Jasper Florie

Magnetic Resonance Imaging Compared With Ileocolonoscopy in Evaluating Disease Severity in Crohn’s Disease

BACKGROUND & AIMS Abdominal magnetic resonance imaging (MRI) has shown promising results in the detection of Crohns disease (CD)-related lesions. The purpose of this study was to assess the value of MRI in measuring disease activity in CD patients in comparison with ileocolonoscopy. METHODS Thirty-one patients undergoing ileocolonoscopy because of suspicion of relapsing CD underwent MRI with water as intraluminal contrast medium. At endoscopy, disease severity was graded (4-point scale), and Crohns Disease Endoscopic Index of Severity (CDEIS) was determined. Two radiologists independently interpreted the MRI scans. Radiologic grading (4-point scale) was compared with endoscopic grading of disease severity and CDEIS (overall, for all segments). Wall thickness and enhancement were compared with CDEIS. Patient experience and preference were determined. RESULTS In, respectively, 14 and 14 patients (radiologist 1) and 16 and 11 patients (radiologist 2) an exact match or 1 level of difference in grading was scored with the endoscopist. Correlation between severity rated at MRI and CDEIS was moderate to strong with r = 0.61 (P < .001) for observer 1 and r = 0.63 (P < .001) for observer 2. Per segment, best correlation was seen in the terminal ileum (r = 0.63; P < .001, for both observers). Wall thickness correlated moderately to strongly with CDEIS (r = 0.57, P < .001 and r = 0.50, P < .001 for observers 1 and 2), whereas enhancement correlated weakly to moderately (r = 0.45, P < .001 and r = 0.42, P < .001). Patients experienced more pain during endoscopy, and all patients except 2 preferred MRI to endoscopy. CONCLUSION MRI can correctly identify disease severity in patients with CD and is a patient-friendly alternative to ileocolonoscopy.

Computed Cleansing for Virtual Colonoscopy Using a Three-Material Transition Model

Virtual colonoscopy is a non-invasive technique for the detection of polyps. Currently, a clean colon is required; as without cleansing the colonic wall cannot be segmented. Enhanced bowel preparation schemes opacify intraluminal remains to enable colon segmentation. Computed cleansing (as opposed to physical cleansing of the bowels) allows removal of tagged intraluminal remains. This paper describes a model that allows proper classification of transitions between three materials: gas, tissue and tagged intraluminal remains. The computed cleansing effectively detects and removes the remains from the data. Inspection of the ‘clean’ wall is possible using common surface visualization techniques.

Feasibility of evaluating Crohn's disease activity at 3.0 Tesla

To determine whether abdominal 3.0T MRI can be used for evaluation of Crohns disease (CD) compared with ileocolonoscopy (CS), and to determine patient preference for MRI as opposed to CS.

Image Quality and Patient Acceptance of Four Regimens with Different Amounts of Mild Laxatives for CT Colonography

OBJECTIVE The purpose of our study was to prospectively evaluate image quality and patient acceptance of CT colonography (CTC) with fecal tagging using different levels of catharsis. SUBJECTS AND METHODS Forty consecutive increased-risk patients were randomized. Group 1 received orally 20 mg of bisacodyl, group 2 received 30 mg of bisacodyl, group 3 received 20 mg of bisacodyl and 8.2 g of magnesium citrate, and group 4 received 30 mg of bisacodyl and 16.4 g of magnesium citrate. All patients used a 2-day low-fiber diet and received diatrizoate meglumine and barium for fecal tagging. One reviewer blindly scored subjective image quality (fecal tagging, amount of residual feces [liquid or solid], luminal distention, and image readability) on a 5- to 6-point scale using a 2D review technique. The mean and SD of attenuation of tagging were measured as well as the relative SD as a measure of homogeneity. Furthermore, patient acceptance (burden related to diarrhea, abdominal pain, flatulence, and overall burden) was evaluated. Ordinal regression, generalized estimating equations, and parametric and nonparametric tests were used for analysis. RESULTS Image readability was evaluated as good or excellent in all examinations except one in group 2 (nondiagnostic) and two in group 3 (moderate). Group 2 contained more feces than group 4 (p = 0.04). With regard to mean attenuation and homogeneity of tagging, no significant differences were observed between groups. Group 4 experienced more severe diarrhea than groups 1 and 2 and higher overall burden than groups 1 and 3 (p < 0.042). CONCLUSION The mildest preparation with 20 mg of bisacodyl provided good image quality of CTC images. Increasing the amount of laxatives did not improve image quality or tagging characteristics but was associated with a lower patient acceptance.

