Evaluation of Crohn disease activity with magnetic resonance imaging

Assessment of wall inflammation and fibrosis in Crohn's disease: value of T1-weighted gadolinium-enhanced MR imaging

MRI is increasingly advocated as a robust method for quantifying disease activity in Crohn's disease. In particular, T1-weighted gadolinium-enhanced imaging shows considerable promise as a marker of inflammatory activity. However, interpretation of the literature must be made with an understanding of (i) the technical limitations of T1-weighted acquisition protocols and enhancement measurements; (ii) differences in standards of reference for disease activity employed between published studies; and (iii) important underlying macro and micro vascular changes in Crohn's disease. This review will focus specifically on the value of T1-weighted gadolinium-enhanced imaging in the assessment of wall inflammation and fibrosis.

Value of T2-weighted magnetic resonance imaging in the assessment of wall inflammation and fibrosis in Crohn's disease

This review focuses specifically on the diagnostic value of T2-weighted imaging in the assessment of Crohn's disease (CD) inflammation. In general, T2-weighted imaging has been less extensively investigated than T1-weighted gadolinium-enhanced imaging, even if it may offer similar information on disease activity. Furthermore, T2-weighted imaging allows CD characterization, which is crucial in the management of the disease when differentiating intestinal edema from fibrosis. Technical aspects, morphological findings and signs of active intestinal inflammation and fibrosis detectable on T2-weighted images will be reviewed and shown. Correlation between T2-weighted imaging findings, clinical activity indexes and histopathology features will be discussed. Since T2-weighted imaging is essential in the evaluation of CD activity, it should always complement with T1-weighted imaging, although it could also be used alone in the assessment of CD.

A computer-assisted model for detection of MRI signs of Crohn's disease activity: future or fiction?

Magnetic resonance imaging is increasingly used for abdominal evaluation and is more and more considered as the optimal imaging technique for detection of mural inflammation in patients with Crohn's disease. Grading the disease activity is important in daily clinical practice to monitor the medical treatment and is assessed by evaluating different magnetic resonance imaging features. Unfortunately, only moderate interobserver agreement is reported for most of the subjective features and should be improved. A computer-assisted model for automatic detection of abnormalities, ability to grade disease severity, and thereby influence clinical disease management based on magnetic resonance imaging is missing. Recent techniques have focused on semi-automated methods for classification and segmentation of the bowel and also on objective measurement of bowel wall enhancement using absolute T1-values or dynamic contrast-enhanced imaging. This article reviews the available computerized techniques, as well as preferred developments.

Impact of magnetic resonance enterography in the management of small bowel Crohn's disease

INTRODUCTION

Magnetic resonance enterography (MRE) is a relatively new imaging modality that involves small bowel distension with orally administered fluid. Few studies have assessed its impact on patient management.

AIM

The aim of this study was to determine whether MRE influenced the management of patients with established small bowel Crohn's disease (CD).

MATERIALS AND METHODS

From a prospectively maintained database of patients with inflammatory bowel disease, we identified patients with small bowel CD who underwent MRE between January 2007 and December 2010. The results of the MRE and subsequent changes in patient management within 1 month were evaluated.

RESULTS

Thirty women and 27 men with CD were included. Seven patients (12%) had a normal MRE. Forty-two of 57 (74%) patients had a change in management, and 41/50 (82%) patients with an abnormal MRE had changes in management (P<0.0008). After MRE, 20/42 (47%) patients had surgery and 22/42 (53%) had changes in medical treatment. Patients with stricturing disease had more surgical intervention (P=0.02), and patients with active disease on MRE had more medical intervention (P=0.0001). Patients with two or more abnormalities on MRE had more surgery compared with medical therapy (P=0.02).

CONCLUSION

The majority of patients with small bowel CD had a change in management as a result of the MRE. Because of its high clinical impact on patient management, MRE should become one of the preferred methods of small bowel evaluation in CD. Specific MRE findings may help to stratify treatment options, however, further work is required to validate this.

Resistance index in mural arteries of thickened bowel wall: predictive value for Crohn disease activity assessment in pediatric patients

OBJECTIVE

To define reliable Doppler parameters in mural arteries of affected bowel loops for quantitative assessment of Crohn disease (CD) activity in pediatric population and compare Doppler parameters with Pediatric Crohn Disease Activity Index (PCDAI).

PATIENTS AND METHODS

Thirty-four pediatric patients (7 with inactive, 27 with active disease of different severity; 13 male and 21 female; mean age 13; range 7-18) with CD were prospectively evaluated by Doppler ultrasound (DUS) of affected bowel segments. Using semiquantitative color and power Doppler assessment of vascularization of thickened bowel wall and mesentery, patients were divided in four grades. Spectral measurements (peak systolic velocity (PSV), end diastolic velocity (EDV), resistance index (RI)) of mural arteries were compared with PCDAI.

RESULTS

There was a significant difference in distribution of semiquantitative color values between inactive and active group. PSV and EDV values showed no significant difference between inactive and active group, while mean RI was significantly higher in the inactive group. RI was also significantly negatively correlated with PCDAI.

CONCLUSION

Intensity of color and power Doppler signals and RI measurement of mural arteries in thickened bowel wall is linked to CD activity and therefore might be of use in pediatric patients.

Quantitative phenotyping of inflammatory bowel disease in the IL-10-deficient mouse by use of noninvasive magnetic resonance imaging

BACKGROUND

Although magnetic resonance imaging (MRI) is an increasingly used diagnostic tool in the assessment of inflammatory bowel disease (IBD) in humans, diagnosis and quantitation of intestinal inflammation in animal models of IBD still depends on ex vivo techniques. The aim of this study was to evaluate whether high-field MRI is suitable for the quantitative phenotyping of gut inflammation in a dextran sulfate sodium (DSS)-triggered interleukin (IL)10-deficient (IL-10(-/-)) mouse model of IBD, especially in longitudinal studies.

METHODS

Using colitis-susceptible and -resistant backgrounds, MRI and ex vivo analyses were applied to characterize this specific model, differentiating disease severity and time-dependent alterations. Colon wall thickness, cecum wall tissue intensity, spleen, and mesenteric lymph node (MLN) volumes were evaluated 1, 2, 4, and 12 weeks after disease onset by T2-weighted MRI. Ex vivo parameters included histology, spleen, and MLN weight and analysis of cytokine expression.

RESULTS

MRI and ex vivo determined parameters correlated well, revealing a mouse strain-specific colitis development over time with characteristics typical for the DSS model in the initial and for the IL-10(-/-) model in the chronic phase. To evaluate the use of high-field MRI for monitoring therapeutic studies, mice with a profound colitis were treated with IL-10-producing Saccharomyces boulardii and monitored by MRI.

CONCLUSIONS

MRI can be utilized to quantify colitis development in the IL-10(-/-) model of IBD. Therefore, this noninvasive technique might be highly advantageous for an individual follow-up of colitis development in chronic models of IBD, facilitating the reduction of animal numbers in this kind of research.

Imaging of pediatric patients with inflammatory bowel disease

OBJECTIVE

The goal of this review is to examine the current imaging literature and develop basic imaging guidelines for evaluation of children with inflammatory bowel disease (IBD). The three following typical clinical scenarios in the imaging evaluation of IBD are considered: patient with an initial diagnosis of suspected IBD, the goals being to determine disease extent and severity and to differentiate Crohn disease from ulcerative colitis; patient with known IBD presenting with new acute symptoms (fever, peritonitis, leukocytosis) requiring urgent evaluation; and patient with known IBD presenting with nonacute symptomatic recurrence (abdominal pain, diarrhea), the goals being to assess the efficacy of the current treatment and to evaluate the possible need for additional medical or surgical intervention.

