MRI diffusion-weighted imaging (DWI) in pediatric small bowel Crohn disease: correlation with MRI findings of active bowel wall inflammation

MRI and Blood-based Biomarkers Are Associated With Surgery in Children and Adults With Ileal Crohn's Disease

BACKGROUND

Despite advances in medical therapy, many children and adults with ileal Crohn's disease (CD) progress to fibrostenosis requiring surgery. We aimed to identify MRI and circulating biomarkers associated with the need for surgical management.

METHODS

This prospective, multicenter study included pediatric and adult CD cases undergoing ileal resection and CD controls receiving medical therapy. Noncontrast research MRI examinations measured bowel wall 3-dimensional magnetization transfer ratio normalized to skeletal muscle (normalized 3D MTR), modified Look-Locker inversion recovery (MOLLI) T1 relaxation, intravoxel incoherent motion (IVIM) diffusion-weighted imaging metrics, and the simplified magnetic resonance index of activity (sMaRIA). Circulating biomarkers were measured on the same day as the research MRI and included CD64, extracellular matrix protein 1 (ECM1), and granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies (Ab). Associations between MRI and circulating biomarkers and need for ileal resection were tested using univariate and multivariable LASSO regression.

RESULTS

Our study sample included 50 patients with CD undergoing ileal resection and 83 patients with CD receiving medical therapy; mean participant age was 23.9 ± 13.1 years. Disease duration and treatment exposures did not vary between the groups. Univariate biomarker associations with ileal resection included log GM-CSF Ab (odds ratio [OR], 2.87; P = .0009), normalized 3D MTR (OR, 1.05; P = .002), log MOLLI T1 (OR, 0.01; P = .02), log IVIM perfusion fraction (f; OR, 0.38; P = .04), and IVIM apparent diffusion coefficient (ADC; OR, 0.3; P = .001). The multivariable model for surgery based upon corrected Akaike information criterion included age (OR, 1.03; P = .29), BMI (OR, 0.91; P = .09), log GM-CSF Ab (OR, 3.37; P = .01), normalized 3D MTR (OR, 1.07; P = .007), sMaRIA (OR, 1.14; P = .61), luminal narrowing (OR, 10.19; P = .003), log C-reactive protein (normalized; OR, 2.75; P = .10), and hematocrit (OR, 0.90; P = .13).

CONCLUSION

After accounting for clinical and MRI measures of severity, normalized 3D MTR and GM-CSF Ab are associated with the need for surgery in ileal CD.

Isolated Terminal Ileitis in Children

Isolated terminal ileitis in adults is a well described entity that rarely progresses to Crohn disease (CD), and pediatric literature on this topic is very limited. We describe the prevalence, clinical, endoscopic, histologic, and radiological features, along with long-term outcome of isolated terminal ileitis in our institution. We reviewed charts of 956 children who underwent colonoscopy from 2013 to 2017. Thirty-three children had isolated histologically-defined terminal ileitis. Seventeen children were diagnosed with CD and 16 children had idiopathic terminal ileitis. Children with CD had higher prevalence of abnormal C-reactive protein levels, severe inflammation, and radiological evidence of bowel wall thickening compared with children with idiopathic ileitis. Children with idiopathic ileitis did not develop CD over a follow-up period of 83 months. In contrast to adults, CD is common in children with isolated terminal ileitis and those with idiopathic ileitis do well over long-term.

Apparent diffusion coefficient for assessing Crohn's disease activity: a meta-analysis

PURPOSE

To analyze relationships betweenapparent diffusion coefficient (ADC) and activity parameters of Crohn's disease, e.g., length and wall thickness, CRP, FCP, MaRIA, CDAI, SES-CD, histologic inflammatory activity score, and the histological fibrotic score, based upon published data.

MATERIALS AND METHODS

MEDLINE library, Scopus, and Embase databases were screened for association between ADC and activity parameters of Crohn's disease in patients with Crohn's disease up to Mai 2021. Overall, 21 studies with 1053 patients were identified. The following data were extracted from the literature: number of patients, correlation coefficients between ADC and length as well as wall thickness, CRP, FCP, MaRIA, CDAI, and SES-CD, inflammatory activity score, and fibrotic score. Associations between ADC and activity parameters were analyzed by Spearman's correlation coefficient. The studies' methodologic quality was evaluated by using the Quality Assessment of Diagnostic Studies (QUADAS 2) instrument, revealing a low risk of bias.

RESULTS

In the overall sample, the pooled correlation coefficient between ADC and CDAI was -0.8 (95% CI = [-0.94; -0.65]), between ADC and MaRIA -0.66 (95% CI = [-0.79; -0.53]). A strong association was observed between ADC and SES-CD with a pooled correlation of -0.66 (95% CI = [-0.87; -0.46]). The pooled sensitivity to discriminate between involved and non-involved bowel segments was 0.89, with an area under the curve of 0.89 CONCLUSIONS: ADC showed strong inverse correlations with CDAI, MaRIA, and SES-CD scores. However, the role of ADC in assessing fibrotic changes in the bowel wall is limited. ADC can reflect acute inflammatory reactions but not systemic inflammation.

KEY POINTS

• ADC value can reflect acute inflammatory reactions but not systemic inflammation. • ADC is inversely correlated with CDAI, MaRIA, and SES-CD. • The role of ADC in assessing fibrotic changes in the bowel wall is limited.

DWI ratios: New indexes for Crohn's disease activity at magnetic resonance enterography?

BACKGROUND

The aim of the study was to provide radiologists and clinicians a rapid tool for assessment of intestinal inflammation in Crohn's disease (CD) patients through quantification of diffusion-weighted imaging (DWI) signal intensity while performing magnetic resonance enterography (MRE).

MATERIALS AND METHODS

A monocentric retrospective study was conducted between September 2018 and July 2021 on CD patients who underwent MRE. Two radiologists measured signal intensity on DWI scans at the highest b-value (800 s/mm²) within pathologic intestinal walls, lymph nodes, spleen and psoas muscle and calculated the relative ratios. Spearman, Mann-Whitney and Jonckheere-Terpstra tests were applied for estimating correlation among ratios, significant differences between the two patient groups and determining the trend in relation to endoscopic classes. Wilcoxon's and Cronbach's alpha tests were employed for comparison of DWI measurements and ratios between the two observers.

RESULTS

Fifty-nine patients were enrolled in the study. In the non-surgical group, correlation has been found among Simple Endoscopic Score for Crohn's Disease (SES-CD) classes and the different ratios: bowel/spleen (p = 0.034), bowel/psoas (p = 0.008) and bowel/lymph node (p = 0.010). Within the surgical group, positive correlation was found only between bowel/lymph node ratio and bowel/psoas ratio (p = 0.014). The J-T test demonstrated an increasing monotonic trend for bowel/psoas ratio and bowel/lymph node ratio and SES-CD classes. Inter-reader evaluation demonstrated no statistical differences for DWI measurements and high degree of concordance for the final ratios.

CONCLUSION

DWI ratios correlate with endoscopic classes in non-surgical patients and have inter-observer reproducibility.

Quantitative abdominal magnetic resonance imaging in children-special considerations

The use of quantitative MRI methods for assessment of the abdomen in children has become commonplace over the past decade. Increasingly employed methods include MR elastography, chemical shift encoded (CSE) MR imaging for determination of proton density fat fraction, diffusion-weighted imaging, and a variety of relaxometry techniques, such as T1 and T2* mapping. These techniques can be used in a variety of settings to distinguish normal from abnormal tissue as well as determine the severity of disease. The performance of quantitative MRI methods in the pediatric population presents unique challenges as compared to adult populations. These challenges relate to multiple factors, including patient size, pediatric physiology, inability to breath hold, and greater physical motion during the examination. The purpose of this review article is to review quantitative MRI methods that may be used in clinical practice to assess the pediatric abdomen and to discuss special considerations when performing these techniques in children.

Clinical, radiological, and magnetic resonance imaging characteristics of axial spondyloarthritis with late onset

We aimed to investigate the clinical, diagnostic, and imaging features of patients with late onset axial spondyloarthritis (SpA) with initial symptom manifestation aged over 45 years. Participants with axial SpA were consecutively recruited. Clinical, demographic, blood, and imaging parameters were compared between the groups with early (≤45 years) and late onset (>45 years) at a cross-sectional level. Logistic regressions were used to determine the independent associations with axial SpA with late onset. A total of 455 participants were recruited. Among them, 70 (15.4%) had late onset disease. Multivariate analyses showed that axial SpA with late onset was associated with higher C-reactive protein based ankylosing spondylitis disease activity index (ASDAS-CRP) (B = 0.10; P = .04), higher intensity of spinal inflammation as measured by maximum apparent diffusion coefficient (spinal ADC max) (B = 0.27; P = .03) and mean ADC (spinal ADC mean) (B = 0.30; P = .004), lower modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) (B = -0.12; P = .02), more tender joint count (B = 0.12; P = .02), and fewer inflammatory back pain (IBP) (OR = 0.26; P < .001). Axial SpA with late onset had higher clinical disease activity, higher intensity of spinal MRI inflammation, less radiographic damage, and more tender joint count. There was also less inflammatory back pain, which could make the diagnosis more difficult.

