Utility of intravenously administered contrast material at CT colonography.

PURPOSE: To determine if intravenously administered contrast material improves overall reader confidence in the assessment of the colon, large-bowel wall conspicuity, and diagnostic accuracy in the detection of colorectal polyps and cancers at computed tomographic (CT) colonography. MATERIALS AND METHODS: Two hundred patients underwent CT colonography in both supine and prone positions. A five-point scale was used to assess the effect of contrast enhancement on overall reader confidence and bowel wall conspicuity. Eighty-one patients underwent CT colonography with complete colonoscopic or surgical correlation; diagnostic accuracy was compared in 48 patients who received contrast material and 33 who did not. RESULTS: Bowel preparation was ideal in 38 (19%) of 200 patients. Enhanced prone CT images had significantly better scores for reader confidence (4.9 +/- 0.1 vs 4.6 +/- 0.1, P: <.005) and bowel wall conspicuity (4.6 +/- 0.2 vs 4.2 +/- 0.2, P: <.005) compared with those of nonenhanced prone images despite no significant difference in bowel distention (3.8 +/- 0.2 vs 3.9 +/- 0. 1, P: =.8). Enhancement significantly improved the ability to depict medium (6-9-mm) polyps (75% vs 58%, P: <.05). Three large (10-19-mm) polyps were detected only with contrast enhancement; two remained submerged despite dual positioning. CONCLUSION: The use of intravenously administered contrast material significantly improved reader confidence in the assessment of bowel wall conspicuity and the ability of CT colonography to depict medium polyps in suboptimally prepared colons.

Role of virtual computed tomographic colonography in patients with colorectal cancers and obstructing colorectal lesions.

PURPOSE: The aim of this study was to assess the ability of computed tomographic colonography to diagnose colorectal masses, stage colorectal cancers, image the proximal colon in obstructing colorectal lesions, and evaluate the anastomoses in patients with previous colorectal surgery. METHODS: We prospectively performed computed tomographic colonography examinations in 34 patients (20 males; mean age, 64.2; range, 19-91 years): 20 patients had colorectal masses (defined at endoscopy as intraluminal masses 2 cm or larger), 7 patients had benign obstructing colorectal strictures, and 7 patients had a prior colorectal resection. Final tumor staging was available in all 16 patients who had colorectal cancers and 15 patients were referred after incomplete colonoscopy. The ability of computed tomographic colonography to stage colorectal cancers, identify synchronous lesions in patients with colorectal masses, and image the proximal colon in patients with obstructing colorectal lesions was assessed. RESULTS: Computed tomographic colonography identified all colorectal masses, but overcalled two masses in patients who were either poorly distended or poorly prepared. Computed tomographic colonography correctly staged 13 of 16 colorectal cancers (81 percent) and detected 16 of 17 (93 percent) synchronous polyps. Computed tomographic colonography over-staged two Dukes Stage A cancers and understaged one Dukes Stage C cancer. A total of 97 percent (87/90) of all colonic segments were adequately visualized at computed tomographic colonography in patients with obstructing colorectal lesions compared with 60 percent (26/42) of segments at barium enema (P < 0.01). Colonic anastomoses were visualized in all nine patients, but in one patient, computed tomographic colonography could not distinguish between local tumor recurrence and surgical changes. CONCLUSION: Computed tomographic colonography can accurately identify all colorectal masses but may overcall stool as masses in poorly distended or poorly prepared colons. Computed tomographic colonography has an overall staging accuracy of 81 percent for colorectal cancer and is superior to barium enema in visualizing colonic segments proximal to obstructing colorectal lesions.

Endoluminal CT colonography after an incomplete endoscopic colonoscopy.

OBJECTIVE: We evaluated the clinical usefulness of endoluminal CT colonography after an incomplete colonoscopy. SUBJECTS AND METHODS: We prospectively studied 40 patients in whom the cecum could not be reached endoscopically despite adequate bowel preparation. Endoluminal CT colonography (120 kVp, 120 mA, 3-mm collimation, pitch of 2, 1.5-mm interval reconstruction) was performed within 2 hr of incomplete colonoscopy. Two-dimensional multiplanar reformatted images and three-dimensional endoluminal images were analyzed. Twenty-six patients (65%) underwent barium enema immediately after endoluminal CT colonography. We analyzed colonic distention; duration of endoluminal CT colonography; patient tolerance; number of colonic segments seen at colonoscopy, endoluminal CT colonography, and barium enema; and reasons for incomplete colonoscopy as well as colonic and extracolonic findings. RESULTS: Duration of endoluminal CT colonography was 14.2 +/- 4.6 min (mean +/- SD). Endoluminal CT colonography was better tolerated than colonoscopy or barium enema (p < .001). Probable causes for incomplete colonoscopy were identified at endoluminal CT colonography in 74% of 40 patients. Baseline colonic distention in the region of the transverse and right colon was considered adequate before additional air insufflation; however, the addition of air significantly enhanced colonic distention throughout the entire colon (p < .001). Endoluminal CT colonography adequately revealed 96% of all colonic segments; in comparison, barium enema adequately revealed 91% of all segments (p < .05). CONCLUSION: In patients with incomplete colonoscopy, endoluminal CT colonography successfully showed the previously unrevealed colon in more than 90% of patients. Endoluminal CT colonography is a rapid, well-tolerated technique that provides clinically useful colonic and extracolonic information and should be considered for all patients who undergo incomplete colonoscopy.

Virtual colonoscopy: a gastroenterologist's perspective.

Virtual colonoscopy is an exciting new imaging technique with potential to alter current diagnostic approaches to colonic diseases, particularly colonic neoplasms. Although colonoscopy continues to offer the highest sensitivity and specificity for evaluation of the colon, virtual colonoscopy may offer greater safety, less discomfort, and consequently greater patient acceptance. In addition, virtual colonoscopy offers shorter procedure time, more accurate lesion location, and potentially lower cost as a screening test. Limited data are currently available to define virtual colonoscopy's full clinical role. This article describes the technical considerations, current clinical status, limitations, and potential indications of this new and exciting technology which gastroenterologists should not fear but embrace.

Using multimedia virtual patients to enhance the clinical curriculum for medical students.

Changes in the environment in which clinical medical education takes place in the United States has profoundly affected the quality of the learning experience. A shift to out-patient based care, minimization of hospitalization time, and shrinking clinical revenues has changed the teaching hospital or "classroom" to a degree that we must develop innovative approaches to medical education. One solution is the Virtual Patient Project. Utilizing state-of-the-art computer-based multimedia technology, we are building a library of simulated patient encounters that will serve to fill some of the educational gaps that the current health care system has created. This project is part of a newly formed and unique organization, the Harvard Medical School-Beth Israel Deaconess Mount Auburn Institute for Education and Research (the Institute), which supports in-house educational design, production, and faculty time to create Virtual Patients. These problem-based clinical cases allow the medical student to evaluate a patient at initial presentation, order diagnostic tests, observe the outcome and obtain context-sensitive feedback through a computer program designed at the Institute. Multimedia technology and authoring programs have reached a level of sophistication to allow content experts (the teaching faculty) to design and create the majority of the program themselves and to allow students to adapt the program to their individual learning needs.