Performance of radiographers in the evaluation of CT colonographic images

OBJECTIVE The purpose of this study was to compare the accuracy of radiographers with that of radiologists in the interpretation of CT colonographic images. MATERIALS AND METHODS Four observers (a radiologist, a radiologist in training, and two radiographers) evaluated 145 data sets using a primary 3D approach. The radiographers were part of our CT colonography work group and underwent training that consisted of 20 cases. The reference standard was optical colonoscopy with second-look colonoscopy for discrepant lesions > or = 10 mm in diameter. Mean sensitivities per patient and per polyp stratified for size (any size, > or = 6 mm, and > or = 10 mm) was determined for the radiologists and radiographers. Specificity was determined on a per-patient basis. RESULTS At colonoscopy in 86 of 145 patients, a total of 317 polyps were found (60 polyps > or = 6 mm in 26 patients and 31 polyps > or = 10 mm in 18 patients). No statistically significant differences were found in detection rates between radiologists and radiographers. Sensitivities for patients with a lesion of any size (66% for radiologists vs 65% for radiographers), > or = 6 mm (81% vs 87%), and > or = 10 mm (both 78%) were similar for all observers. On a per-polyp basis, detection rates were equivalent regardless of polyp size (47% vs 40%), for lesions > or = 6 mm (71% vs 65%), and for lesions > or = 10 mm (69% vs 66%). Mean specificities were similar among patients without lesions (31% vs 30%), patients without lesions > or = 6 mm (71% vs 67%), and patients without lesions > or = 10 mm (93% vs 93%). CONCLUSION Radiographers with training in CT colonographic evaluation achieved sensitivity and specificity in polyp detection comparable with that of radiologists. Radiographers can be considered reviewers in the evaluation of CT colonographic images.

Segmentation and size measurement of polyps in CT colonography

Virtual colonoscopy is a relatively new method for the detection of colonic polyps. Their size, which is measured from reformatted CT images, mainly determines diagnosis. We present an automatic method for measuring the polyp size. The method is based on a robust segmentation method that grows a surface patch over the entire polyp surface starting from a seed. Projection of the patch points along the polyp axis yields a 2D point set to which we fit an ellipse. The long axis of the ellipse denotes the size of the polyp. We evaluate our method by comparing the automated size measurement with those of two radiologists using scans of a colon phantom. We give data for inter-observer and intra-observer variability of radiologists and our method as well as the accuracy and precision.

Magnetic resonance colonography with limited bowel preparation: A comparison of three strategies

To prospectively compare three strategies of magnetic resonance colonography (MRC) with fecal tagging.

Feasibility of using automated insufflated carbon dioxide (CO2) for luminal distension in 3.0 T MR colonography

PURPOSE Primary aim of our study was to prospectively evaluate the feasibility of automated carbon dioxide (CO(2)) delivery as luminal distending agent in 3.0T MR colonography. MATERIALS AND METHODS Rectally insufflated CO(2) was evaluated in four groups with different bowel preparation (A-D). Bowel preparation regimes were: gadolinium-based tagging (A), bowel purgation (B), barium-based tagging (C) and iodine-based tagging (D). Supine (3D)T1w-FFE and (2D)T2w-SSFSE series were acquired. Each colon was divided into six segments (cecum S1-rectum S6). Two observers independently assessed the presence of artefacts, diagnostic confidence and segmental colonic distension. Also characteristics of the residual stool (presence, composition and signal-intensity) were assessed per segment. Discomfort was assessed with questionnaires. RESULTS Fourteen healthy subjects were included. Colonic distension by means of rectally insufflated CO(2) was not associated with susceptibility artefacts. Overall image quality was affected by the presence of bowel motion-related artefacts: none of the segments in 3DT1w-series and 10/84 (12%) colon segments in 2DT2w-series were rated artefact-free by both observers. Diagnostic confidence ratings were superior for the 2DT2w-SSFSE series. Overall bowel distension was rated adequate to optimal in 312/336 (93%) colon segments. CONCLUSION MR colonography at 3.0T using carbon dioxide (CO(2)) for colonic distension is technically feasible. The presence of intraluminal CO(2) did not result in susceptibility artefacts, although overall image quality was influenced by artefacts.

Statistical models for quantifying diagnostic accuracy with multiple lesions per patient

We propose random-effects models to summarize and quantify the accuracy of the diagnosis of multiple lesions on a single image without assuming independence between lesions. The number of false-positive lesions was assumed to be distributed as a Poisson mixture, and the proportion of true-positive lesions was assumed to be distributed as a binomial mixture. We considered univariate and bivariate, both parametric and nonparametric mixture models. We applied our tools to simulated data and data of a study assessing diagnostic accuracy of virtual colonography with computed tomography in 200 patients suspected of having one or more polyps.

Influence of Tagged Fecal Material on Detectability of Colorectal Polyps at CT: Phantom Study

OBJECTIVE The purpose of this study was to determine the influence of tagged material on the minimal radiation dose needed to detect colorectal polyps at CT. MATERIALS AND METHODS The study was conducted in two phases. In the first, three experienced observers determined the visibility of sessile polyps (6 mm) at five contrast levels (300, 480, 790, and 1,040 HU and air) and five tube charge levels (10, 14, 20, 28, and 40 mAs) in an anthropomorphic phantom. Each polyp was present in one of eight possible locations. The mean tube charge threshold for 90% correct responses was determined for each contrast level. Blinded observers performed independent 2D readings. In the second phase of the study, three 150-cm virtual colons were evaluated at two contrast levels (300 and 480 HU) and at five tube charge levels between 20 and 80 mAs. The three colons contained 18 randomly located polyps. The mean tube charge threshold for 90% sensitivity was determined for each contrast level. RESULTS In the first phase of the study, the estimated tube charge thresholds for 300, 480, and 790 HU were 24.0, 16.3, and 6.2 mAs. At 1,040 HU and in air, all polyps were detected at the lowest tube charge setting (10 mAs). In the second phase, the tube charge thresholds for 90% sensitivity at 300 and 480 HU were 70 and 35 mAs, respectively. CONCLUSION If polyps are covered by fecal material, a considerably higher tube charge setting is needed for adequate visualization than is needed for polyps in a completely cleansed colon, especially when the density of the tagged residue is low.