CONCLUSION

Imaging of pediatric patients with IBD must balance considerations of diagnostic accuracy against concerns about patient exposure to ionizing radiation and tolerance of the imaging technique. The imaging modality chosen depends on the clinical presentation and expected pathologic finding.

Differences in the location and activity of intestinal Crohn's disease lesions between adult and paediatric patients detected with MRI

OBJECTIVES

To prospectively compare paediatric patients (PP) and adult patients (AP) affected by Crohn's disease (CD) in terms of the location and activity of intestinal lesions.

METHODS

Forty-three children (mean age 15 years) and 43 adults (mean age 48 years) with proven CD underwent magnetic resonance enterography (MRE) to localise lesions and detect their activity in 9 segments of the small and large bowel. The results were analysed on a per patient and per segment basis. Ileo-colonoscopy was performed in all patients. P values less than 0.05 were considered statistically significant.

RESULTS

Involvement of terminal ileum was significantly different in the two groups: observed in 100 % of AP (43/43) versus 58 % (23/43) of PP (P < 0.0001). Conversely, the colon was diseased in 84 % of PP versus 64 % of AP. In particular, left colonic segments were significantly more involved in PP (descending colon 53 % versus 21 %, P < 0.01; rectum 67 % versus 23 %, P < 0.0001; sigmoid colon 56 % versus 37 %, not significant), whereas caecal involvement was equal in both groups. In children the maximal disease activity was found in left colonic segments, whereas in adults it was in the terminal ileum.

CONCLUSIONS

MRE detected significant differences between the two populations, showing a more extensive and severe involvement of the left colon in children but the distal ileum in adults.

KEY POINTS

• MRI is useful for assessing Crohn's disease in adult and paediatric patients. • Adult and paediatric patients show different intestinal involvement on MRI. • The distal ileum is maximally involved in adults vs. the left colon in children. • The causes of the severe left colonic disease in children are unknown. • The extensive colonic involvement in children has clinical-diagnostic implications.

Magnetic resonance colonography in rats with TNBS-induced colitis: a feasibility and validation study

BACKGROUND

Magnetic resonance colonography (MRC) has been recently developed to assess bowel inflammation in inflammatory bowel disease (IBD) patients. Evaluating animal models of inflammation with MRC may be important in new drug-screening processes. The aim of this study was to assess the feasibility of MRC in colitic rats and confront it with model characteristics.

METHODS

Colitis was induced by rectal injection of trinitrobenzene-sulfonic acid (TNBS) in 13 rats while six rats received the vehicle. MRC was performed at day 2. Colon inflammation and production of inflammatory mediators were evaluated. Image quality was assessed by wall and motion artifacts. MRC criteria were bowel wall thickness, wall signal intensity on T2-weighted (T2w) and T1w images, the appearance of a target sign pattern, and irregular patterns of mucosal surface.

RESULTS

MRC quality was good or excellent in 16/21 examinations with no difference between groups. Colitis rats were significantly different from controls in terms of wall thickness (P = 0.004), the appearance of a target sign pattern (P = 0.02), irregular patterns of mucosal surface (P = 0.01), and hyperintensity on T1w images (P = 0.03). All MRC criteria except maximal bowel wall thickness were associated with colon weight:length ratio and inflammatory biomarkers (all P < 0.05). Minimal bowel wall thickness and wall signal intensity on T2w images were associated with histological score (P < 0.05).

CONCLUSIONS

MRC is feasible and reliable in rats with TNBS-induced colitis. MRC criteria including colon wall thickness, wall signal intensity on T2w images, hyperintensity in T1w sequence, and the appearance of a target sign pattern may be potential targets for new IBD drugs.

Comparison of magnetic resonance enterography with endoscopy, histopathology, and laboratory evaluation in pediatric Crohn disease

BACKGROUND AND OBJECTIVE

Children with Crohn disease (CD) often undergo cross-sectional imaging during clinical evaluation. Magnetic resonance enterography (MRE) is becoming the preferred radiologic assessment due to the lack of radiation exposure; however, there are few data in children with CD comparing MRE with objective disease measures. The aim of the present study was to compare MRE with endoscopy, histopathology, and laboratory evaluation in children with CD.

METHODS

We performed an institutional review board-approved query of our prospective CD MRE database, which includes data in children with CD undergoing MRE since 2008.

RESULTS

A total of 147 MRE studies were performed in 119 different children with symptomatic CD. Of those, 53 (39.6%) MRE studies were performed at diagnosis to evaluate small bowel disease burden. A total of 117 (79.6%) MRE studies displayed active and/or chronic disease, whereas 30 (20.4%) MRE studies were normal. When compared with normal MRE studies, active inflammation on MRE was associated with a higher mean C-reactive protein (3.6 vs 1.1, P < 0.001), higher erythrocyte sedimentation rate (36 vs 22, P = 0.0.31), higher platelet value (439 vs 352, P = 0.033), and lower albumin (3.4 vs 3.7, P = 0.049). Comparison between MRE and endoscopy demonstrated excellent agreement when ulcers were present, and moderate agreement with histopathology.

CONCLUSIONS

Active inflammation on MRE is associated with higher C-reactive protein, erythrocyte sedimentation rate, platelets, and lower albumin in children with CD. MRE displays excellent agreement with endoscopic disease described by ulcers but poor agreement with mild mucosal disease described by erythema and friability. The present study adds to a growing body of evidence that MRE provides excellent assessment of inflammation and measures disease activity in CD.

Grading luminal Crohn's disease: which MRI features are considered as important?

OBJECTIVES

Magnetic resonance imaging (MRI) is increasingly used for disease activity grading in small bowel Crohn's disease. It is not known which imaging features are essential for grading. For further insight, we solicited the opinion of expert radiologists.

METHODS

A questionnaire about the grading of Crohn's disease was sent to 36 radiologists who had published on MRI grading of Crohn's disease between January 2006 and January 2010. Radiologists were asked which MRI protocol they used, how they graded luminal Crohn's disease, which features they used, how important they considered those features for grading, and which reference standards they used.

RESULTS

Twenty-four radiologists responded (66%). They used different protocols and features; most frequently T2-weighted sequences (79%) and contrast enhanced fat saturated T1-weighted sequences (83%). MR-enterography was more often used than MR-enteroclysis (88% versus 33%). Features most frequently considered important for grading were bowel wall thickness (79% of radiologists), the presence of an abscess (75%), T1 enhancement (75%), and T1 stratification (46%). Reference standards differed; most commonly (ileo-) colonoscopy (88%) or surgery (75%) were used.

CONCLUSIONS

Bowel wall thickness, abscess, T1 enhancement and T1 stratification are most often used for grading. Because of difference in grading, there is need for an international consensus on MRI grading of Crohn's disease.

Inflammatory bowel disease in children and adolescents: assessing the diagnostic performance and interreader agreement of magnetic resonance enterography compared to histopathology

RATIONALE AND OBJECTIVES

The purpose of this study was to determine the accuracy of magnetic resonance enterography (MRE) compared to histopathology in the evaluation of pediatric inflammatory bowel disease and to assess interreader reliability for image interpretation.

MATERIALS AND METHODS

All magnetic resonance enterography studies performed for known or suspected inflammatory bowel disease between July 2009 and July 2010 were retrospectively reviewed by two pediatric radiologists. Exams were evaluated for signs of enteric inflammation and extraenteric disease. A five-point, Likert-type scale was used to assess the overall likelihood of active inflammation, with scores ≥ 3 considered positive. Cohen's κ coefficient was calculated to assess interreader agreement. A subset of patients who had undergone ileocolonoscopy or surgery with confirmed histopathology within 45 days of MRE were used to assess the accuracy of MRE for detecting active inflammation in the terminal ileum and large bowel.

