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

A comprehensive dataset of magnetic resonance enterography images with intestinal segment annotations

Inflammatory bowel disease (IBD) is a recurrent bowel disease that usually requires magnetic resonance enterography (MRE) for diagnosis and monitoring. However, recognition of bowel segments from MRE images by a radiologist is challenging and time-consuming. Deep learning-based medical image segmentation has shown the potential to reduce manual effort and provide automated tools to assist in disease management; however, it requires a large-scale fine-annotated dataset for training. To address this gap, we collected MRE data, including half-Fourier acquisition single-shot turbo spin-echo(HASTE) sequences with coronal orientation, from 114 patients with IBD, who received 1600-2000 mL of 2.5% mannitol. The bowel images per patient were contoured and annotated into ten segments (stomach, duodenum, small intestine, appendix, cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum), with fine pixel-level annotations labeled by experienced radiologists. Furthermore, we validated the efficiency of several state-of-the-art segmentation methods using this dataset. This study established a high-quality, publicly available whole-bowel segment MR dataset with benchmark results and laid the groundwork for AI research on IBD.

Quantitative Magnetic Resonance Imaging (qMRI) of the Small Bowel in Crohn's Disease: State-of-the-Art and Future Directions

Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal tract in which repeated episodes of acute inflammation may lead to long-term bowel damage. Cross-sectional imaging is used in conjunction with endoscopy to diagnose and monitor disease and detect complications. Magnetic resonance imaging (MRI) has demonstrable utility in evaluating inflammatory activity. However, subjective interpretation of conventional MR sequences is limited in its ability to fully phenotype the underlying histopathological processes in chronic disease. In particular, conventional MRI can be confounded by the presence of mural fibrosis and muscle hypertrophy, which can mask or sometimes mimic inflammation. Quantitative MRI (qMRI) methods provide a means to better differentiate mural inflammation from fibrosis and improve quantification of these processes. qMRI may also provide more objective measures of disease activity and enable better tailoring of treatment. Here, we review quantitative MRI methods for imaging the small bowel in CD and consider the path to their clinical translation. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 2.

Assessment of activity and severity of inflammatory bowel disease in cross-sectional imaging techniques: a systematic review

BACKGROUND AND AIMS

Cross-sectional imaging techniques, including intestinal ultrasonography (IUS), computed tomography enterography (CTE), magnetic resonance enterography (MRE), are increasingly used for the evaluation of inflammatory bowel diseases (IBD). We aimed to systematically review literature evidence on the assessment of disease activity, and/or severity through cross-sectional imaging in IBD patients, and to offer guidance on their most effective utilization.

METHODS

We performed a systematic review of PubMed, EMBASE, and Scopus to identify citations pertaining to the assessment of disease activity and/or severity at cross-sectional imaging techniques compared to a reference standard (ie, other radiological techniques, endoscopy, histopathology, and surgery) in IBD patients published until December 2023.

RESULTS

Overall, 179 papers published between 1990 and 2023 were included, with a total of 10 988 IBD patients (9304 Crohn's disease [84.7%], 1206 ulcerative colitis [11.0%], 38 IBD-U [0.3%], 440 unspecified [4.0%]). Of the 179 studies, 39 investigated IUS, 22/179 CTE, and 101/179 MRE. In the remaining papers, 2 techniques were addressed together. In 81.6% of the papers, endoscopy (with or without histopathology) was used as a reference standard. All studies included evaluated disease activity, while just over half (100/179, 55.8%) also evaluated disease severity of the addressed cross-sectional methodology. Pooled sensitivity, specificity, and overall accuracy of IUS, MRE, and CTE compared to the reference standard were 60%-99%, 60%-100%, and 70%-99%, respectively.

CONCLUSIONS

All cross-sectional imaging techniques demonstrated moderate-to-good accuracy in assessing disease activity and severity of IBD. This finding highlights the potential, especially for MRE and IUS to be widely utilized in managing IBD in both clinical practice and clinical trials.

