations.
    With respect to air insufflation, a flexible rubber catheter was used to administer room air. This review provides CME credit.


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