RESULTS

A total of 91 magnetic resonance enterography studies were reviewed. Of these, 45 had comparison histopathology within 45 days. The overall sensitivity of MRE for detecting active inflammation compared to ileocolonoscopy was 92% for both readers, while specificity was 100% for reader 1 and 75% for reader 2. Of the individual parameters evaluated, mucosal hyperenhancement and bowel wall thickening were the most sensitive indicators of active inflammation, each having sensitivity of 86% and specificity of 88%. Cohen's κ coefficient was 0.59, indicating moderate agreement between the readers.

CONCLUSIONS

MRE has high overall diagnostic accuracy for detecting active bowel inflammation in pediatric patients compared to ileocolonoscopy and demonstrates moderate interreader reliability.

Assessment of activity of Crohn's disease of the ileum and large bowel: proposal for a new multiparameter MR enterography score

PURPOSE

We evaluated the diagnostic accuracy of magnetic resonance enterography (MR-E) in assessing Crohn's disease (CD) activity by differentiating acute, chronic and remission stages of disease through a quantitative MR-E assessment.

MATERIALS AND METHODS

One hundred patients with a histological diagnosis of CD were studied with MR-E. Intestinal distension was obtained by oral administration of approximately 2 L of a polyethylene glycol solution (PEG). In all cases, the ileum and large bowel were imaged with morphological sequences (heavily T2-weighted single-shot, dual fast-field echo, balanced fast-field echo) and a postcontrast dynamic sequence (T1-weighted high-resolution isotropic volume excitation). Disease activity was assessed according to a multiparameter score (0-8) based on lesion morphology, signal intensity and contrast enhancement. MR-E findings were compared with clinical-laboratory data and disease activity indices [Crohn's Disease Activity Index (CDAI); Inflammatory Bowel Disease Questionnaire (IBDQ)]. Multiple regression analysis was performed by correlating MR-E score, CDAI and IBDQ. Frequencies were then compared using the χ (2) test.

RESULTS

MR-E identified inactive disease in 9% of cases, chronic disease in 57% and active disease in the remaining 34%. The most frequently involved bowel segment was the terminal ileum (52%). A statistically significant correlation was found between MR-E score and CDAI (R=0.86; p<0.001) and between MR-E score and IBDQ (R=-0.83; p<0.001). The most suggestive parameter for disease activity was layered bowel-wall enhancement, a finding predominantly present in patients with increased CDAI (≥ 150) and/or local complications (χ (2)=7.13; p<0.01).

CONCLUSIONS

MR-E is a noninvasive and diagnostic imaging modality for CD study and follow-up. The MR-E score proposed in this study proved to be useful in assessing disease severity and monitoring response to treatment.

Small bowel MR enterography: problem solving in Crohn's disease

Magnetic resonance enterography (MRE) is fast becoming the first-line radiological investigation to evaluate the small bowel in patients with Crohn's disease. It can demonstrate both mural and extramural complications. The lack of ionizing radiation, together with high-contrast resolution, multiplanar capability and cine-imaging make it an attractive imaging modality in such patients who need prolonged follow-up. A key question in the management of such patients is the assessment of disease activity. Clinical indices, endoscopic and histological findings have traditionally been used as surrogate markers but all have limitations. MRE can help address this question. The purpose of this pictorial review is to (1) detail the MRE protocol used at our institution; (2) describe the rationale for the MR sequences used and their limitations; (3) compare MRE with other small bowel imaging techniques; (4) discuss how MRE can help distinguish between inflammatory, stricturing and penetrating disease, and thus facilitate management of this difficult condition. Main Messages • MR enterography (MRE) is the preferred imaging investigation to assess Crohn's disease. T2-weighted, post-contrast and diffusion-weighted imaging (DWI) can be used. • MRE offers no radiation exposure, high-contrast resolution, multiplanar ability and cine imaging. • MRE can help define disease activity, a key question in the management of Crohn's disease. • MRE can help distinguish between inflammatory, stricturing and penetrating disease. • MRE can demonstrate both mural and extramural complications.

Magnetic resonance enteroclysis in patients with Crohn's disease: fat saturated T2-weighted sequences for evaluation of inflammatory activity

BACKGROUND AND AIMS

To evaluate fat saturated (fs) T2-weighted (w) fast relaxation fast spin echo (FRFSE)-sequences compared to the standard protocol with contrast agent for the evaluation of inflammatory activity in patients with Crohn's Disease (CD).

METHODS

Fourty-eight patients (male, 17; female, 33; mean age, 37 years) with suspicion of inflammatory activity in proven CD who underwent MR enteroclysis (MRE) at 1.5T (GE Healthcare) were retrospectively included. Two blinded radiologists analyzed MRE images for presence and extent of CD lesions and degree of local inflammation for fsT2-w FRFSE and contrast enhanced T1-w images (T2-activity; T1-activity; score, 1-4) in consensus. Furthermore, mural signal intensity (SI) ratios (T2-ratio; T1-ratio) were recorded. Patient based MRE findings were correlated with endoscopic (45 patients), surgical (6 patients), histopathological, and clinical data (CDAI) as a surrogate reference standard.

RESULTS

In total, 24 of 48 eligible patients presented with acute inflammatory activity with 123 affected bowel segments. ROC analysis of the total inflammatory score presented an AUC of 0.93 (p<0.001) for T2-activity (T1-activity, AUC 0.63; p=0.019). ROC analysis revealed an AUC of 0.76 (p<0.001) for the T2-ratio (T1-ratio, AUC 0.51; p=0.93). General linear regression model revealed T2-activity (p=0.001) and age (p=0.024) as predictive factors of acute bowel inflammation.

CONCLUSIONS

T2-w FRFSE-sequences can depict CD lesions and help to assess the inflammation activity, even with improved accuracy as compared to contrast-enhanced T1-w sequences.

MR enterography correlates highly with colonoscopy and histology for both distal ileal and colonic Crohn's disease in 310 patients

BACKGROUND AND AIMS

To evaluate the efficacy of MR enterography (MRE) in patients with known or suspected Crohn's disease without the use of anti-peristaltic pharmacologic agents compared to colonoscopy and histology.

METHODS

A retrospective review of 850 consecutive patients who underwent routine MRE to evaluate known or suspected Crohn's disease was performed. Of these, 310 patients also underwent colonoscopy with biopsy(s) within 90 days. The results of the MRE were compared to the colonoscopy and pathology reports to determine the presence or absence of disease in evaluable bowel segments. Individual imaging parameters (including wall thickening, enhancement, T2 signal, mesenteric vascular prominence and adenopathy) were also separately analyzed to determine their independent predictive value.

RESULTS

In 310 patients, the overall sensitivity and specificity of MRE (using endoscopy as a gold standard) were 85% and 80% respectively (kappa=0.65). The sensitivity of MRE for detection of pathologically severe disease was 87% in the terminal ileum (TI) and 88% in the colon. In the subset of 162 patients who underwent colonoscopy within 30 days of MRE, the overall sensitivity remained 85% but the specificity increased to 85% (kappa=0.69). Wall thickening and abnormal enhancement were sensitive indicators of Crohn's disease (75% and 78%), while abnormal T2 signal, mesenteric vascular prominence and adenopathy were specific (86%, 91% and 93%).

CONCLUSION

MRE compares favorably to colonoscopy for evaluation of known or suspected Crohn's disease noninvasively and without the exposure to ionizing radiation associated with CT enterography (CTE).