Intestinal Ultrasound and MRI for Monitoring Therapeutic Response in Luminal Crohn's Disease: A Systematic Review

PURPOSE

Cross-sectional imaging facilitates the assessment of transmural healing in patients with Crohn's disease. This systematic review addresses the utility of MRI and intestinal ultrasound (IUS) in the assessment of disease activity in response to drug therapy compared with endoscopy in patients with luminal Crohn's disease.

METHODS

Database searches were undertaken using predefined terms. Studies with ≥10 patients with luminal Crohn's disease with paired endoscopy and imaging (MRI or IUS) after treatment initiation were included. Publications were identified through searches of six bibliographic databases, all run on June 24, 2022. Records were screened on title and abstract, then full text, by two independent reviewers.

RESULTS

In total, 5,760 records were identified, with 24 studies meeting the inclusion criteria. Ten studies examined IUS and found good correlation between IUS and endoscopic remission (κ = 0.63-0.73). Early reduction in bowel wall thickness at 4 to 8 weeks predicted endoscopic response at 12 to 38 weeks (area under the receiver operating characteristic curve [AUROC], 0.77; odds ratio, 10.8; P = .01). Twelve studies examined MRI, with the Magnetic Resonance Index of Activity score having high accuracy for predicting endoscopic remission (AUROC, 0.97; sensitivity, 93%; specificity, 77%). A Simplified Magnetic Resonance Index of Activity score cutoff of ≥1 identifies active endoscopic disease (AUROC, 0.92; 95% confidence interval, 0.88-0.95; P < .0001).

CONCLUSIONS

IUS and MRI are both reliable, noninvasive modalities for assessing transmural healing in patients with Crohn's disease and are accurate in monitoring the response to drug therapy. These modalities can be used to monitor response to biologic induction therapy, with early changes predictive of response to treatment.

ADC Values for Detecting Bowel Inflammation and Biologic Therapy Response in Patients With Crohn Disease: A Post Hoc Prospective Trial Analysis

BACKGROUND. New biologic agents for Crohn disease (CD) create a need for noninvasive disease markers. DWI may assess bowel inflammation without contrast agents. OBJECTIVE. The purpose of this study was to evaluate ADC values for identifying bowel inflammation and therapeutic response in patients with CD treated with biologic therapy. METHODS. This study entailed post hoc analysis of prospective trial data. Analysis included 89 patients (median age, 37 years; 49 women, 40 men) with CD treated by biologic therapy who underwent MR enterography (MRE) at baseline and 46 weeks after therapy, from March 2013 to April 2021; 43 patients underwent ileocolonoscopy at both time points. Analysis was conducted at the level of small-bowel and colorectal segments (586 segments analyzed). MR index of activity (MaRIA) score and presence of endoscopic ulcers were determined at both time points. One observer measured bowel wall ADC. Diagnostic performance was evaluated. Dichotomous ADC assessments used a threshold of 1301 × 10-6 mm2/s based on initial ROC analysis; dichotomous MaRIA score assessments used a threshold of 11 (moderate to severe inflammation). A second observer repeated ADC measurements in 15 patients. RESULTS. At baseline, ADC had AUC of 0.92, sensitivity of 78.6%, specificity of 91.4%, and accuracy of 88.2% for detecting segments with MaRIA score 11 or greater. At baseline, AUC for detecting endoscopic ulcers was 0.96 for MaRIA score versus 0.87 for ADC (p < .001); sensitivity, specificity, and accuracy were 70.8%, 90.2%, and 85.1% for ADC and 86.2%, 96.2%, and 93.6% for MaRIA score. At follow-up, ADC had AUC of 0.87, sensitivity of 75.4%, specificity of 83.6%, and accuracy of 80.0% for detecting improvement in MaRIA score to less than 11. At follow-up, AUC for detecting endoscopic ulcer healing was 0.94 for MaRIA score versus 0.84 for ADC (p = .01); sensitivity, specificity, and accuracy were 70.7%, 95.8%, and 84.4% for ADC and 90.2%, 100.0%, and 95.6% for MaRIA score. Interobserver agreement for ADC, based on intraclass correlation coefficient, was 0.70 at baseline and 0.65 at follow-up. CONCLUSION. The findings do not support use of ADC rather than MaRIA scores for detecting biologic therapy response. CLINICAL IMPACT. ADC may have an adjunct role in assessing bowel inflammation in CD, but showed limited performance for detecting biologic therapy response.