Role of Cross-Sectional Imaging in Pediatric Inflammatory Bowel Disease

BACKGROUND

The association between radiological remission and natural history of disease in children with inflammatory bowel diseases (IBD) is poorly known.

AIMS

(i) To assess the correlation between cross-sectional imaging (CSI) (ultrasound and magnetic resonance imaging) and clinical, biomarker and endoscopic disease activity; (ii) to evaluate the impact of radiological activity on the occurrence of complications in pediatric patients with IBD.

METHODS

A retrospective study including pediatric patients with IBD and radiological follow-up of at least one year was conducted between 2003 and 2019 at the Nancy University Hospital.

RESULTS

In total, 118 patients (66 Crohn's disease (CD) and 52 ulcerative colitis (UC)) were included. Median follow-up duration was 5.2 years (range: 1.1-15.4). Seventeen (25.8%) patients with CD and 7 (13.5%) patients with UC achieved and maintained radiological remission until last follow-up. No IBD patient achieving radiological remission experienced complications or relapse. In patients not achieving radiologic remission, complications and surgery occurred in 13/49 (26.5%) and 8/49 (16.3%) patients with CD and in 5/45 (11.1%) and 5 (11.1%) subjects with UC. Among patients with CD, the association for remission status between radiological and endoscopic assessment was excellent (Cramer's V test (V) = 0.50), and moderate between radiological and either clinical (V = 0.30) or biochemical (V = 0.33) assessments. In UC, the association for remission status between radiological and either endoscopic or clinical assessments were weak (V = 0.19 and V = 0.20 respectively), and moderate (V = 0.23) between radiological and biochemical assessments.

CONCLUSION

CSI may replace endoscopic monitoring in pediatric CD. Radiological remission status predicts long-term disease outcomes.

Diagnostic Performance of Diffusion-weighted Imaging for Evaluation of Bowel Inflammation in Paediatric Inflammatory Bowel Disease: A Systematic Review and Meta-analysis

BACKGROUND AND AIMS

The diagnostic performance of diffusion-weighted imaging magnetic resonance enterography [DWI-MRE] has not been clearly established in a paediatric population. We systematically evaluated the diagnostic performance of DWI-MRE for the detection of bowel inflammation in paediatric patients with suspected or known inflammatory bowel disease [IBD].

METHODS

MEDLINE/PubMed, EMBASE, Web of science and the Cochrane library were searched for articles investigating the diagnostic performance of DWI-MRE for the detection of bowel inflammation in paediatric patients with suspected or known IBD up to December 31, 2020. Pooled sensitivity and specificity were calculated using a bivariate random-effects model. Pooled inter-reader agreement for the interpretation of DWI-MRE was also calculated. This study was registered as PROSPERO CRD42021228754.

RESULTS

Nine studies covering 400 paediatric patients were included. The pooled sensitivity and specificity of DWI-MRE for the detection of bowel inflammation were 0.93 (95% confidence interval [CI], 0.88-0.96) and 0.96 [95% CI, 0.87-0.99], respectively. Substantial heterogeneity was noted in both sensitivity [I2 = 66%; p < 0.01] and specificity [I2 = 94%; p < 0.01]. Meta-regression analysis identified that the use of spasmolytics contributed to higher specificity [0.89-0.99] and that quantitative assessment with an apparent diffusion coefficient cut-off value contributed to lower sensitivity [0.93-0.85] and specificity [0.98-0.72]. The pooled coefficient of inter-reader agreement, including four studies using visual assessment, was 0.97 [95% CI, 0.78-1.00].

CONCLUSIONS

DWI-MRE, especially when used with spasmolytics, is accurate for the detection of bowel inflammation in paediatric patients with suspected or known IBD. Quantitative measurement of ADC is not practical for this purpose.

Both ASDAS and ADC are associated with spinal mobility in active axial spondyloarthritis: A comparison between early and later disease

OBJECTIVE

Using diffusion-weighted imaging (DWI)-derived apparent diffusion coefficient (ADC), we aimed to determine the relationship between intensity of spinal inflammation and mobility in patients with axial spondyloarthritis (SpA) in early and later stages of active disease. The Ankylosing Spondylitis Disease Activity Score (ASDAS) was also used for a more comprehensive evaluation.

METHODS

Participants with axial SpA and back pain were recruited from 10 rheumatology centers. Clinical, biochemical and radiological parameters were collected. Short tau inversion recovery (STIR) sequence magnetic resonance imaging (MRI) and DWI of the spine and sacroiliac (SI) joints were performed. ADC maps were generated. Participants were examined for Bath Ankylosing Spondylitis Metrology Index (BASMI). Linear regression models were used to determine associations between BASMI and various clinical, radiological, and MRI parameters in participants with active inflammation on spinal ADC maps.

RESULTS

One-hundred and twenty-seven participants were included in the analyses. Multivariate linear regression showed that mean ADC spine (ß = .16; P = .03), ASDAS-C-reactive protein (CRP) (ß = .29, P < .001), and ASDAS-erythrocyte sedimentation rate (ESR) (ß = .25, P < .01) were associated with BASMI. In participants with duration of back pain ≤3 years, mean spine ADC (ß = .37; P = .03), ASDAS-CRP (ß = .44; P = .01), and ASDAS-ESR (ß = .42; P = .01) were associated with BASMI after adjustment for confounding factors. In participants with duration of back pain >3 years, only ASDAS-CRP (ß = .25; P < .01) and ASDAS-ESR (ß = .20; P = .20) were associated with BASMI.

CONCLUSION

Intensity of inflammation and clinical disease activity were independently associated with impairment of spinal mobility. The associations were stronger in early (≤3 years) than later disease.

Usefulness of Colon Assessment by Magnetic Resonance Enterography in Pediatric Patients with Inflammatory Bowel Disease-Retrospective Case Series

Background: Magnetic resonance enterography (MRE) is an excellent way to study the small bowels. During such an examination, the colon is also seen within the field of study. The aim of this study was to evaluate the effectiveness of MRE in detecting characteristics of active inflammatory bowel disease (IBD) in the colon, in comparison to different features seen in colonoscopies. Methods: This retrospective study was conducted with 41 children. Features of active inflammation we considered were wall thickening; contrast enhancement; incorrect signal in the DWI sequence in the MRE; and presence of ulceration, erosion, erythema, spontaneous bleeding and a decrease of the vascular pattern seen in colonoscopy. The colon was divided into six segments: caecum, ascending, transverse, descending, sigmoid and rectum. Results: The sensitivity of MRE was, on average, 50–75%, and as high as 92–100%, depending on the segment. The most important feature for which there was the most dependencies was ulceration. In the analysis of intestinal wall thickness, the AUC value >0.8 was detected as ulceration (segments: cecum, ascending, descending colon, sigmoid), spontaneous bleeding (ascending colon and sigmoid) and decreased vascular pattern (ascending, transverse, descending colon). Conclusions: Evaluation of qualitative structural changes in MRE distinguishes patients with inflammation in colonoscopy from patients without lesions, with high diagnostic accuracy, albeit higher specificity than sensitivity.

Diagnostic performance of magnetic resonance enterography and ultrasound in children with inflammatory bowel diseases: a diagnostic test accuracy meta-analysis

OBJECTIVES

Magnetic resonance enterography (MRE) and ultrasound (US) can be used to diagnose inflammatory bowel diseases (IBD) in children. This meta-analysis aimed to determine the diagnostic performance of MRE and US in pediatric patients with IBD.

METHODS

PubMed, Embase, and the Cochrane Library were searched for eligible studies published up to June 1, 2020. The outcomes were the performances of MRE and US at the segment and patient levels. Pooled sensitivity, specificity, positive and negative likelihood ratios (PLR and NLR), diagnostic odds ratio (DOR), and the area under the summary receiver operating characteristic curves value (SROC) were analyzed.

RESULTS

Eight studies (340 children) were included. Compared with the reference standard, MRE showed pooled sensitivity of 93.0% (95% confidence interval (CI): 90.0-95.4%), specificity of 94.6% (95% CI: 92.1-96.5%), PLR of 11.146 (95% CI: 5.027-24.713), NLR of 0.094 (95% CI: 0.057-0.155), and DOR of 134.21 (95% CI: 40.72-442.29), with a SROC of 0.9721. Similar results were observed at the patient and segment levels. Compared with the reference standard, US had pooled sensitivity of 84.1% (95% CI: 69.9-93.4%), specificity of 82.9% (95% CI: 66.4-93.4%), PLR of 4.924 (95% CI: 2.351-10.310), NLR of 0.207 (95% CI: 0.103-0.413), and DOR of 25.919 (95% CI: 7.63-88.07), but only two studies were included. US (reader 1) had a similar diagnostic value to US (reader 2).

CONCLUSIONS

The present meta-analysis shows that MRE has good performance in detecting IBD in pediatric patients. Only two studies used US, and additional studies are necessary to confirm the diagnostic performance of US for IBD in children.