Contrast-enhanced ultrasonography (CEUS) vs. MRI of the small bowel in the evaluation of Crohn's disease activity

PURPOSE

The presence of disease activity in Crohn's disease (CD) is one of the main parameters used to establish whether optimal therapy should be drug therapy or surgery. However, a major problem in monitoring CD is the common mismatch between the patient's symptoms and imaging objective signs of disease activity. Bowel ultrasonography (US) has emerged as a low-cost, noninvasive technique in the diagnosis and follow-up of patients with CD. Accordingly, the use of contrast-enhanced US (CEUS) has made possible an evaluation of the vascular enhancement pattern, similar to the use of magnetic resonance imaging (MRI). The aim of our study was to evaluate the role of CEUS in comparison with small-bowel MRI for assessing Crohn's disease activity.

MATERIALS AND METHODS

We prospectively enrolled 30 consecutive patients with known CD. Clinical and laboratory data were compared with imaging findings obtained from MRI and CEUS of the small bowel. MRI was performed with a 1.5-T system using phased-array coils and biphasic orally administered contrast agent prior to and after gadolinium chelate administration. We performed US with a 7.5-MHz linear-array probe and a second-generation contrast agent. The parameters analysed in both techniques were the following: lesion length, wall thickness, layered wall appearance, comb sign, fibroadipose proliferation, presence of enlarged lymph nodes and stenosis. We classified parietal enhancement curves into two types in relation to the contrast pattern obtained with the time-intensity curves at MRI and CEUS: (1) quick washin, quick washout, (2) slow washin, plateau with a slow washout.

RESULTS

Comparison between Crohn's disease activity index (CDAI) and MRI showed a low correlation, with an rho=0.398; correlation between CDAI-laboratory data and CEUS activity was low, with rho=0.354; correlation between MRI activity and CEUS activity was good, with rho = 0.791; high correlation was found between CEUS and MRI of the small bowel when assessing wall-thickness, lymph nodes and comb sign; good correlation was fund when assessing layered wall appearance, disease extension and fibroadipose proliferation. At MRI, time-intensity curves for 12/30 patients were active, compared with for 14/30 patients at CEUS; therefore there was a poor correlation between curve on CEUS and curve on MRI (r=0.167; p=0.36).

CONCLUSIONS

The use of CEUS can be recommended if there is a discrepancy between MRI and clinical/laboratory parameters. MRI of the small bowel remains the most accurate method for evaluating disease activity.

Small bowel imaging in Crohn's disease

Imaging of Crohn's disease of the small bowel is gradually moving away from barium fluoroscopy and towards cross-sectional modalities. This review explores the strengths and limitations of various techniques, and focuses on several current questions in small bowel imaging, such as the comparison between oral ingestion or nasojejunal intubation and enteroclysis for introduction of contrast, the use of computerised tomography (CT) versus magnetic resonance (MR) and the likely changes over the next decade.

Ileal Crohn disease: mural microvascularity quantified with contrast-enhanced US correlates with disease activity

PURPOSE

To quantitatively assess microvascular activation in the thickened ileal walls of patients with Crohn disease (CD) by using contrast-enhanced ultrasonography (US) and evaluate its correlation with widely used indexes of CD activity.

MATERIALS AND METHODS

This prospective study was approved by the ethics committee, and written informed consent was obtained from all patients. The authors examined 54 consecutively enrolled patients (mean age, 35.29 years; age range, 18-69 years; 39 men, 15 women) with endoscopically confirmed CD of the terminal ileum. Ileal wall segments thicker than 3 mm were examined with low-mechanical-index contrast-enhanced US and a second-generation US contrast agent. The authors analyzed software-plotted time-enhancement intensity curves to determine the maximum peak intensity (MPI) and wash-in slope coefficient (β) and evaluated their correlation with (a) the composite index of CD activity (CICDA), (b) the CD activity index (CDAI), and (c) the simplified endoscopic score for CD (SES-CD, evaluated in 37 patients) for the terminal ileum. Statistical analysis was performed with the Mann-Whitney test, Spearman rank test, and receiver operating characteristic (ROC) analysis.

RESULTS

MPI and β coefficients were significantly increased in the 36 patients with a CICDA indicative of active disease (P<.0001 for both), the 33 patients with a CDAI of at least 150 (P<.032 and P<.0074, respectively), and the 26 patients with an SES-CD of at least 1 (P<.0001 and P<.002, respectively). ROC analysis revealed accurate identification (compared with CICDA) of active CD with an MPI threshold of 24 video intensity (VI) (sensitivity, 97%; specificity, 83%) and a β coefficient of 4.5 VI/sec (sensitivity, 86%; specificity, 83%).

CONCLUSION

Contrast-enhanced US of the ileal wall is a promising method for objective, reproducible assessment of disease activity in patients with ileal CD.

Gastroenterology review and perspective: the role of cross-sectional imaging in evaluating bowel damage in Crohn disease

OBJECTIVE

This article will review the performance and limitations of cross-sectional imaging methods to detect and display critical features of Crohn disease (CD)-related bowel damage, including stenosis and penetrating complications (i.e., fistula, abscess). International efforts to incorporate cross-sectional imaging findings along with endoscopic and surgical findings to create a global bowel damage score over the length of the gastrointestinal tract are summarized along with the rationale for these efforts.

CONCLUSION

The first digestive damage score, the Lémann score, will incorporate surgical history, endoscopic findings, and imaging findings of stenosis and penetrating complications to provide a global assessment of CD-related destruction of the gastrointestinal tract. It is anticipated that the score will permit better understanding of the impact of modern therapeutics on the natural history of CD. Because CT is a technique that involves ionizing radiation and accuracy of ultrasound is highly related to CD location, MRI is proposed as first choice for nonemergent follow-up of CD patients.

Prospective evaluation of MR enterography as the primary imaging modality for pediatric Crohn disease assessment

OBJECTIVE

The objectives of this study were prospective evaluation of MR enterographic accuracy for detecting Crohn disease imaging features in pediatric patients, compared with a CT reference standard, as well as determination of MR enterographic accuracy for detecting active bowel inflammation and fibrosis using a histologic reference standard.

SUBJECTS AND METHODS

The study group for this blinded prospective study included 21 pediatric subjects with known Crohn disease scheduled for clinical CT and histologic bowel sampling for symptomatic exacerbation. All subjects and their parents gave informed consent to also undergo MR enterography. CT and MR enterography examinations were independently reviewed by two radiologists and were scored for Crohn disease features. All bowel histology specimens were reviewed by a single pathologist for the presence of active mucosal inflammation and mural fibrosis, followed by correlation of imaging and histologic findings.

RESULTS

All 21 subjects underwent MR enterography and histologic sampling, 18 of whom also underwent CT. MR enterography had high sensitivity for detecting Crohn disease imaging features (e.g., bowel wall thickening, mesenteric inflammation, lymphadenopathy, fistula, and abscess) compared with CT, with individual sensitivity values ranging from 85.1% to 100%. Of a total of 53 abnormal bowel segments with correlation of MRI and histologic findings, MR enterography showed 86.7% accuracy (90.0% sensitivity and 82.6% specificity) for detecting active inflammation (p < 0.001). The accuracy of MR enterography for detecting mural fibrosis overall was 64.9%, compared with histology, but increased to 83.3% (p < 0.05) for detecting fibrosis without superimposed active inflammation.

CONCLUSION

MR enterography can substitute for CT as the first-line imaging modality in pediatric patients with Crohn disease, on the basis of its ability to detect intestinal pathologic abnormalities in both small and large bowel as well as extraintestinal disease manifestations. Additionally, MR enterography provides an accurate noninvasive assessment of Crohn disease activity and mural fibrosis and can aid in formulating treatment strategies for symptomatic patients and assessing therapy response.

