R Greenhalgh

Mural Inflammation in Crohn Disease: Location-Matched Histologic Validation of MR Imaging Features

PURPOSE To validate proposed magnetic resonance (MR) imaging features of Crohn disease activity against a histopathologic reference. MATERIALS AND METHODS Ethical permission was given by the University College London hospital ethics committee, and informed written consent was obtained from all participants. Preoperative MR imaging was performed in 18 consecutive patients with Crohn disease undergoing elective small-bowel resection. The Harvey-Bradshaw index, the C-reactive protein level, and disease chronicity were recorded. The resected bowel was retrospectively identified at preoperative MR imaging, and wall thickness, mural and lymph node/cerebrospinal fluid (CSF) signal intensity ratios on T2-weighted fat-saturated images, gadolinium-based contrast material uptake, enhancement pattern, and mesenteric signal intensity on T2-weighted fat-saturated images were recorded. Precise histologic matching was achieved by imaging the ex vivo surgical specimens. Histopathologic grading of acute inflammation with the acute inflammatory score (AIS) (on the basis of mucosal ulceration, edema, and quantity and depth of neutrophilic infiltration) and the degree of fibrostenosis was performed at each site, and results were compared with MR imaging features. Data were analyzed by using linear regression with robust standard errors of the estimate. RESULTS AIS was positively correlated with mural thickness and mural/CSF signal intensity ratio on T2-weighted fat-saturated images (P < .001 and P = .003, respectively) but not with mural enhancement at 30 and 70 seconds (P = .50 and P = .73, respectively). AIS was higher with layered mural enhancement (P < .001), a pattern also commonly associated with coexisting fibrostenosis (75%). Mural/CSF signal intensity ratio on T2-weighted fat-saturated images was higher in histologically edematous bowel than in nonedematous bowel (P = .04). There was no correlation between any lymph node characteristic and AIS. CONCLUSION Increasing mural thickness, high mural signal intensity on T2-weighted fat-saturated images, and a layered pattern of enhancement reflect histologic features of acute small-bowel inflammation in Crohn disease.

MR Enterographic Manifestations of Small Bowel Crohn Disease

Magnetic resonance (MR) enterography is a clinically useful technique for the evaluation of both intraluminal and extraluminal small bowel disease, particularly in younger patients with Crohn disease. MR enterography offers the advantages of multiplanar capability and lack of ionizing radiation. It allows evaluation of bowel wall contrast enhancement, wall thickening, and edema, findings useful for the assessment of Crohn disease activity. MR enterography can also depict other pathologic findings such as lymphadenopathy, fistula and sinus formation, abscesses, and abnormal fold patterns. Even subtle disease manifestations may be detected when adequate distention of the small bowel is achieved, although endoscopic and double-contrast barium small bowel techniques remain superior in the depiction of changes in early Crohn disease (eg, aphthoid ulceration). Further research will be needed to determine whether MR imaging enhancement patterns may reliably help discriminate between active and inactive disease.

Mural Crohn Disease: Correlation of Dynamic Contrast-enhanced MR Imaging Findings with Angiogenesis and Inflammation at Histologic Examination—Pilot Study

PURPOSE To determine mural perfusion dynamics in Crohn disease by using dynamic contrast material-enhanced magnetic resonance (MR) imaging and to correlate these with histopathologic markers of inflammation and angiogenesis. MATERIALS AND METHODS Ethical permission was given by the University College London Hospital ethics committee, and informed consent was obtained from all participants. Eleven consecutive patients with Crohn disease (eight female patients, three men; mean age, 39.5 years; range, 16.4-66.6 years) undergoing elective small-bowel resection were recruited between July 2006 and December 2007. Harvey-Bradshaw index, C-reactive protein (CRP) level, and disease chronicity were recorded. Preoperatively, dynamic contrast-enhanced MR imaging was performed through the section of bowel destined for resection, and slope of enhancement, time to maximum enhancement, enhancement ratio, the volume transfer coefficient K(trans), and the extracellular volume fraction v(e) were calculated for the affected segment. Ex vivo surgical specimens were imaged to facilitate imaging-pathologic correlation. Histopathologic sampling of the specimen was performed through the imaged tissue, and microvascular density (MVD) was determined, together with acute and chronic inflammation scores. Correlations between clinical, MR imaging, and histopathologic data were made by using the Kendall rank correlation and linear regression. RESULTS Disease chronicity was positively correlated with enhancement ratio (correlation coefficient, 0.82; P = .002). Slope of enhancement demonstrated a significant negative correlation with MVD (correlation coefficient, -0.86; P < .001). There was a negative correlation between CRP level and slope of enhancement (correlation coefficient, -0.77; P = .006). Neither acute nor chronic inflammation score correlated with any other parameter. CONCLUSION Certain MR imaging-derived mural hemodynamic parameters correlate with disease chronicity and angiogenesis in Crohn disease, but not with histologic and clinical markers of inflammation. Data support the working hypothesis that microvessel permeability increases with disease chronicity and that tissue MVD is actually inversely related to mural blood flow.