KEY POINTS

• MRE has good performance in the detection of IBD in pediatric patients. • Similar results were observed at the patient and segment levels for MRE. • Only two studies were included for US, without differentiating patient/segment.

Multi-shot Diffusion-Weighted MRI With Multiplexed Sensitivity Encoding (MUSE) in the Assessment of Active Inflammation in Crohn's Disease

BACKGROUND

Single-shot diffusion-weighted imaging (ssDWI) has been shown useful for detecting active bowel inflammation in Crohn's disease (CD) without MRI contrast. However, ssDWI suffers from geometric distortion and low spatial resolution.

PURPOSE

To compare conventional ssDWI with higher-resolution ssDWI (HR-ssDWI) and multi-shot DWI based on multiplexed sensitivity encoding (MUSE-DWI) for evaluating bowel inflammation in CD, using contrast-enhanced MR imaging (CE-MRI) as the reference standard.

STUDY TYPE

Prospective.

SUBJECTS

Eighty nine patients with histological diagnosis of CD from previous endoscopy (55 male/34 female, age: 17-69 years). FIELD STRENGTH/SEQUENCES: ssDWI (2.7 mm × 2.7 mm), HR-ssDWI (1.8 mm × 1.8 mm), MUSE-DWI (1.8 mm × 1.8 mm) based on echo-planar imaging, T2-weighted imaging, and CE-MRI sequences, all at 1.5 T.

ASSESSMENT

Five raters independently evaluated the tissue texture conspicuity, geometry accuracy, minimization of artifacts, diagnostic confidence, and overall image quality using 5-point Likert scales. The diagnostic performance (sensitivity, specificity and accuracy) of each DWI sequences was assessed on per-bowel-segment basis.

STATISTICAL TESTS

Inter-rater agreement for qualitative evaluation of each parameter was measured by the intra-class correlation coefficient (ICC). Paired Wilcoxon signed-rank tests were performed to evaluate the statistical significance of differences in qualitative scoring between DWI sequences. A P value <0.05 was considered to be statistically significant.

RESULTS

Tissue texture conspicuity, geometric distortions, and overall image quality were significantly better for MUSE-DWI than for ssDWI and HR-ssDWI with good agreement among five raters (ICC: 0.70-0.89). HR-ssDWI showed significantly poorer performance to ssDWI and MUSE-DWI for all qualitative scores and had the worst diagnostic performance (sensitivity of 57.0% and accuracy of 87.3%, with 36 undiagnosable cases due to severe artifacts). MUSE-DWI showed significantly higher sensitivity (97.5% vs. 86.1%) and accuracy (98.9% vs. 95.1%) than ssDWI for detecting bowel inflammation.

DATA CONCLUSION

MUSE-DWI was advantageous in assessing bowel inflammation in CD, resulting in improved spatial resolution and image quality.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 2.

Paediatric gastrointestinal and hepatobiliary radiology: why do we need subspecialists, and what is new?

We present the case for subspecialisation in paediatric gastrointestinal and hepato-pancreatico-biliary radiology. We frame the discussion around a number of questions: What is different about the paediatric patient and paediatric gastrointestinal system? What does the radiologist need to do differently? And finally, what can be translated from these subspecialty areas into everyday practice? We cover conditions that the sub-specialist might encounter, focusing on entities such as inflammatory bowel disease and hepatic vascular anomalies. We also highlight novel imaging techniques that are a focus of research in the subspecialties, including contrast-enhanced ultrasound, MRI motility, magnetisation transfer factor, and magnetic resonance elastography.

Clinical-stage Approaches for Imaging Chronic Inflammation and Fibrosis in Crohn's Disease

The number of imaging-based indices developed for inflammatory bowel disease as research tools, objectively measuring ileocolonic and perianal activity and treatment response, has expanded in the past 2 decades. Created primarily to assess Crohn's disease (CD), there is increasing adoption of these indices into the clinical realm to guide patient care. This translation has been facilitated by validation in adult and pediatric populations, prompted by simplification of score calculations needed for practical application outside the research environment. The majority of these indices utilize magnetic resonance imaging (MRI), specifically MR enterography (MRE) and pelvic MRI, and more recently ultrasound. This review explores validated indices by modality, anatomic site and indication, including for documentation of the presence and extent of CD, disease progression, complications, and treatment response, highlighting those in clinical use or with the potential to be. As well, it details index imaging features used to quantify chronic inflammatory activity, severity, and to lesser extent fibrosis, in addition to their reference standards and any modifications. Validation in the pediatric population of indices primarily developed in adult cohorts such as the Magnetic Resonance Index of Activity (MaRIA), the Simplified Magnetic Resonance Index of Activity (MARIAs), and the MRE global score (MEGS), together with newly developed pediatric-specific indices, are discussed. Indices that may be predictive of disease course and investigational techniques with the potential to provide future imaging biomarkers, such as multiparametric MRI, are also briefly considered.

Intensity of spinal inflammation is associated with radiological structural damage in patients with active axial spondyloarthritis

Objective

The aim was to investigate the relationship between the intensity of spinal inflammation using the apparent diffusion coefficient (ADC) and radiographic progression in axial SpA.

Methods

This is a cross-sectional study of participants with axial SpA and back pain. Clinical, biochemical and radiological parameters were collected. The ankylosing spondylitis disease activity score (ASDAS)-CRP was determined. Radiographic progression was represented by the modified Stoke ankylosing spondylitis spine score (mSASSS). MRI with short tau inversion recovery (STIR) and diffusion-weighted imaging sequences were performed simultaneously. Inflammatory lesions on STIR were used for the Spondyloarthritis Research Consortium of Canada (SPARCC) MRI indexes and as references in outlining regions of interest in ADC maps to produce mean (ADC_mean) and maximal (ADC_max) ADC values. Univariate and multivariate linear regression analyses were used to determine independent associations between ADC and radiographic progression.

Results

The 84 participants with identifiable lesions on spinal ADC maps recruited were characterized by a mean (s.d.) age of 45.01 (13.68) years, long disease duration [13.40 (11.01) years] and moderate clinical disease activity [ASDAS-CRP 2.07 (0.83)]. Multivariate regression analysis using ADC_mean as the independent variable showed that age (regression coefficient [B] = 0.34; P = 0.01), male sex (B = 0.25; P = 0.04) and ADC_mean (B = 0.30; P = 0.01) were positively associated with mSASSS. Multivariate regression analysis using ADC_max as the independent variable showed a tendency for ADC_max to be associated with mSASSS (B = 0.21; P = 0.07).

Conclusion

The intensity of spinal inflammation as determined by ADC is associated with radiographic progression in participants with active axial SpA.

Magnetic resonance enterography

Crohn's disease is a condition of chronic inflammation that may involve any part of the gastrointestinal tract, although it more frequently affects the terminal ileum. Longstanding inflammation may lead to several bowel complications including obstruction, stricture, fistula and abscesses which often necessitate surgery. Cross-sectional imaging methods such as computed tomography and magnetic resonance imaging are being utilized more frequently to assess mural and extramural inflammatory bowel disease manifestations. Magnetic resonance enterography (MRE) for assessment of small bowel is optimal because of absence of ionizing radiation, better soft tissue contrast, development of motion-free sequences and high resolution images. A typical protocol includes pre and postcontrast sequences utilizing an enteric contrast agent for adequate bowel distention and an antiperistaltic agent. Overall, MRE allows the evaluation of disease activity, extraenteric complication and response to therapy with a great impact on patient management. In this review we discuss the features of MRE from patient's preparation and exam protocol to pathological findings.

ASDAS is associated with both the extent and intensity of DW-MRI spinal inflammation in active axial spondyloarthritis

Objective

To investigate the relationship between Ankylosing Spondylitis Disease Activity Score (ASDAS) and intensity of spinal inflammation measured by apparent diffusion coefficient (ADC) in MRI in participants with active axial spondyloarthritis (SpA).

Methods

Participants with axial SpA and back pain were recruited. Clinical, demographic, biochemical and imaging data were collected. ASDAS was calculated based on C reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Inflammatory lesions were identified in short tau inversion recovery images and the corresponding ADC maps to determine the maximum apparent diffusion coefficient (ADCmax), normalised maximum ADC, mean apparent diffusion coefficient (ADCmean) and normalised mean ADC by two independent readers. Spondyloarthritis Research Consortium of Canada (SPARCC) spine and sacroiliac (SI) joint MRI indexes were determined. Univariate and multivariate linear regression models were used to determine the associations between of ASDAS with ADC values, SPARCC spine and SI MRI scores.

Results

Eighty-two participants had identifiable ADC lesions. Multivariate analyses using ADCmax and SPARCC spine MRI as independent variables showed associations with ASDAS-CRP (ADCmax: B=0.27, p=0.02; SPARCC: B=0.32, p=0.01) and ASDAS-ESR (ADCmax: B=0.24, p=0.03; SPARCC: B=0.36, p<0.01); using ADCmean and SPARCC spine MRI as independent variables also showed an association with ASDAS-ESR (ADCmean: B=0.22, p=0.05; SPARCC: B=0.36, p<0.01) and a tendency to associate with ASDAS-CRP (ADCmean: B=0.21, p=0.07; SPARCC: B=0.34, p<0.01).