Contrast-enhanced ultrasound (CEUS) in Crohn's disease: technique, image interpretation and clinical applications

BACKGROUND: Recent meta-analysis has demonstrated no significant differences in diagnostic accuracy among different imaging techniques (US, MRI and CT) in the evaluation of Crohn's disease (CD). High-resolution bowel ultrasound has emerged as an alternative imaging technique for the diagnosis and follow-up of patients with CD, being as accurate as CT and MR for detecting intramural and extramural extension of the disease. B-Mode US can evaluate the localization and length of the affected intestinal segments and allow identification of transmural complications, stenosis and intestinal obstruction. Doppler techniques are tools that visualize and quantify bowel vascularization. Contrast-enhanced ultrasound (CEUS) is a new technique that involves IV administration of an ultrasound contrast agent with real-time examination, providing an accurate depiction of the bowel wall microvascularization and the perienteric tissues. The introduction of imaging quantification techniques enables an objective quantitative measurement of the enhancement. METHOD AND RESULTS: The article reviews the technique, sonographic findings, advantages and limitations, and clinical applications of contrast-enhanced US in the evaluation of Cohn's disease. Current CEUS applications in CD are: CD activity assessment, evaluation of inflammatory masses, distinguishing phlegmons from abscesses, characterization of stenosis by differentiating fibrosis from inflammation, monitoring the efficacy of drug treatments and improving the detection of disease recurrence. CONCLUSION: CEUS is an emerging technique that is part of the entire sonographic evaluation, with a role in the diagnosis and follow-up of CD, thus improving therapy planning and monitoring of the efficacy of treatment. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s13244-011-0124-1) contains supplementary material, which is available to authorized users.

Active Crohn's disease in the small bowel: evaluation by diffusion weighted imaging and quantitative dynamic contrast enhanced MR imaging

PURPOSE

To determine relative diagnostic value of MR diffusion and perfusion parameters in detection of active small bowel inflammation in patients with Crohn's disease (CD).

MATERIALS AND METHODS

We reviewed 18 patients with active CD of terminal ileum (TI) who underwent MR enterography (MRE; including dynamic contrast enhanced MRI and diffusion-weighted MRI). Conventional MRI findings of TI were recorded. Regions of interest were drawn over TI and normal ileum to calculate apparent diffusion coefficient (ADC), the volume transfer constant (K(trans)) and the contrast media distribution volume (v(e)). Receiver operating characteristic analysis was used to determine their diagnostic performance.

RESULTS

Among conventional MR findings, mural thickening and increased enhancement were present in all actively inflamed small bowel. K(trans), v(e), and ADC values differed significantly between actively inflamed TI and normal ileum (0.92 s(-1) versus 0.36 s(-1); 0.31 versus 0.15 ± 0.08; 0.00198 mm(2)/s versus 0.00311 mm(2)/s; P < 0.001). Area under the curve (AUC) for K(trans), v(e), and ADC values ranged from 0.88 to 0.92 for detection of active inflammation. Combining K(trans) and ADC data provided an AUC value of 0.95.

CONCLUSION

Dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI) provide quantitative measures of small bowel inflammation that can differentiate actively inflamed small bowel segments from normal small bowel in CD. DWI provides better sensitivity compared with DCE-MRI and combination of ADC and K(trans) parameters for analysis can potentially improve specificity.

Role of Magnetic Resonance Enterography in Differentiating between Fibrotic and Active Inflammatory Small Bowel Stenosis in Patients with Crohn's Disease

Objective:

To assess the diagnostic accuracy of magnetic resonance imaging (MRI) in prospectively differentiating between fibrotic and active inflammatory small bowel stenosis in patients with Crohn's disease (CD).

Materials and Methods:

A total of 111 patients with histologically proven CD presenting with clinical and plain radiographic signs of small bowel obstruction underwent coronal and axial MRI scans after oral administration of polyethylene glycol solution. A stenosis was judged present if a small bowel segment had >80% lumen reduction as compared to an adjacent normal loop and mural thickening of >3 mm. At the level of the stenosis, both T2 signal intensity and post-gadolinium T1 enhancement were quantified using a 5-point scale (0: very low; 1: low; 2: moderate; 3: high; and 4: very high). A stenosis was considered fibrotic if the sum of the two values (activity score: AS) did not exceed 1.

Results:

A small bowel stenosis was identified in 48 out of 111 patients. Fibrosis was confirmed at histology in all of the 23 patients with AS of 0 or 1, who underwent surgery within 3 days of the MRI examination. In the remaining 25 patients (AS: 2–8), an active inflammatory stenosis was suspected and remission of the obstructive symptoms was obtained by means of medical treatment. One of these patients (AS: 2), however, underwent surgery after 14 days, due to recurrence. MRI had 95.8% sensitivity, 100% specificity, and 97.9% accuracy in the diagnosis of fibrotic stenosis.

Conclusion:

MRI is reliable in differentiating fibrotic from inflammatory small bowel stenosis in CD.

Interobserver and intermodality agreement for detection of small bowel Crohn's disease with MR enterography and CT enterography

BACKGROUND

Magnetic resonance enterography (MRE) and computed tomography enterography (CTE) visualizes small bowel Crohn's disease (CD) and its complications with high accuracy. The aim of this study was to determine the interobserver and intermodality agreement for detection of small bowel CD.

METHODS

Fifty patients with suspected or known CD were included in the study and all patients underwent MRE and CTE on the same day. Four radiologists with experience in MRE and CTE techniques participated. Observers were blind to patient histories, results of ileocolonoscopies, and other small bowel examinations. Readers assessed the image quality, the presence of small bowel CD, and seven findings consistent with CD.

RESULTS

The image quality was better with CTE than MRE (P < 0.001) but the diagnostic yields were comparable (P = 0.4). For detection of small bowel CD, the interobserver agreement was substantial in CTE (κ = 0.64) and moderate in MRE (κ = 0.48). The intermodality agreement was fair to substantial (κ = 0.40-0.64) for different observers. Two abscesses were detected and confirmed at subsequent surgery. One abscess was not detected with MRE and only recorded by two observers in CTE. A total of 10 fistulas were detected: three were confirmed at subsequent surgery and four were false-positive findings.

CONCLUSIONS

MRE and CTE have comparable diagnostic yields in patients with suspected or known CD. However, CTE provides better image quality and interobserver agreement. In a substantial number of patients the diagnosis of small bowel CD is observer- and modality-dependent.

Magnetic resonance enterocolonography is useful for simultaneous evaluation of small and large intestinal lesions in Crohn's disease

BACKGROUND

We developed novel magnetic resonance enterocolonography (MREC) for simultaneously evaluating both small and large bowel lesions in patients with Crohn's disease (CD). The aim of this study was to evaluate the diagnostic performance of MREC by comparing results of this procedure to those of endoscopies for evaluating the small and large bowel lesions of patients with CD.

METHODS

Thirty patients with established CD were prospectively examined by newly developed MREC. Patients underwent ileocolonoscopy (ICS) (24 procedures) or double-balloon endoscopy (DBE) (10 procedures) after MREC on the same day. Two gastroenterologists and two radiologists who were blinded to the results of another study evaluated endoscopy and MREC findings, respectively.

RESULTS

In colonic lesions the sensitivities of the MREC for deep mucosal lesions (DML), all CD lesions, and stenosis were 88.2, 61.8, and 71.4%, respectively, while the specificities were 98.1, 95.3, and 97.7%, respectively. In small intestinal lesions, MREC sensitivities for DML, all CD lesions, and stenosis were 100, 85.7, and 100%, respectively, while specificities were 100, 90.5, and 93.1%, respectively. Endoscopic scores were significantly correlated with MREC scores. Eleven (46%) of the 24 patients who were clinically not suspected to show stricture were observed to demonstrate stricture by radiologists.