Role of abbreviated non-contrast-enhanced MR-enterography in the evaluation of Crohn's disease activity and complications as an alternative for full protocol contrast-enhanced study: A systematic review and meta-analysis

Background

Crohn's disease (CD) is a chronic disorder that often starts at a young age and involves periods of remission and relapse. Prompt diagnosis of relapses through screening is crucial due to the potential morbid complications of untreated active inflammation. Magnetic resonance enterography (MRE) is a noninvasive technique to screen for active inflammation. The standard protocol involves intravenous injection of contrast agents with potential side effects. Some abbreviated non-contrast-enhanced MRE protocols are proposed as alternatives for conventional MRE to identify active inflammation. Currently, there is controversy regarding the applicability and accuracy of these protocols. This study aims to describe and compare these protocols and evaluate their accuracy in detecting active inflammation and CD complications.

Methods

Results from a systematic search of three databases in August 2022 were queried and screened by abstract and full text. Eligible studies were qualitatively and quantitatively analyzed by diagnostic test accuracy meta-analysis.

Results

59 studies entered the systematic review, and 37 were eligible for meta-analysis. Diffusion-weighted imaging (DWI) and fast T2-weighted (T2w) sequences were most frequently used in abbreviated protocols and showed non-inferior accuracy compared to the full protocol in detecting active inflammation. ADC and qualitative DWI had pooled sensitivity of 90% (CI: 82-95%) and 89% (CI:82-93%) and pooled specificity of 94% (CI: 88-97%) and 89% (CI: 79-94%), respectively for detecting active inflammation. Moreover, T2w and combined T2w+DWI sequences had pooled sensitivity of 80% (CI: 64-90%) and 76% (CI: 61-86%) and pooled specificity of 90% (CI: 80-95%) and 87% (CI: 74 - 94%), respectively. Unenhanced protocols show relatively poor diagnostic accuracy in detecting penetrating complications of CD. Magnetization transfer imaging (MTI) has demonstrated excellent accuracy in detecting fibrosis. High heterogeneity was observed in all subgroups, and accuracy was reported to be highly operator dependent in most studies.

Conclusion

An abbreviated protocol consisting of DWI and fast T2w imaging can potentially replace the full protocol MRE. Full protocol MRE will still have its role in identifying penetrating complications. MTI should be indicated in case of suspected fibrostenotic disease.

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.

Cross-Sectional Imaging Instead of Colonoscopy in Inflammatory Bowel Diseases: Lights and Shadows

International guidelines recommend a treat-to-target strategy with a close monitoring of disease activity and therapeutic response in inflammatory bowel diseases (IBD). Colonoscopy (CS) represents the current first-line procedure for evaluating disease activity in IBD. However, as it is expensive, invasive and poorly accepted by patients, CS is not appropriate for frequent and repetitive reassessments of disease activity. Recently, cross-sectional imaging techniques have been increasingly shown as reliable tools for assessing IBD activity. While computed tomography (CT) is hampered by radiation risks, routine implementation of magnetic resonance enterography (MRE) for close monitoring is limited by its costs, low availability and long examination time. Novel magnetic resonance imaging (MRI)-based techniques, such as diffusion-weighted imaging (DWI), can overcome some of these weaknesses and have been shown as valuable options for IBD monitoring. Bowel ultrasound (BUS) is a noninvasive, highly available, cheap, and well accepted procedure that has been demonstrated to be as accurate as CS and MRE for assessing and monitoring disease activity in IBD. Furthermore, as BUS can be quickly performed at the point-of-care, it allows for real-time clinical decision making. This review summarizes the current evidence on the use of cross-sectional imaging techniques as cost-effective, noninvasive and reliable alternatives to CS for monitoring patients with IBD.