Conclusion

ASDAS is associated with both the extent and the intensity of spinal inflammation in patients with detectable inflammatory lesions. Our results showed that ASDAS is an objective disease assessment tool.

Trial registration number

HKUCTR-2087.

Quantitative Analysis of Apparent Diffusion Coefficient for Disease Assessment in Paediatric Inflammatory Bowel Disease

OBJECTIVE

The aim of the study was to establish an apparent diffusion coefficient (ADC) cut-off value to classify active and non-active lesions in inflammatory bowel disease.

METHODS

We reviewed 167 paediatric magnetic resonance enterographies executed for suspected inflammatory bowel disease by using a 1.5- and 3-T scanner. We assessed the presence and activity of the disease by using morphologic and functional parameters such as the ADC. Each patient could have more than 1 examinations. Quantitative assessment of disease activity in the ADC map was measured placing 3 regions of interest in the areas of highest inflammation and the mean value was calculated, patients without sign of inflammation were assessed at 2 standardised site. Ileocolonoscopy, esophagogastroduodenoscopy, surgery, and video-capsule endoscopy were used as standards of reference.

RESULTS

We enrolled 34 patients and 35 examinations: radiological findings of disease were identified in 29 examinations and 44 lesions were detected. Six patients had negative results and ADC assessment was taken at the terminal ileum and cecum. A total of 56 bowel segments were included in the study. Image analysis revealed 39 active lesions (69.6%) and their ADC values were lower compared to the ones of non-active segments. For each scanner a cut-off value was found (sensitivity: 0.91, specificity: 0.89 for 1.5 T and 0.81 for 3 T). Inter-rater agreement on disease activity between ADC values and magnetic resonance enterography results and between ADC values and the standard of reference were very good.

CONCLUSIONS

ADC can provide a scanner-based quantitative measurement of disease activity.

Diffusion-weighted magnetic resonance enterography for prediction of response to tumor necrosis factor inhibitors in stricturing Crohn's disease

BACKGROUND AND AIMS

Distinguishing between fibrotic and inflammatory strictures in Crohn's disease (CD) is still challenging. The capacity of diffusion-weighted (DWI) magnetic resonance (MRE) to identify intestinal fibrosis was recently demonstrated; however, the therapeutic implications of this association have never been evaluated. The aim of the current study was to identify imaging features, including DWI, which can predict response to anti-inflammatory treatment in patients with stricturing CD.

METHODS

Consecutive CD patients with intestinal strictures that initiated treatment with anti-tumor necrosis alpha (anti-TNF) between June 2012 and April 2017 with MRE adjacent to treatment onset were retrospectively collected. The primary outcome was treatment failure, defined as drug discontinuation, CD-related surgery, or endoscopic dilatation of the stricture. Clinical, demographic, and imaging data were compared between patients who did and did not develop treatment failure within 12 months of anti-TNF treatment initiation.

RESULTS

A total of 21 patients were included in the study; 9/21 (42.8%) developed treatment failure. None of the clinical/demographic parameters were associated with the risk of treatment failure. Among imaging parameters, only ADC value (< 1 × 10^-3 mm²/s) was significantly associated with the risk of treatment failure (AUC = 0.81, 66% vs. 0%, p = 0.015).

CONCLUSIONS

Our results suggest that ADC value on DWI MRE may predict the risk of treatment failure in stricturing CD. If replicated in larger studies, these results may guide therapeutic decisions and suggest avoiding anti-TNF treatment.

Assessment of normal jejunum with diffusion-weighted imaging on MRE in children

BACKGROUND

Diffusion restriction has been utilized as a marker for bowel inflammation on magnetic resonance enterography (MRE). However, diffusion restriction has been seen in otherwise normal appearing small bowel in patients without active inflammation, with little published data on this subject.

OBJECTIVE

Assess diffusion restriction in normal loops of jejunum and to determine if there is a correlation to luminal distention, age, magnet field strength, slice thickness, and bowel segment location.

MATERIALS AND METHODS

A retrospective analysis of subjects with a normal MRE and clinical work-up was performed. The abdomen was divided into four quadrants. If available, two loops of jejunum were randomly chosen in each quadrant. Two radiologists evaluated the loops of jejunum for distension, wall thickness, enhancement and diffusion restriction. Disagreement was resolved by consensus. Presence of diffusion restriction was correlated with luminal distension, age, magnet field strength, slice thickness and abdominal quadrant.

RESULTS

One hundred ninety-seven loops of jejunum were evaluated in 39 subjects. Fifteen subjects (38.5%) had jejunal loops with diffusion restriction for a total of 28 loops. There was no correlation between diffusion restriction and luminal distension, age, magnet field strength or quadrant location (P>0.05, Pearson chi-squared test or Student's t-tests). Of the 15 subjects with a loop demonstrating diffusion restriction, additional loops with diffusion restriction were found in 40%. There was a very weak trend observed for greater slice thickness in patients with jejunal diffusion restriction (Student's t-test, P=0.10).

CONCLUSION

Jejunal diffusion restriction is a common finding in children with no clinical evidence of bowel pathology, irrespective of patient age, luminal distension, location of bowel loop and magnetic field strength. Further studies may be valuable in assessing the impact of slice thickness on subjective diffusion restriction in the jejunum.

Diagnostic Value of Diffusion-Weighted Imaging and Apparent Diffusion Coefficient in Assessment of the Activity of Crohn Disease: 1.5 or 3 T

Objective

The objective of this study is to evaluate the role of diffusion-weighted imaging (DWI) in assessment of the activity of Crohn disease (CD) and to explore differences between DWI in 3 T and 1.5 T.

Methods

Postcontrast magnetic resonance enterography with DWI of 72 patients with pathological proof of CD was retrospectively evaluated for restricted diffusion qualitatively and quantitavely in 3 T (n = 40) and 1.5 T (n = 32). Magnetic resonance activity score of 7 or higher was used as reference of activity.

Results

Fifty-five patients had active lesions. Diffusion-weighted imaging hyperintensity showed sensitivity (100%, 100%) and specificity (88.89%, 100%) in 1.5/3 T for activity assessment. Mean ± SD apparent diffusion coefficient for active lesions was 1.21 ± 0.42 and 1.28 ± 0.59 × 10⁻³ mm²/s in 1.5 and 3 T, respectively. The proposed cutoff values of 1.35 and 1.38 × 10⁻³ mm²/s in 1.5 and 3 T, respectively, had sensitivity (80%, 93%), specificity (100%, 90%), accuracy (88%, 93%), and no significant difference in accuracy between 1.5/3 T (P = 0.48).

Conclusions

Diffusion-weighted imaging hypersensitivity and apparent diffusion coefficient values accurately assessed the activity of CD. No significant statistical difference in diagnostic accuracy was detected between 1.5 and 3 T.

Diagnostic Performance of Magnetic Resonance Enterography for Detection of Active Inflammation in Children and Adolescents With Inflammatory Bowel Disease: A Systematic Review and Diagnostic Meta-analysis

Importance

Magnetic resonance (MR) enterography has the advantage over other techniques of being noninvasive, lacking ionizing radiation, and demonstrating excellent soft-tissue contrast to evaluate pediatric patients with inflammatory bowel disease (IBD).

Objective

To evaluate the diagnostic performance of MR enterography for detection of active inflammation in children and adolescents with known or suspected IBD.

Data Sources

A search of MEDLINE and EMBASE up to January 2, 2017, was performed to identify studies. Search terms included child, pediatric, adolescent, Crohn disease, inflammatory bowel disease, and magnetic resonance enterography. The search was limited to English-language publications.

Study Selection

Studies evaluating the diagnostic performance of MR enterography for detection of active inflammation in pediatric patients with known or suspected IBD were selected. Two reviewers independently assessed the eligibility of the selected articles.

Data Extraction and Synthesis

The study was performed and reported in accordance with the PRISMA guidelines. Pooled summary estimates of sensitivity and specificity were calculated using hierarchical logistic regression modeling.

Main Outcomes and Measures

The diagnostic performance of MR enterography for detection of active inflammation in pediatric patients with known or suspected IBD was the primary outcome. Subgroup analyses and meta-regression were performed.

Results

Eighteen original articles involving a total of 687 patients were included. The summary sensitivity was 83% (95% CI, 75%-89%), the summary specificity was 93% (95% CI, 90%-95%), and the area under the hierarchical summary receiver operating characteristic curve was 0.95 (95% CI, 0.93-0.97). The Higgins I2 statistics demonstrated substantial heterogeneity in terms of sensitivity (I2 = 84.1%) and specificity (I2 = 68.8%). Based on per-patient analysis, the summary sensitivity was 86% (95% CI, 78%-91%) and specificity was 91% (95% CI, 82%-96%). In meta-regression, among the various potential covariates, scanner manufacturer was associated with study heterogeneity.

Conclusions and Relevance

Magnetic resonance enterography, which is a noninvasive, radiation-free modality, demonstrates high diagnostic performance in the diagnosis of active inflammation in pediatric patients with IBD, especially at the per-patient level.