CONCLUSIONS

Our results demonstrated that MREC can simultaneously detect the CD lesions of the small and large intestine. MREC can be performed without radiation exposure, the use of enema, or the placement of a naso-jejunal catheter. MREC and endoscopy have comparable abilities for evaluating mucosal lesions of patients with CD.

Guide to magnetic resonance in Crohn's disease: from common findings to the more rare complicances

Considering that multiple imaging examinations are often necessary for monitoring Crohn's disease (CD) activity and severity in order to guide and monitor appropriate treatment, the ideal imaging test would be reproducible, well tolerated by patients, and free of ionizing radiation. For these reasons recent studies have highlighted the role of a magnetic resonance imaging (MRI) technique optimized for small bowel imaging in the evaluation of small bowel disorders. In this regard there are two main methodological approaches represented by MR enterography, following administration of an oral contrast medium, and MR enteroclysis, following administration of contrast medium through a nasojejuneal tube. MRI may be used to demonstrate the pathologic findings and complications of CD. In particular, MR has excellent sensitivity and specificity, ranging from 88%-98% and 78%-100%, respectively, for the detection of active inflammation, wall thickening, ulcerations, increased wall enhancement, increased vascularity, perienteric inflammation, and reactive adenopathy. MR also allows more accurate identification of associated complications including penetrating and fibrostenotic disease as well as the more rare extraintestinal manifestations that are usually associated with severe and longstanding intestinal inflammation, the latter often guiding the therapeutic approach. In the progression of CD some rare complications can occur that, to our knowledge, were only briefly or never mentioned in the radiological literature regarding MR enterography or enteroclysis and in which the application of these techniques play a key role.

Which magnetic resonance imaging findings accurately evaluate inflammation in small bowel Crohn's disease? A retrospective comparison with surgical pathologic analysis

BACKGROUND

The aim was to evaluate the value of magnetic resonance imaging (MRI) findings in Crohn's disease (CD) in correlation with pathological inflammatory score using surgical pathology analysis as a reference method.

METHODS

CD patients who were to undergo bowel resection surgery underwent MR enterography before surgery. The CD pathological inflammatory score of the surgical specimens was classified into three grades: mild or nonactive CD, moderately active CD, and severely active CD; fibrosis was also classified into three grades: mild, moderate, and severe. Mural and extramural MRI findings were correlated with pathological inflammatory and fibrosis grades.

RESULTS

Fifty-three consecutive patients were included retrospectively. The mean delay between MRI and surgery was 24 days (range 1-90, median 14). The CD pathological inflammatory score was graded as follows: grade 0 (11 patients, 21%), grade 1 (15 patients, 28%), and grade 2 (27 patients, 51%). MRI findings significantly associated with pathological inflammatory grading were wall thickness (P < 0.0001), degree of wall enhancement on delayed phase (P < 0.0001), pattern of enhancement on both parenchymatous (P = 0.02), and delayed phase, (P = 0.008), T2 relative hypersignal wall (P < 0.0001), blurred wall enhancement (P = 0.018), comb sign (P = 0.004), fistula (P < 0.0001), and abscess (P = 0.049). The inflammation score correlated with the fibrosis score (r = 0.63, P = 0.0001).

CONCLUSIONS

Our study identified MRI findings significantly associated with surgical pathological inflammation. These lesions are considered potentially reversible and may be efficiently treated medically. We also showed that fibrosis was closely and positively related to inflammation.

MRI in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) affects ≈1.4 million people in North America and, because of its typical early age of onset and episodic disease course, IBD patients often undergo numerous imaging studies over the course of their lifetimes. Computed tomography (CT) has become the standard imaging modality for assessment of IBD patients because of its widespread availability, rapid image acquisition, and ability to evaluate intraluminal and extraluminal disease. However, repetitive CT imaging has been associated with a significant ionizing radiation risk to patients, making MRI an appealing alternative IBD imaging modality. Pelvic MRI is currently the imaging gold standard for detecting perianal disease, while recent studies indicate that MRI bowel-directed techniques (enteroclysis, enterography, colonography) can accurately evaluate bowel inflammation in IBD. With recent technical innovations leading to faster and higher resolution body MRI, the role of MRI in IBD evaluation is likely to continue to expand. Future applications include surveillance imaging, detection of mural fibrosis, and early assessment of therapy response.

Retrospective comparison of magnetic resonance imaging features and histopathology in Crohn's disease patients

PURPOSE

To retrospectively compare histopathological findings of surgically resected bowel segments with magnetic resonance imaging (MRI) findings on Crohn's disease activity.

MATERIALS AND METHODS

Patients who underwent a MR enterography or enteroclysis before surgery were included after informed consent. MRI features (T1-enhancement, T1 and T2 stratification, T2 signal intensity, bowel wall thickness, presence of ulcerations, comb sign, creeping fat, and disease activity) were assessed by three experienced abdominal radiologists. An acute inflammatory score based on histopathology (parameters: mucosal ulceration, edema, depth and degree of neutrophils) was calculated. Interobserver variability for subjective MRI features was also assessed.

RESULTS

Thirty-nine segments in 25 patients (mean age 38 years) were included. Of the MRI features, disease activity per segment and bowel wall thickness had a positive association with the acute inflammatory score (p<0.05). T1-enhancement had a positive correlation with disease chronicity. All other MRI features did not have an association with the acute inflammatory score. Interobserver agreement between the three observers was weak to moderate.

CONCLUSION

MR features bowel wall thickness and disease activity per-segment reflect disease activity in Crohn's disease patients.

Magnetic resonance enterography for suspected inflammatory bowel disease in a pediatric population

OBJECTIVES

The aim of the study was to determine the accuracy of magnetic resonance enterography (MRE) in diagnosing and differentiating pediatric inflammatory bowel disease (IBD). The secondary aims were to determine the accuracy of MRE in grading disease activity and determine the interobserver agreement for individual MRE parameters.

PATIENTS AND METHODS

Pediatric patients scheduled to undergo esophagogastroduodenoscopy, ileocolonoscopy with biopsies, and barium enteroclysis for suspected IBD were included and underwent MRE. MRE images were evaluated by 3 observers. The accuracy of MRE was calculated using the clinical diagnosis based on endoscopic, histopathological, and barium enteroclysis examinations as reference standard.

RESULTS

Thirty-three patients were available for analysis. IBD was correctly diagnosed in, respectively, 61%, 61%, and 91% of the patients by the 3 observers, with a specificity of 80%, 90%, and 60%. Differentiation between Crohn disease (CD) and ulcerative colitis (UC) was accurately done in, respectively, 67%, 53%, and 80% of patients with CD and 0%, 14%, and 43% of patients with UC. Disease activity was understaged on MRE in the majority of patients. Intraclass correlation coefficients for measurements of bowel thickness were 0.52 (observer 1-2; observer 1-3) and 0.34 (observer 2-3). Interobserver agreement on bowel wall enhancement and stenosis was moderate to good (κ 0.59, 0.56, and 0.56 and κ 0.62, 0.32, 0.30, respectively).

CONCLUSIONS

Sensitivity and specificity values of MRE for diagnosing pediatric IBD were moderate to good. CD, but not UC, was accurately diagnosed by MRE in a large proportion of patients. Activity was understaged in a large proportion of patients. Interobserver agreement for individual MRE parameters was fair to good.

MR enterography with polyethylene glycol as oral contrast medium in the follow-up of patients with Crohn disease: comparison with CT enterography

BACKGROUND

To compare magnetic resonance enterography (MRE) and computed tomography enterography (CTE) in detecting inflammatory bowel disease activity (IBD) in patients with Crohn's disease (CD).

