Computed tomography (CT) colonography has gained widespread multi-disciplinary interest as
an evolving noninvasive colorectal screening examination, with the potential of improved
patient compliance. The investigator's prior work demonstrated that the bowel preparation
was the least tolerable aspect of colorectal evaluation when compared to the CT colonography
and optical colonoscopy procedures. Stool tagging could provide a more gentle and efficient
bowel preparation, with fewer false positives due to retained stool-mimicking polyps.
The researchers hypothesize that image quality and patient preference will vary with stool
tagging concentration and dosing schedule. The researchers propose to evaluate specific
stool tagging protocols with the following aims:
AIM 1: Perform a randomized trial of three specific stool tagging protocols using barium
and iodine at CT colonography in a well-characterized cohort of patients undergoing
AIM 2: Analyze the CT colonography and optical colonoscopy data to assess differences
across stool tagging protocols for the outcome measures of patient preference, image quality
in the presence of tagging, and diagnostic reader performance.
The researchers will use specific variations in stool tagging techniques to determine the
best image quality of CT data (e.g., homogenous tagging of fluid and stool), and highest
patient acceptability, as well as evaluate the adequacy of preparation for same-day
colonoscopy. Diagnostic reader performance will focus on the accuracy for detecting all
neoplastic lesions including colon cancers, adenomatous polyps, sessile adenomas and flat
adenomas. Most importantly, these results will help inform the design of a larger trial of
an optimized CT colonography technique in a community setting.
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,
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.
- Patients who are 45 to 80 years old for routine screening colonoscopy
- Patients with inflammatory bowel disease
- Patients with polyposis syndromes
- Pregnant women
- Patients over 350 pounds
- Patients with bright red blood per rectum
- Patients who have a contraindication to undergo outpatient colonoscopy, including
patients on blood thinners, prior myocardial infarction (MI) in the last six months,
history of congestive heart failure (CHF), history of arrhythmia, patients too weak
to transfer themselves from a bed to a chair, or patients with severe constipation
who would require a two day bowel preparation.
All subjects will undergo informed consent by the St. Luke’s institutional review board
(IRB). Referred subjects will be asked if they are interested in the study and those
responding affirmatively will be transferred to a recruiter to learn about the study and
begin the consent process if interested.