Assessment of patency capsule retention using MR diffusion-weighted imaging

OBJECTIVES

Evaluate the ability of MR diffusion-weighted imaging (DWI) to predict patency capsule retention in Crohn's disease (CD).

METHODS

Clinical and imaging data were prospectively reviewed for 80 CD patients following patency capsule administration and MR-DWI under institutional review board (IRB) approval with informed consent. Two radiologists separately assessed the presence/absence of restricted diffusion in the distal ileum. Apparent diffusion coefficients (ADC) from three regions of interest on the ileal wall were averaged. The association between restricted diffusion and retention, and sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated. Ability of ADC to predict retention was assessed with receiver operating characteristic (ROC) curve analysis.

RESULTS

Restricted diffusion in the distal ileum was associated with capsule retention (p = 0.001, p < 0.0001). Sensitivity, specificity, PPV and NPV of restricted diffusion for capsule retention were 100.0%, 46.2%, 30.0%, 100% and 100.0%, 56.9%, 34.9%, 100%, respectively, for two radiologists. Accuracy of ADC to predict retention was high (area under the curve = 0.851, p < 0.0001). An ADC of 1.47 mm²/s showed 90.0% sensitivity and 50.0% specificity for retention.

CONCLUSIONS

Sensitivity and NPV of restricted diffusion for patency capsule retention were 100%, suggesting that DWI may predict gastrointestinal tract capability to pass video camera endoscopy.

KEY POINTS

• Capsule endoscopy enables assessment of the gastrointestinal mucosa in Crohn's disease • Prior patency capsule administration is recommended to evaluate gastrointestinal tract patency • MR diffusion-weighted imaging may detect pathological constriction of the ileum • Restricted diffusion in the distal ileum was associated with capsule retention • MR-DWI may predict gastrointestinal tract capability to pass capsule endoscopy.

Rapid non-contrast magnetic resonance imaging for post appendectomy intra-abdominal abscess in children

BACKGROUND

Acute appendicitis, especially if perforated at presentation, is often complicated by postoperative abscess formation. The detection of a postoperative abscess relies primarily on imaging. This has traditionally been done with contrast-enhanced computed tomography. Non-contrast magnetic resonance imaging (MRI) has the potential to accurately detect intra-abdominal abscesses, especially with the use of diffusion-weighted imaging (DWI).

OBJECTIVE

To evaluate our single-center experience with a rapid non-contrast MRI protocol evaluating post-appendectomy abscesses in children with persistent postsurgical symptoms.

MATERIALS AND METHODS

In this retrospective, institutional review board-approved study, all patients underwent a clinically indicated non-contrast 1.5- or 3-Tesla abdomen/pelvis MRI consisting of single-shot fast spin echo, inversion recovery and DWI sequences. All MRI studies were reviewed by two blinded pediatric radiologists to identify the presence of a drainable fluid collection. Each fluid collection was further characterized as accessible or not accessible for percutaneous or transrectal drainage. Imaging findings were compared to clinical outcome.

RESULTS

Seven of the 15 patients had a clinically significant fluid collection, and 5 of these patients were treated with percutaneous drain placement or exploratory laparotomy. The other patients had a phlegmon or a clinically insignificant fluid collection and were discharged home within 48 h.

CONCLUSION

Rapid non-contrast MRI utilizing fluid-sensitive and DWI sequences can be used to identify drainable fluid collections in post-appendectomy patients. This protocol can be used to triage patients between conservative management vs. abscess drainage without oral/intravenous contrast or exposure to ionizing radiation.

Diffusion-weighted imaging in quiescent Crohn's disease: correlation with inflammatory biomarkers and video capsule endoscopy

AIM

To investigate the role of restricted diffusion in quiescent Crohn's disease (CD) patients and its association with inflammatory biomarkers and endoscopic disease.

MATERIAL AND METHODS

Fifty-two quiescent CD patients prospectively underwent magnetic resonance enterography (MRE) and video capsule endoscopy (VCE) and were tested for the inflammatory biomarkers, faecal calprotectin (FCP) and C-reactive protein (CRP). Restricted diffusion in the distal ileum was qualitatively (absence/presence) and quantitatively (apparent diffusion coefficient [ADC]) assessed by two readers. The VCE-based Lewis score was calculated for the distal ileum. Restricted diffusion sensitivity and specificity for VCE ulcerations were assessed for patients with elevated (>100 μg/g) or normal (<100 μg/g) FCP. Receiver operating characteristic (ROC) curve was used to assess the ability of ADC to identify patients with concurrent VCE ulceration and elevated FCP.

RESULTS

The sensitivity and specificity of restricted diffusion for patients with VCE ulceration were higher in patients with elevated FCP (reader 1: 71.4%, 80%, reader 2: 76.2%, 100%, respectively) compared to patients with normal FCP (reader 1: 46.2%, 61.5%; reader 2: 15.4%, 76.9%, respectively). The ADC had a high diagnostic accuracy for identifying patients that had concurrent VCE ulceration and elevated FCP (reader 1: AUC=0.819, reader 2: AUC=0.832).

CONCLUSION

In quiescent CD patients, the presence of restricted diffusion is suggestive of an active inflammation, associated with elevated FCP. Thus, DWI may serve as a clinical tool in the follow-up of these patients, implying subclinical inflammatory flares.

Advanced imaging techniques in pediatric body MRI

While there are many challenges specific to pediatric abdomino-pelvic MRI, many recent advances are addressing these challenges. It is therefore essential for radiologists to be familiar with the latest advances in MR imaging. Laudable efforts have also recently been implemented in many centers to improve the overall experience of pediatric patients, including the use of dedicated radiology child life specialists, MRI video goggles, and improved MR suite environments. These efforts have allowed a larger number of children to be scanned while awake, with fewer studies being done under sedation or anesthesia; this has resulted in additional challenges from patient motion and difficulties with breath-holding and tolerating longer scan times. In this review, we highlight common challenges faced in imaging the pediatric abdomen and pelvis and discuss the application of the newest techniques to address these challenges. Additionally, we highlight the newest advances in quantified imaging techniques, specifically in MR liver iron quantification. The techniques described in this review are all commercially available and can be readily implemented.

Quantification of inflammatory activity in patients with Crohn's disease using diffusion weighted imaging (DWI) in MR enteroclysis and MR enterography

Background Individual studies have demonstrated the potential of diffusion-weighted magnetic resonance imaging (DWI-MRI) for identifying inflamed bowel segments. However, these studies were conducted with rather small patient cohorts and in most cases by means of MR enterography only. Purpose To demonstrate the feasibility of detecting inflamed bowel segments in a large collective of patients with Crohn's disease using DWI in MR enteroclysis and MR enterography and to compare the results of both techniques, also considering clinical parameters by means of the Harvey-Bradshaw Index (HBI). Material and Methods Ninety-six patients underwent MRI enteroclysis and 35 patients MR enterography, both with additional DWI. The HBI as well as apparent diffusion coefficients (ADC) in areas of inflamed and normal bowel wall were determined. Thus resulting in 208 bowel segments that were visualized and subsequently statistically analyzed. Results There were no significant differences in ADC values in MR enteroclysis and MR enterography ( P = 0.383 in inflammation, P = 0.223 in normal wall). Areas of inflammation showed statistically highly significant lower ADC values than areas of normal bowel wall ( P < 0.001). An ADC threshold of 1.56 × 10^-3mm²/s can distinguish between normal and inflamed bowel segments with a sensitivity of 97.4% and a specificity of 99.2%. A highly significant correlation could be shown between ADC and HBI values ( P = 0.001). Conclusion DWI-MRI facilitates recognition of inflamed bowel segments in patients with Crohn's disease and the ADC values show an excellent correlation to the HBI. There were no significant differences in ADC values in MR enteroclysis and MR enterography. An ADC threshold of 1.56 × 10^-3mm²/s differentiates between normal and inflamed bowel wall.

Diffusion-weighted MRI Enables to Accurately Grade Inflammatory Activity in Patients of Ileocolonic Crohn's Disease: Results from an Observational Study

BACKGROUND

Diffusion-weighted imaging (DWI) is a novel technique to evaluate bowel inflammation in Crohn's disease (CD). It remains unclear whether DWI could differentiate grades of inflammation activity and add to the accuracy of conventional magnetic resonance enterography (MRE) in defining disease activity. We aimed to assess the accuracy of DWI for evaluating ileocolonic CD inflammation compared with conventional MRE, using ileocolonoscopy as reference standard.

METHODS

This was an observational study of CD patients who underwent both ileocolonoscopy and MRE with DWI. The conventional MRE and DWI findings of the ileocolon were scored from 0 to 3. The respective segment endoscopic disease activity was scored by simplified endoscopic score for Crohn's disease (SES-CD) and was graded as inactive (0-2), mild (3-6) or moderate-severe (≥7).