METHODS

A total of 29 patients (M 20; F 9; mean age 43.8 ± 15.9) with known CD underwent MRE. MRE was performed at 1.5 T using phased-array sense body coil, after oral administration of 1.5-2 L of PEG solution as oral contrast agent. MRE protocol included T1-weighted, sSShT2, sBTFE and gadolinium-enhanced THRIVE sequences acquired on coronal and axial planes. CTE was performed using a 16 multidetector-row computed-tomography before and after intravenous administration of 120 mL of iodinated contrast. MRE images and CTE scans were reviewed by a radiologist for bowel thickness and enhancement, mesenteric lymph nodes, vascular engorgement, fibrofatty proliferation, fistulas and abscesses. The disease activity was also defined by CDAI > 150.

RESULTS

MRE has demonstrated a good sensitivity in detection of CD activity, particularly in depiction of mural thickening, mural enhancement, and vascular engorgement. The level of agreement between the two technique was excellent in evaluating wall thickening with mucosal hyperenhancement (κ = 1), comb (κ = 0.90) and halo signs (κ = 0.86). In detecting fibrofatty proliferation and mesenteric lymph nodes, CTE was superior to MRE (accuracy: P < 0.05), while MRE was superior in visualization of fistulas.

CONCLUSION

MRE is an accurate method in monitoring the activity of CD as compared to CTE and may be considered an alternative to CTE in assessing degree of CD and evaluating therapeutic effectiveness.

Derivation of a T2-weighted MRI total colonic inflammation score (TCIS) for assessment of patients with severe acute inflammatory colitis-a preliminary study

OBJECTIVE

To derive an MRI score for assessing severity, therapeutic response and prognosis in acute severe inflammatory colitis.

METHODS

Twenty-one patients with acute severe colitis underwent colonic MRI after admission and again (n = 16) after median 5 days of treatment. Using T2-weighted images, two radiologists in consensus graded segmental haustral loss, mesenteric and mural oedema, mural thickness, and small bowel and colonic dilatation producing a total colonic inflammatory score (TCIS, range 6-95). Pre- and post-treatment TCIS were compared, and correlated with CRP, stool frequency, and number of inpatient days (therapeutic response marker). Questionnaire assessment of patient worry, satisfaction and discomfort graded 1 (bad) to 7 (good) was administered

RESULTS

Admission TCIS correlated significantly with CRP (Kendall's tau=0.45, 95% confidence interval [CI] 0.11-0.79, p = 0.006), and stool frequency (Kendall's tau 0.39, 95% CI 0.14-0.64, p = 0.02). TCIS fell after treatment (median [22 range 15-31]) to median 20 [range 8-25], p = 0.01. Admission TCIS but not CRP or stool frequency was correlated with length of inpatient stay (Kendall's tau 0.40, 95% CI 0.11-0.69, p = 0.02). Patients reported some discomfort (median score 4) during MRI.

CONCLUSIONS

MRI TCIS falls after therapy, correlates with existing markers of disease severity, and in comparison may better predict therapeutic response.

Magnetic resonance follow-through imaging for evaluation of disease activity in ileal Crohn's disease: an observational, retrospective cohort study

BACKGROUND

Magnetic resonance follow-through (MRFT) is a new cross-sectional imaging modality with the potential to accurately stage ileal Crohn's disease (CD), while avoiding ionizing radiation and the discomfort associated with enteroclysis. We aimed to assess the reliability of this technique in assessing the extent and activity of ileal CD, and to assess its influence on subsequent management.

METHODS

Out of a total of 342 patients undergoing MRFT between 2004 and 2008, 221 were performed in 191 patients with confirmed CD. Case notes were reviewed in detail with documentation of all investigations pre- and post-MRFT. Agreement between inflammatory markers, histopathology, and MRFT findings was determined.

RESULTS

Overall, 116/221 (52.5%) of MRFTs showed active ileal CD, and 76/221 (34.4%) quiescent CD, while 29/221 (13.1%) were suboptimal. Overall, 66 strictures and 18 fistulae were identified. There was substantial agreement between active ileal CD on MRFT and histopathology (n = 59; kappa = 0.66; P = 0.0006; sensitivity 85.1%, specificity 85.7%) and fecal calprotectin (n = 14; kappa = 0.72; P = 0.047), while C-reactive protein (CRP) showed moderate agreement (n = 107; kappa = 0.402; P = 0.00028). Management was influenced by MRFT reports following active (52/84, 62% treated medically) or quiescent (48/62, 77.4% managed conservatively) disease. Fibrotic strictures were predominantly treated surgically (7/14, 50%). In all, 13/32 (40.6%) patients with inflammatory ileal strictures required surgery, mostly due to steroid-resistant disease. Overall, 75 MR findings were documented in 221 MRFTs, including 1 renal cancer.

CONCLUSIONS

MRFT provides accurate information on ileal CD activity, with close agreement to inflammatory markers and histopathology. It represents a substantial advance in the staging of CD, while avoiding painful enteroclysis and radiation exposure in young patients.

Benefits and challenges in bowel MR imaging at 3.0 T

Abdominal imaging at 3.0 T has shown to be challenging because of a number of artifacts and effects related to the physics at higher field strength. For bowel imaging at 3.0 T, artifacts due to magnetic field inhomogeneities, standing waves, increased susceptibility, and greater chemical shift effects are of particular concern because they are likely to affect the assessment of relevant structures and counterbalance the benefits of higher signal-to-noise ratio. Regarding small- and large-bowel magnetic resonance imaging, the benefits of higher field strengths translate mainly in better contrast-to-noise ratio of contrast-enhanced T1-weighted gradient echo and T2-weighted imaging, whereas steady-state free precession sequences seem to suffer from serious degradation of image quality. The present article summarizes the technical challenges in bowel imaging at 3.0 T, provides an overview of performance compared with 1.5 T in small- and large-bowel diseases including the rectum, and revises the current literature.

ACR Appropriateness Criteria on Crohn's disease

In the past decade, new therapeutic agents have been developed that permit gastroenterologists to treat virtually all forms of Crohn's disease. The success of these treatments depends on an accurate diagnosis of the nature and extent of disease. Fortunately, radiologists now possess a powerful arsenal of imaging techniques to guide the choice of therapy. This article discusses the usefulness of both traditional and newer imaging techniques in the management of Crohn's disease and its various clinical presentations.

Imaging of cell trafficking in Crohn's disease

Inflammatory bowel diseases are represented by ulcerative colitis and Crohn's disease, both consisting of a chronic, uncontrolled inflammation of the intestinal mucosa of any part of the gastrointestinal tract with patchy or continuous inflammation. Ileo-colonoscopy is considered the current gold standard imaging technique for the diagnosis. However, as the majority of patients need a long-term follow-up it would be ideal to rely on a non-invasive technique with good compliance. This review focuses on nuclear medicine imaging techniques in Crohn's disease. Different scintigraphic methods of imaging cells involved in the pathogenesis are described. The radiopharmaceuticals can be divided into non-specific radiopharmaceuticals for inflammation and specific radiopharmaceuticals that directly image lymphocytes involved in the process. This non-invasive molecular imaging approach can be useful also because it images the small bowel or other areas--where colonoscopy is not useful-and that it may play a role for constant follow-up, because relapses are frequent. Finally, an update on other imaging modalities, and particularly MRI, in the evaluation of Crohn's disease activity, is provided. Although MRI cannot directly detect inflammatory cells, it has shown a high sensitivity in detecting the macroscopic signs of inflammation at the level of the intestinal wall affected by Crohn's disease and Ulcerative colitis. The current diagnostic value of MRI in the detection of inflamed bowel segment and in the assessment of CD activity, as well the potentials MR spectroscopy, MR diffusion imaging and MR molecular imaging, is briefly discussed.