CT Colonography and Computer-aided Detection: Effect of False-Positive Results on Reader Specificity and Reading Efficiency in a Low-Prevalence Screening Population

PURPOSE To retrospectively evaluate the effect of increasing numbers of computer-aided detection (CAD)-generated false-positive (FP) marks on reader specificity and reporting times by using computed tomographic (CT) colonography in a low-prevalence screening population. MATERIALS AND METHODS Ethics committee approval and informed consent were obtained for this HIPAA-compliant study. Four readers each read 48 data sets (26 men, 22 women; mean age, 57 years) from a screening population (three containing polyps) without CAD application, followed by review of the CAD output and recorded findings and diagnostic confidence. The 45 data sets that were designated as normal were chosen such that 22 generated 15 or fewer FP CAD marks and 23 generated more than 15 FP CAD marks. Sensitivity, specificity, and receiver operating characteristic (ROC) curves were calculated with and without CAD. The relationships between the number of CAD FP marks and reader confidence, reporting times, and correct data set classification were analyzed by using linear and logistic regression. RESULTS Across all readers, CAD resulted in four additional FP detections. Overall reader sensitivity and specificity (6-mm polyp threshold) before and after CAD application were 0.75 (95% confidence interval [CI]: 0.43, 0.95) versus 0.83 (95% CI: 0.52, 0.98) and 0.96 (95% CI: 0.91, 0.98) versus 0.93 (95% CI: 0.88, 0.96), respectively. The area under the ROC curve increased from 0.57 (95% CI: 0.34, 0.80) to 0.61 (95% CI: 0.42, 0.80). There was no correlation between an increasing number of CAD FP marks and reader confidence (P = .71) or correct study classification (P = .23), but there was a positive correlation with CAD-assisted reading times (0.06 [95% CI: 0.02, 0.10], P = .002). CONCLUSION Increasing numbers of CAD FP marks did not adversely influence correct reader study classification or diagnostic confidence, although reporting times did increase.

Nonlaxative PET/CT colonography: feasibility, acceptability, and pilot performance in patients at higher risk of colonic neoplasia.

CT colonography without bowel preparation is a safer and better-tolerated alternative to full laxation protocols, but comparative sensitivity and specificity are potentially reduced. Uptake of 18F-FDG by colonic neoplasia is well described, and combining PET with nonlaxative CT colonography could improve accuracy. The purpose was to prospectively test the technical feasibility and acceptability of combined nonlaxative PET/CT colonography in patients at higher risk of colorectal neoplasia and to provide pilot data on diagnostic performance. Methods: Fifty-six patients (median age, 64 y; 30 women) at high risk of colonic neoplasia underwent nonlaxative PET/CT colonography with barium fecal tagging within 2 wk of scheduled colonoscopy. Colonic segmental distension was graded 1 (poor) to 3 (good). A radiologist, experienced in CT colonography, and nuclear medicine physician in consensus analyzed the datasets. The diagnostic performance for standalone CT colonography and combined PET/CT colonography was compared with the reference colonoscopy. Patient experience for 25 items (each scored from 1 to 7) pertaining to satisfaction, worry, and physical discomfort was canvassed after both PET/CT colonography and colonoscopy. Results: Distension was good in 298 of 334 segments (89%; 95% confidence interval [CI], 85%−92%). Patients experienced more physical discomfort during colonoscopy (median, 4; interquartile range [IQR], 2–7) than during PET/CT colonography (median, 5; IQR, 3–7; P = 0.03) and were more willing to undergo PET/CT colonography again (36/43 [84%; 95% CI, 73%−95%] vs. 31/43 [72%; 95% CI, 59%−86%]; P = 0.001). Twenty-one patients had 54 polyps according to colonoscopy (10 with at least 1 polyp ≥6 mm and 8 with at least 1 polyp ≥10 mm). Of 14 polyps 6 mm or greater, 12 (86%; 95% CI, 67%−100%) were 18F-FDG–avid, including all those 10 mm or greater (mean standardized uptake value, 10.1). CT colonography sensitivity for polyps 6 mm or larger was 92.9% (95% CI, 79.4%−100%) and was not improved by the addition of PET. However, combined PET/CT colonography review improved per-patient positive predictive value for a polyp 10 mm or greater from 73% (95% CI, 39–92) to 100% (95% CI, 60–100). Conclusion: In this feasibility study, simultaneous PET acquisition during nonlaxative CT colonography is technically feasible, is well tolerated, and potentially improves specificity.

Is MRI routinely indicated in pregnant patients with suspected appendicitis after equivocal ultrasound examination

A PubMed search was made using the search format illustrated in Fig. 1A. Despite adding limits to the search (Clinical Trial, Meta-Analysis, Practice Guideline, Randomized Controlled Trial, Review, Female, Humans) we were unable to reduce the search results to less than 696 papers. We, therefore, performed the search again, firstly, removing the stipulation of pregnancy and focusing on appendicitis (Fig. 1B) and then by modifying the PIO format to a ‘‘PPIO’’ format with an AND between the pregnancy and appendicitis rather than OR (Fig. 1C).