RESULTS

One hundred eighty-five bowel segments from 43 consecutive CD patients were evaluated and included inactive (n = 86), mild (n = 72), and moderate-severe (n = 27) ileo-colonic segments. The area under the receiver operating characteristics curve (AUC) of 0.973 for apparent diffusion coefficient (ADC) to differentiate active from inactive CD was significantly higher than those of conventional MRE parameters (AUC between 0.840 and 0.940). Higher accuracy of ADC (AUC = 0.919) for differentiating inactive-mild from moderate-severe CD was also shown compared with that of conventional MRE parameters (AUC between 0.868 and 0.915). ADC values demonstrated strongest correlation with SES-CD (r = -0.880) comparing to DWI SI and conventional MRE parameters (r between 0.787 and 0.867).

CONCLUSIONS

DWI enables to accurately grade inflammatory activity in patients of ileocolonic CD and may be better suited than conventional MRE for monitoring the activity of CD.

Diffusion-Weighted MR Enterography to Monitor Bowel Inflammation after Medical Therapy in Crohn's Disease: A Prospective Longitudinal Study

Objective

To prospectively evaluate the performance of diffusion-weighted imaging (DWI) to monitor bowel inflammation after medical therapy for Crohn's disease (CD).

Materials and Methods

Before and following 1–2 years of medical therapy, between October 2012 and May 2015, 18 randomly selected adult CD patients (male:female, 13:5; mean age ± SD, 25.8 ± 7.9 years at the time of enrollment) prospectively underwent MR enterography (MRE) including DWI (b = 900 s/mm²) and ileocolonoscopy. Thirty-seven prospectively defined index lesions (one contiguous endoscopy-confirmed inflamed area chosen from each inflamed anatomical bowel segment; 1–4 index lesions per patient; median, 2 lesions) were assessed on pre- and post-treatment MRE and endoscopy. Visual assessment of treatment responses on DWI in 4 categories including complete remission and reduced, unchanged or increased inflammation, and measurements of changes in apparent diffusion coefficient (ΔADC), i.e., pre-treatment–post-treatment, were performed by 2 independent readers. Endoscopic findings and CD MRI activity index (CDMI) obtained using conventional MRE served as reference standards.

Results

ΔADC significantly differed between improved (i.e., complete remission and reduced inflammation) and unimproved (i.e., unchanged or increased inflammation) lesions: mean ± SD (× 10^-3 mm²/s) of -0.65 ± 0.58 vs. 0.06 ± 0.15 for reader 1 (p = 0.022) and -0.68 ± 0.56 vs. 0.10 ± 0.26 for reader 2 (p = 0.025). DWI accuracy for diagnosing complete remission or improved inflammation ranged from 76% (28/37) to 84% (31/37). A significant negative correlation was noted between ΔADC and ΔCDMI for both readers with correlation coefficients of -0.438 and -0.461, respectively (p < 0.05).

Conclusion

DWI is potentially a feasible tool to monitor quantitatively and qualitatively bowel inflammation of CD after medical treatment.

Ultrasound and MRI predictors of surgical bowel resection in pediatric Crohn disease

BACKGROUND

Imaging predictors for surgery in children with Crohn disease are lacking.

OBJECTIVE

To identify imaging features of the terminal ileum on short-interval bowel ultrasound (US) and MR enterography (MRE) in children with Crohn disease requiring surgical bowel resection and those managed by medical therapy alone.

MATERIALS AND METHODS

This retrospective study evaluated patients 18 years and younger with Crohn disease undergoing short-interval bowel US and MRE (within 2 months of one another), as well as subsequent ileocecectomy or endoscopy within 3 months of imaging. Appearance of the terminal ileum on both modalities was compared between surgical patients and those managed with medical therapy, with the following parameters assessed: bowel wall thickness, mural stratification, vascularity, fibrofatty proliferation, abscess, fistula and stricture on bowel US; bowel wall thickness, T2 ratio, enhancement pattern, mesenteric edema, fibrofatty proliferation, abscess, fistula and stricture on MRE. A two-sided t-test was used to compare means, a Mann-Whitney U analysis was used for non-parametric parameter scores, and a chi-square or two-sided Fisher exact test compared categorical variables. Imaging findings in surgical patients were correlated with location-matched histopathological scores of inflammation and fibrosis using a scoring system adapted from the Simple Endoscopic Score for Crohn Disease, and a Spearman rank correlation coefficient was used to compare inflammation and fibrosis on histopathology.

RESULTS

Twenty-two surgical patients (mean age: 16.5 years; male/female: 13/9) and 20 nonsurgical patients (mean age: 14.8; M/F: 8/12) were included in the final analysis. On US, the surgical group demonstrated significantly increased mean bowel wall thickness (6.1 mm vs. 4.7 mm for the nonsurgical group; P = 0.01), loss of mural stratification (odds ratio [OR] = 6.3; 95% confidence interval [CI]: 1.4-28.4; P = 0.02) and increased fibrofatty proliferation (P = 0.04). On MRE, the surgical group showed increased mean bowel wall thickness (9.1 mm vs. 7.2 mm for the nonsurgical group; P = 0.02), increased mean T2 ratio (4.6 vs. 3.6 for the nonsurgical group; P = 0.03), different enhancement patterns (P = 0.03), increased mesenteric edema (P = 0.001) and increased stricture formation (OR = 8.2; 95% CI: 1.8-36.4; P = 0.005). Nineteen of 22 ileocecectomy specimens showed severe inflammation and 21/22 showed severe fibrosis, with significant correlation between inflammation and fibrosis scores (ρ = 0.55; P = 0.008); however, correlation with imaging findings was limited by the uniformity of findings on histopathology.

CONCLUSION

Children with terminal ileal Crohn disease requiring surgical bowel resection demonstrate more severe manifestations of imaging features traditionally associated with both active inflammation and chronic fibrosis than those managed medically on US and MRE, findings that are corroborated by histopathology. These features may potentially serve as imaging biomarkers indicating the necessity for surgical intervention.

CAIPIRINHA-accelerated T1w 3D-FLASH for small-bowel MR imaging in pediatric patients with Crohn's disease: assessment of image quality and diagnostic performance

BACKGROUND

The "Controlled Aliasing In Parallel Imaging Results In Higher Acceleration" (CAPIRINHA) technique greatly accelerates T1w 3D fast low angle shot (FLASH) scans while maintaining high image quality. We studied image quality and conspicuity of inflammatory lesions on CAIPIRINHA-accelerated imaging for pediatric small-bowel magnetic resonance imaging (MRI).

METHODS

Forty-four consecutive patients (mean 14±3 years, 18 girls) underwent small-bowel MRI (MR enterography, MRE) at 1.5 T including diffusion-weighted imaging (DWI), contrast-enhanced CAIPIRINHA 3D-FLASH and standard 2D-FLASH imaging. Crohn's disease (CD) was confirmed in 26 patients, 18 patients served as control. Independent blinded readings were performed for grading of image quality and conspicuity of CD lesions on CAIPIRINHA FLASH and standard FLASH images in comparison to a reference standard comprising imaging and endoscopic data.

RESULTS

CAIPIRINHA FLASH yielded significantly higher image quality with good inter-observer agreement (κ=0.68) and showed better visual delineation in 40% of the assessed bowel lesions, as compared to standard FLASH. There was full agreement for identification of CD patients between CAIPIRINHA and standard FLASH. CAIPIRINHA FLASH detected two small-bowel lesions that were not seen on standard FLASH. DWI revealed additional inflammatory lesions inconspicuous on contrast-enhanced imaging. MRE showed an overall diagnostic accuracy of 93%.

CONCLUSION

We present first evidence that CAIPIRINHA greatly accelerates T1w imaging in paediatric MRE without trade-off in image quality or lesion conspicuity and is thus preferable to standard FLASH imaging.

DWI in Pediatric Small-Bowel Crohn Disease: Are Apparent Diffusion Coefficients Surrogates for Disease Activity in Patients Receiving Infliximab Therapy?

OBJECTIVE

The purpose of this study was to determine prospectively whether bowel wall apparent diffusion coefficient (ADC) measurements can be used to monitor treatment response to infliximab therapy in the setting of pediatric small-bowel Crohn disease.

SUBJECTS AND METHODS

Twenty-eight pediatric subjects with newly diagnosed biopsy-proven Crohn disease of the distal or terminal ileum treated with infliximab were enrolled. Subjects underwent MR enterography at baseline, 1 month after therapy, and 6 months after therapy. Imaging features were documented, including bowel wall ADC and arterial or enteric phase contrast-enhanced signal intensity normalized to that of unenhanced imaging. A linear mixed model assessed the relationship between ADC and time; patient age and sex and azathioprine combination therapy were covariates. The diagnostic performance (with 95% CIs) of an increase in bowel wall ADC of 20% or more for identifying response to infliximab was calculated using a decrease in normalized contrast-enhanced bowel wall signal intensity of 20% or more as the reference standard.