MR colonography and MR enterography

The bowel is a common site for pathologic processes, including malignancies and inflammatory disease. Colorectal cancer accounts for 10% of all new cancers and 9% of cancer deaths. A significant decrease in the incidence of colorectal cancer and cancer death rates has been attributed to screening measures, earlier detection, and improved therapies. Virtual colonoscopy (VC), also known as computed tomography colonography, is an effective method for detecting polyps. However, in light of increasing concerns about ionizing radiation exposure from medical imaging and potential increased risk of future radiation-induced malignancies, magnetic resonance imaging (MRI) is seen as an increasingly attractive alternative. Improvements in MRI technology now permit three-dimensional volumetric imaging of the entire colon in a single breath hold at high spatial resolution, making VC with MRI possible.

MR imaging of the small bowel

Cross-sectional imaging techniques are playing an increasing role in the evaluation of suspected small-bowel disorders, and a growing awareness of the risks of ionizing radiation exposure has prompted the exploration of alternative imaging techniques. Advantages of magnetic resonance (MR) imaging include a lack of ionizing radiation, the ability to provide dynamic information regarding bowel distention and motility, improved soft-tissue contrast, and a relatively safe intravenous contrast agent profile. Limitations of MR imaging include cost, imager access, variability in examination quality, and lower spatial and temporal resolution compared with those of computed tomography (CT). MR imaging of the small bowel is indicated for patients with Crohn disease, those for whom exposure to radiation is a concern, those with contraindications to CT, and those with low-grade small-bowel obstruction. MR imaging may be performed with enterography or enteroclysis. In enterography, large volumes of fluid are ingested. Several different contrast agents may be used. These agents are classified according to their signal intensity on T1- and T2-weighted images. In enteroclysis, enteric contrast material is administered through a nasoenteric tube. Crohn disease is the primary indication for MR imaging of the small bowel because many patients require multiple follow-up examinations. Findings suggestive of active inflammation include bowel wall thickening and hyperenhancement, ulcerations, increased mesenteric vascularity, and perienteric inflammation. Complications are well depicted and may include penetrating disease and small-bowel obstruction.

Endoscopy and MR enteroclysis: equivalent tools in predicting clinical recurrence in patients with Crohn's disease after ileocolic resection

BACKGROUND

Ileocolonoscopy poses the gold standard in the evaluation of postoperative recurrence of Crohn's disease (CD) at the site of ileocolonic anastomosis. Magnetic resonance enteroclysis (MRE) on the other hand is a promising technique for small bowel imaging. The aim was to compare MRE and ileocolonoscopy for predicting clinical recurrence in CD patients who have undergone ileocolonic resection.

METHODS

We included 29 patients in the study. The median time since index operation was 35 months and between ileocolonoscopy and MRE was 3 days. Patients were followed up for a maximum of 2 years unless clinical recurrence occurred earlier. Endoscopic findings were evaluated on a 5-grade scale (i0-i4), whereas MRE findings on the neoterminal ileum and anastomosis were assessed according to a previously validated 4-grade scale MR score (MR0-MR3).

RESULTS

By classifying patients into subgroups of endoscopic severity of postoperative recurrence using as a threshold an endoscopic score of i3, we found that 10% of patients in the i0 to i2 group had a clinical recurrence during the 2-year follow-up period as compared to 52.6% of subjects with i3 to i4 (P = 0.043). The corresponding clinical exacerbation rates in the subgroups based on MRE severity assessment were 12.5% for MR0 to MR1 and 50% for MR2 to MR3 (P = 0.09).

CONCLUSIONS

Our data suggest that colonoscopy and MR enteroclysis are of similar value to predict the risk of clinical recurrence in postoperative patients with Crohn's disease.

Quantitative analysis of dynamic contrast enhanced MRI for assessment of bowel inflammation in Crohn's disease pilot study

RATIONALE AND OBJECTIVES

The aim of this study was to evaluate the feasibility of quantitative analysis of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) data in the detection of bowel inflammation in patients with Crohn's disease.

MATERIALS AND METHODS

Eleven patients who underwent magnetic resonance enterography for known or suspected Crohn's disease and had colonoscopy or surgery within 4 weeks of imaging were included in this study. DCE-MRI data were acquired using a 1.5-T scanner with temporal resolution of 5 to 12 seconds for approximately 5 to 7 minutes. A two-compartment pharmacokinetic model was used to analyze the data to obtain the volume transfer constant (K(trans)) and the extravascular extracellular space (v(e)). Additionally, semiquantitative parameters were derived using an empirical mathematical model to fit the contrast concentration curves. Endoscopic, surgical, and pathologic results were compared to the MRI data. Receiver-operating characteristic analysis was performed to compare the diagnostic accuracy of the parameters in the task of distinguishing normal tissue from inflammation.

RESULTS

A total of 51 bowel segments (19 with inflammation, 32 normal) were included in the analyses. Inflamed bowel segments had faster K(trans) values, larger v(e) values, increased contrast uptake, larger initial areas under the contrast concentration curve, and steeper initial enhancement slopes than normal bowel segments (P < .05). The areas under the receiver-operating characteristic curve for these parameters ranged from 0.70 to 0.86.

CONCLUSION

These preliminary results demonstrate that the quantitative analysis of DCE-MRI data is possible for the assessment of bowel inflammation in patients with Crohn's disease. Future studies need be performed on larger numbers of patients to correlate the severity and type of inflammation with kinetic parameters.

Magnetic resonance imaging detects intestinal barrier dysfunction in a rat model of acute mesenteric ischemia/reperfusion injury

OBJECTIVES

To develop an in vivo intestinal permeability assay applying magnetic resonance imaging (MRI) to monitor real-time gut barrier defects in animal models of acute mesenteric ischemia/reperfusion (I/R) insult.

MATERIALS AND METHODS

Twenty Wistar rats were divided to 2 groups for I/R challenge or sham controls. I/R rats received occlusion of superior mesenteric artery for 20 minutes and reperfusion for 1 hour. Sham-operation controls received laparotomy without manipulation of artery. To assess gut permeability, a 10-cm jejunal sac was created distal to the ligament of Treitz in both groups of rats after laparotomy, and a contrast agent (gadodiamide) was injected into the lumen of the ligated intestinal sac. The signals produced by gadodamide in the liver, kidney, and plasma before and after the start of reperfusion were examined by 1.5 Tesla MRI (GE Signa Excite), and the increment of signal-to-noise ratio (SNR) in these organs that parallels the luminal-to-serosal flux rate of the probe was used as an indicator of gut permeability. At the end of procedures, jejunal tissues and mucosal scrapings were collected for histologic examination and Western blotting for epithelial tight junctional proteins. Moreover, liver and spleen homogenates were cultured on fresh blood agar plates to measure the bacterial colony-forming units per gram of tissue.

RESULTS

In I/R rats, disrupted villous structure and decreased epithelial tight junctional expression were seen in the jejunum associated with massive enteric bacterial translocation to the liver and spleen. The SNR in the liver of I/R rats was higher than sham controls (2.65 +/- 0.56 vs. 0.65 +/- 0.26, P < 0.01) at 15 minutes postreperfusion. Elevation of SNR in the kidney was also found in I/R rats compared with sham controls (11.61 +/- 2.07 vs. 3.06 +/- 1.15, P < 0.05). The plasma gadodiamide concentration in I/R rats was significantly increased compared with sham controls (0.220 +/- 0.044 vs. 0.006 +/- 0.004 mM, P < 0.01) at 15 minutes postreperfusion.

CONCLUSIONS

This novel MRI-based intestinal permeability assay has shown a significant increase in the signal intensity in liver, kidney, and plasma samples that correlated with mucosal barrier defects in experimental models of acute mesenteric I/R.