CT Colonography, a rapidly evolving technique, offers a noninvasive and efficient colorectal screening examination, with the potential to improve patient compliance. However, currently it requires the bowel preparation, one of the largest barriers to colonoscopy screening. A promising new tool in CT Colonography is stool tagging, which has the potential to decrease the amount of catharsis required by patients during the bowel preparation, while decreasing the number of false positives due to the reader mistaking residual stool for polyps.

Our primary hypothesis is that image quality and patient compliance differ depending upon the tagging agent and dosing schedule. Our strategy is to vary key components of recently reported barium and iodine protocols to further optimize them and to compare our results with existing and currently aggregating data in collaboration with other investigators.

The following aims will implement this strategy:

AIM 1: Perform a randomized control trial of specific stool tagging protocols at CT Colonography in a well characterized cohort of patients undergoing colorectal evaluation.

Task 1A - Recruit a prospective cohort of 60 subjects, randomize them equally to three different stool tagging protocols, and sequentially perform CT Colonography and optical colonoscopy on them.

Task 1B - Assess image quality of CT Colonography and optical colonoscopy data by the method of bowel preparation in the first five subjects of each arm and implement specific changes, if necessary.

AIM 2: Analyze the CT Colonography and optical colonoscopy data to assess differences across study arms for the outcome measures of patient preference, image quality of tagged stool, and diagnostic reader performance.

Task 2A: Assess patient expectations regarding the bowel preparations, CT Colonography and colonoscopy before the procedures and their preferences after the procedures.

Task 2B: Evaluate image quality, in the presence of tagged stool and fluid, of both the CT data and the colonoscopy data.

Task 2C: Perform a multi-observer reader evaluation of diagnostic performance of CT Colonography and colonoscopy, compared to the enhanced reference standard of colonoscopy aided by segmental unblinding of CT results, to assess sensitivity and specificity of colorectal polyp detection.

Upon completion, the three specific variations in stool tagging techniques will be compared on homogenous density of tagging and patient acceptability to determine which protocol optimizes the trade-off. Diagnostic performance of CT and colonoscopy will be compared to the enhanced reference standard of colonoscopy aided by the segmental unblinding of CT results. Most significantly, these results may help determine an optimal tagging protocol to use for larger trials of CT Colonography implementation in community settings.