RESULTS

Bowel wall ADC increased over time (mean [± SD], 1180 ± 200 × 10^-6 mm²/s at baseline, 1420 ± 420 × 10^-6 mm²/s at 1 month, and 1450 ± 450 × 10^-6 mm²/s at 6 months; p = 0.0003); azathioprine therapy modulated this rate of change (p = 0.003). There was a statistically significant negative correlation between change in ADC and change in normalized contrast-enhanced signal intensity over time (ρ = -0.36; p < 0.001). The diagnostic performance of change in ADC for identifying response to infliximab therapy was sensitivity of 0.58 (95% CI, 0.34-0.80), specificity of 0.52 (95% CI, 0.31-0.72), positive predictive value of 0.48 (95% CI, 0.27-0.69), and negative predictive value of 0.62 (95% CI, 0.38-0.82).

CONCLUSION

Bowel wall ADC increases over time in pediatric subjects receiving infliximab, but the diagnostic performance of ADC is likely insufficient for reliable treatment monitoring.

Detection of bowel inflammation with fused DWI/T2 images versus contrast-enhanced images in pediatric MR enterography with histopathologic correlation

PURPOSE

To evaluate the fused, colorized diffusion weighted imaging (DWI) and anatomic T2 images compared to routine contrast-enhanced T1 images at pediatric magnetic resonance enterography (MRE).

METHODS

Fused, colorized DWI/T2 images were created from patients with magnetic resonance enterography (MRE) and colonoscopy/biopsy. Radiologists noted inflammation in five bowel segments (terminal ileum-rectosigmoid colon) on postcontrast images and DWI/T2 images. Test characteristics and agreement were calculated.

RESULTS

For 20 patients, sensitivity/specificity/positive predictive value (PPV)/negative predictive value (NPV) were 0.53/0.90/0.77/0.76 for DWI/T2 and 0.45/0.90/0.72/0.73 for postcontrast images. Intraobserver agreement was ҡ=0.45-0.73. Interobserver agreement was ҡ=0.53 for DWI/T2 and ҡ=0.63 for postcontrast images.

CONCLUSION

DWI/T2 images are similar in sensitivity/specificity to contrast-enhanced images and with moderate intra/interobserver reliability.

MR enterography: how to deliver added value

MR enterography (MRE) is increasingly vital to the diagnosis and follow-up of children with Crohn disease. This diagnostic test, which can provide valuable information regarding the presence of intestinal inflammation, intestinal and intra-abdominal complications, and extra-intestinal disease-related manifestations, has the potential to directly impact both medical and surgical decision-making. Consequently, it is imperative that the interpretation and reporting of these examinations provide as much clinical information as possible. This article reviews specific ways radiologists can provide added value when interpreting MRE examinations in the setting of pediatric Crohn disease by (1) establishing the true extent of disease involvement, (2) subjectively and objectively assessing response to medical treatment and (3) accurately characterizing disease-related complications.

Diffusion-weighted imaging in pediatric body magnetic resonance imaging

Diffusion-weighted MRI is being increasingly used in pediatric body imaging. Its role is still emerging. It is used for detection of tumors and abscesses, differentiation of benign and malignant tumors, and detection of inflamed bowel segments in inflammatory bowel disease in children. It holds great promise in the assessment of therapy response in body tumors, with apparent diffusion coefficient (ADC) value as a potential biomarker. Significant overlap of ADC values of benign and malignant processes and less reproducibility of ADC measurements are hampering its widespread use in clinical practice. With standardization of the technique, diffusion-weighted imaging (DWI) is likely to be used more frequently in clinical practice. We discuss the principles and technique of DWI, selection of b value, qualitative and quantitative assessment, and current status of DWI in evaluation of disease processes in the pediatric body.

Pediatric inflammatory bowel disease: imaging issues with targeted solutions

To date, there have been many advances in inflammatory bowel disease (IBD) imaging in every cross-sectional imaging modality, particularly in children. The main emphasis in pediatric IBD imaging is on robust and reproducible measures of small bowel Crohn's disease inflammation, accurate diagnosis of IBD-related complications, and minimizing radiation burden to the patient, as repeat imaging is necessary over the course of their disease. In this article, we discuss the current state-of-the-art imaging techniques, in addition to routine fluoroscopy, including MR and CT enterography and bowel ultrasound. We also present the emerging use of new methods to characterize disease severity and distinguish active inflammation from fibrosis such as diffusion-weighted imaging, bowel elastography, and contrast-enhanced ultrasound. The diagnostic performance of particular examinations, their strengths and weaknesses, and role in IBD management will be discussed. Although these advanced imaging techniques applied to children are similar to those performed in adults, special considerations related to their application in pediatric patients will also be reviewed.

Quantitative apparent diffusion coefficient (ADC) values as an imaging biomarker for fibrosis in pediatric Crohn's disease: preliminary experience

PURPOSE

To compare histopathology with ADC values in strictured bowel segments in pediatric patients with known Crohn's disease and surgical bowel resection.

METHODS

Magnetic resonance enterography (MRE) images of 14 subjects with Crohn's disease who had surgical bowel resection for strictures were retrospectively reviewed. Five of 14 subjects had DWI (b=0, 500, 1000) sequences included in the MRE study. ADC measurements were made by placing ROI's in the strictured bowel wall and compared to full-thickness histologic analysis of resected specimens. ADC values were also compared to control ADC measurements (in normal and inflamed-nonstenotic bowel segments) as well as the mean ADC values of Crohn's patients published in the literature.

RESULTS

All five subjects had transmural fibrosis. The mean ADC value with b = 500 was 0.92 ± 0.10 × 10(-3) mm(2)/s and with b = 1000 was 0.8 ± 0.05 × 10(-3) mm(2)/s. There was a significant difference in ADC values between strictures and inflamed-nonstenotic segments (p=0.0143) and between normal and diseased bowel segments (p=0.009-0.0143).

CONCLUSIONS

Quantitative ADC measures of transmural fibrosis are lower compared to the reported values of inflammation in Crohn's disease. To our knowledge, this is the first pediatric pilot study to investigate the correlation of quantitative DWI with histology of surgical specimens in pediatric patients with Crohn's disease. Our results are comparable to a recently published study in adult Crohn's patients showing a significant correlation between a decrease in ADC values and fibrosis.

Longitudinal diffusion-weighted imaging changes in children with small bowel Crohn's disease: preliminary experience

PURPOSE

Crohn's disease has been associated with restricted diffusion in diseased small bowel segments on diffusion-weighted imaging (DWI). However, data addressing longitudinal changes in DWI findings and their potential clinical ramifications in the pediatric population are lacking. The purpose of this study was to follow DWI changes in diseased small bowel segments between serial magnetic resonance enterography (MRE) examinations, and to correlate these changes with other imaging parameters and clinical status.

METHODS

This retrospective study evaluated patients less than 21 years of age undergoing serial MRE examinations including DWI for Crohn's disease involving the small bowel. All patients carried a diagnosis of Crohn's disease established by pathology or corroborative clinical and imaging findings. Longitudinal changes in mean apparent diffusion coefficient (ADC) values within the wall of affected small bowel lesions were recorded and normalized to both unaffected bowel and skeletal muscle. ADC changes were correlated with qualitative imaging phenotype, as reflected by a defined set of non-DWI imaging parameters, as well as with clinical disease activity.

RESULTS

Seventeen lesions were evaluated longitudinally, distributed among 13 patients (9 boys and 4 girls, mean age at baseline 16.6 years), each of whom had two sequential MRE examinations. Lesions demonstrating a fibrostenotic imaging phenotype at follow-up MRE had a significantly lower change in mean ADC value between examinations than lesions that did not have a fibrostenotic imaging phenotype (p = 0.0005), an effect that persisted when ADC values were normalized to unaffected bowel and skeletal muscle. Across all studies, lesions with a fibrostenotic imaging phenotype had lower ADC values than those with an inflammatory imaging phenotype, which were in turn lower than those with a normal imaging phenotype (p = 0.0001).

CONCLUSION

Patterns of longitudinal DWI changes in Crohn's disease may differ among small bowel lesions depending upon their specific natural histories. These findings may assist in the evaluation of the ADC value as a potential imaging surrogate when evaluating lesion status, particularly as it pertains to relative contributions of inflammation and fibrosis.

DWI at MR Enterography for Evaluating Bowel Inflammation in Crohn Disease

OBJECTIVE

The purpose of this article is to provide a comprehensive review regarding DWI enterography used for evaluating Crohn disease and to summarize the relevant evidence.

CONCLUSION

Active bowel inflammation in Crohn disease causes restricted diffusion on MR enterography with DWI. Enterographic DWI to evaluate Crohn disease is increasingly drawing attention for both academic research and clinical practice and has shown potential as a quantitative tool for assessing bowel inflammation. DWI enterography also has multiple unresolved issues and limitations.

Diffusion-weighted Magnetic Resonance Enterography for Evaluating Bowel Inflammation in Crohn's Disease: A Systematic Review and Meta-analysis

BACKGROUND

To systematically determine the performance of diffusion-weighted imaging magnetic resonance enterography (DWI-MRE) for evaluating bowel inflammation in Crohn's disease and sources of heterogeneity between reported results.

METHODS

We identified research studies that investigated DWI-MRE to diagnose bowel inflammation (present versus absent) or to assess bowel inflammatory severity in Crohn's disease by performing a systematic search of PubMed MEDLINE and EMBASE (until March 31, 2015). Study quality was assessed using QUADAS-2. For studies reporting dichotomous diagnosis of bowel inflammation, study heterogeneity and threshold effect were analyzed, summary sensitivity and specificity were estimated, and meta-regression analysis was performed to further explore study heterogeneity. For studies reporting assessment of inflammatory severity, a qualitative summary was performed.

RESULTS

Of 159 articles screened, we found 12 studies (1515 bowel segments) reporting a diagnosis of bowel inflammation and 6 studies (1066 bowel segments) reporting assessment of inflammatory severity. The summary sensitivity and specificity were 92.9% (95% CI, 85.8%-96.6%; I = 87.9%) and 91% (95% CI, 79.7%-96.3%; I = 95.1%), respectively. Sensitivity and false-positive rate were inversely correlated (r = -0.650; P = 0.022). Lack of blinding to contrast-enhanced MRE when interpreting DWI-MRE (P = 0.01) and use of contrast-enhanced MRE as a reference standard (P < 0.01) in some studies were significant factors for study heterogeneity and likely caused overestimation of DWI-MRE accuracy. There was rather clear correlation between diffusion-related parameters and bowel inflammation severity, although the strengths were heterogeneous (correlation coefficient, 0.39-0.98).

CONCLUSIONS

DWI-MRE accuracy was very heterogeneous between studies and was likely overestimated in some studies. Despite rather clear correlation between diffusion-related parameters and bowel inflammatory severity, its strength was variable.

Diffusion weighted imaging in cystic fibrosis disease: beyond morphological imaging

OBJECTIVES

To explore the feasibility of diffusion-weighted imaging (DWI) to assess inflammatory lung changes in patients with Cystic Fibrosis (CF) METHODS: CF patients referred for their annual check-up had spirometry, chest-CT and MRI on the same day. MRI was performed in a 1.5 T scanner with BLADE and EPI-DWI sequences (b = 0-600 s/mm²). End-inspiratory and end-expiratory scans were acquired in multi-row scanners. DWI was scored with an established semi-quantitative scoring system. DWI score was correlated to CT sub-scores for bronchiectasis (CF-CT_BE), mucus (CF-CT_mucus), total score (CF-CT_total-score), FEV₁, and BMI. T-test was used to assess differences between patients with and without DWI-hotspots.

RESULTS

Thirty-three CF patients were enrolled (mean 21 years, range 6-51, 19 female). 4 % (SD 2.6, range 1.5-12.9) of total CF-CT alterations presented DWI-hotspots. DWI-hotspots coincided with mucus plugging (60 %), consolidation (30 %) and bronchiectasis (10 %). DWI_total-score correlated (all p < 0.0001) positively to CF-CT_BE (r = 0.757), CF-CT_mucus (r = 0.759) and CF-CT_total-score (r = 0.79); and negatively to FEV₁ (r = 0.688). FEV₁ was significantly higher (p < 0.0001) in patients without DWI-hotspots.

CONCLUSIONS

DWI-hotspots strongly correlated with radiological and clinical parameters of lung disease severity. Future validation studies are needed to establish the exact nature of DWI-hotspots in CF patients.

KEY POINTS

• DWI hotspots only partly overlapped structural abnormalities on morphological imaging • DWI strongly correlated with radiological and clinical indicators of CF-disease severity • Patients with more DWI hotspots had lower lung function values • Mucus score best predicted the presence of DWI-hotspots with restricted diffusion.

Prospective evaluation of free-breathing diffusion-weighted imaging for the detection of inflammatory bowel disease with MR enterography in childhood population

OBJECTIVE

To evaluate prospectively the performance of diffusion-weighted imaging (DWI) for the detection of active lesions on MR enterography (MRE) in children with inflammatory bowel disease (IBD).

METHODS

MRE of 48 children (mean age 13 years) with suspected or known IBD were blindly analysed by 2 independent readers for the presence of active lesions. Two sets of imaging including DWI and gadolinium-enhanced imaging (GEI) were reviewed. A reader consensus was obtained. The gold standard was histopathological findings. In patient-level analysis and segment-level analysis, sensitivity and specificity were calculated for DWI and GEI and compared using McNemar's test or logistic random-effects models.

RESULTS

At least 1 active lesion was confirmed in 42 (87.5%) children. Sensitivity and specificity for the detection of at least one lesion were 88.1% (95% CI, 74.3-96.1) and 83.3% (95% CI, 35.9-99.6), respectively, for DWI and 66.7% (95% CI, 50.4-80.4) and 83.3% (95% CI, 35.9-99.6), respectively, for GEI. In segment-level analysis, sensitivity and specificity for the detection of specific segment lesions were 62.5% (95% CI, 48.1-75) and 97.1% (95% CI, 93.5-98.7), respectively, for DWI and 45.7% (95% CI, 30.8-61.3) and 98.2% (95% CI, 95.3-99.4), respectively, for GEI. The sensitivity of DWI was significantly better than that of GEI per patient (p = 0.004) and per segment (p = 0.028).

CONCLUSION

DWI demonstrates better performance than GEI for the detection of active lesions in children with IBD.

ADVANCES IN KNOWLEDGE

Examination with no intravenous injection-DWI can replace T1 weighted images when paediatric patients are screened with MRE for IBD. Examination performed in free breathing is better tolerated by children.

Inflammatory bowel disease imaging: Current practice and future directions

The purpose of this paper is to evaluate the role of imaging in inflammatory bowel disease (IBD), including detection of extraluminal complications and extraintestinal manifestations of IBD, assessment of disease activity and treatment response, and discrimination of inflammatory from fibrotic strictures. IBD is a chronic idiopathic disease affecting the gastrointestinal tract that is comprised of two separate, but related intestinal disorders; Crohn’s disease and ulcerative colitis. The paper discusses, in detail the pros and cons of the different IBD imaging modalities that need to be considered in order to optimize the imaging and clinical evaluation of patients with IBD. Historically, IBD evaluation of the bowel has included imaging to assess the portions of the small bowel that are inaccessible to optical endoscopic visualization. This traditionally was performed using barium fluoroscopic techniques; however, cross-sectional imaging techniques (computed tomography and magnetic resonance imaging) are being increasingly utilized for IBD evaluation because they can simultaneously assess mural and extramural IBD manifestations. Recent advances in imaging technology, that continue to improve the ability of imaging to noninvasively follow disease activity and treatment response, are also discussed. This review article summarizes the current imaging approach in inflammatory bowel disease as well as the role of emerging imaging modalities.

Value of diffusion-weighted imaging when added to magnetic resonance enterographic evaluation of Crohn disease in children

BACKGROUND

MR enterography is increasingly utilized for noninvasive evaluation of disease activity in young patients with Crohn disease and has great impact on clinical management. Diffusion-weighted imaging (DWI) is a rapid MR imaging technique that measures molecular diffusion of water and is sensitive to the inflammatory process; however, its value to MR enterography has not been rigorously evaluated.

OBJECTIVE

To determine whether the addition of DWI to MR enterography is helpful in evaluating Crohn disease activity in young patients when compared to a histological reference.

MATERIALS AND METHODS

In this single-institution retrospective study, we searched an imaging database for the period January 2010 to December 2012 to identify patients age 19 years and younger who had MR enterography with diffusion-weighted imaging (DWI). We used an electronic medical record search to identify those who had MR enterography and colonoscopy performed within 28 days of each other. All MR enterography scans were performed on a 1.5-T or 3-T clinical MR scanner with phased-array torso coil configuration using standard pulse sequences as well as axial DWI with b values of 50, 400 and 800. Bowel segments were evaluated for disease activity based on standard MR enterography sequences; in addition, segmental apparent diffusion coefficient (ADC) values were calculated based on DWI. Histological reference for disease activity was based on assessment for mucosal inflammatory changes on endoscopic biopsy. MR enterography and DWI evaluation were performed in a blinded fashion with respect to histological results.

RESULTS

We included imaging of 78 bowel segments from 27 patients (mean age 14.5 ± 3.02 years) with known Crohn disease in the study. The mean ADC for bowel segments with active disease was 1.56 ± 0.7 × 10(3) mm(2)/s compared with 2.58 ± 1.4 × 10(3) mm(2)/s for segments without active disease, a difference that was statistically significant (P < 0.01, Student's t-test). Using a threshold value of 2.0 × 10(3) mm(2)/s, DWI demonstrated lower accuracy (64.1%) but higher sensitivity (78.8%) for detecting active disease compared with standard MR enterography (69.2% and 54.6%, respectively). Combining DWI with MR enterography, using DWI as the initial screen and MR enterography afterward to reduce false negativity, led to a significant increase in accuracy (76.9%; P = 0.03, McNemar's test) compared with either imaging technique alone.

CONCLUSION

Although DWI does not perform as well as standard MR enterography for detection of active Crohn disease, the combination of DWI and MR enterography increases imaging accuracy for determining disease activity compared with either technique alone. These results indicate that DWI adds value to MR enterography and supports the incorporation of DWI into MR enterography protocols for evaluation of Crohn disease in young patients.