Is the Mixed Use of Magnetic Resonance Enterography and Computed Tomography Enterography Adequate for Routine Periodic Follow-Up of Bowel Inflammation in Patients with Crohn's Disease?

OBJECTIVE

Computed tomography enterography (CTE) and magnetic resonance enterography (MRE) are considered substitutes for each other for evaluating Crohn's disease (CD). However, the adequacy of mixing them for routine periodic follow-up for CD has not been established. This study aimed to compare MRE alone with the mixed use of CTE and MRE for the periodic follow-up of small bowel inflammation in patients with CD.

MATERIALS AND METHODS

We retrospectively compared two non-randomized groups, each comprising 96 patients with CD. One group underwent CTE and MRE (MRE followed by CTE or vice versa) for the follow-up of CD (interval, 13-27 months [median, 22 months]), and the other group underwent MRE alone (interval, 15-26 months [median, 21 months]). However, these two groups were similar in clinical characteristics. Three independent readers from three different institutions determined whether inflammation had decreased, remained unchanged, or increased within the entire small bowel and the terminal ileum based on sequential enterography of the patients after appropriate blinding. We compared the two groups for inter-reader agreement and accuracy (terminal ileum only) using endoscopy as the reference standard for enterographic interpretation.

RESULTS

The inter-reader agreement was greater in the MRE alone group for the entire small bowel (intraclass correlation coefficient [ICC]: 0.683 vs. 0.473; p = 0.005) and the terminal ileum (ICC: 0.656 vs. 0.490; p = 0.030). The interpretation accuracy was higher in the MRE alone group without statistical significance (70.9%-74.5% vs. 57.9%-64.9% in individual readers; adjusted odds ratio = 3.21; p = 0.077).

CONCLUSION

The mixed use of CTE and MRE was inferior to MRE alone in terms of inter-reader reliability and could probably be less accurate than MRE alone for routine monitoring of small bowel inflammation in patients with CD. Therefore, the consistent use of MRE is favored for this purpose.

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.

Emerging Imaging Biomarkers in Crohn Disease

ABSTRACT

In this review article, we present the latest developments in quantitative imaging biomarkers based on magnetic resonance imaging (MRI), applied to the diagnosis, assessment of response to therapy, and assessment of prognosis of Crohn disease. We also discuss the biomarkers' limitations and future prospects. We performed a literature search of clinical and translational research in Crohn disease using diffusion-weighted MRI (DWI-MRI), dynamic contrast-enhanced MRI (DCE-MRI), motility MRI, and magnetization transfer MRI, as well as emerging topics such as T1 mapping, radiomics, and artificial intelligence. These techniques are integrated in and combined with qualitative image assessment of magnetic resonance enterography (MRE) examinations. Quantitative MRI biomarkers add value to MRE qualitative assessment, achieving substantial diagnostic performance (area under receiver-operating curve = 0.8-0.95). The studies reviewed show that the combination of multiple MRI sequences in a multiparametric quantitative fashion provides rich information that may help for better diagnosis, assessment of severity, prognostication, and assessment of response to biological treatment. However, the addition of quantitative sequences to MRE examinations has potential drawbacks, including increased scan time and the need for further validation before being used in therapeutic drug trials as well as the clinic.

MR-enterography in Crohn's disease: what MRE mural parameters are associated to one-year therapeutic management outcome?

OBJECTIVE

To investigate the association of mural parameters of MR-enterography (MRE) with one-year therapeutic management of Crohn's disease (CD) patients.

METHODS

CD patients, undergone MRE with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps between January 2017 and June 2018, were retrospectively enrolled. Extramural complications represented an exclusion criterion because of their potential influence on the intrinsic characteristic of the bowel wall. Two groups of patients were defined on the base of the therapeutic management adopted at 1-year follow-up: Medical-group and surgical-group. The following MRE parameters were evaluated: wall-thickening, longitudinal-extension, T2-fat-suppression-mural-signal, ulcers, mural-oedema, wall-enhancement-rate/pattern, DWI-scores, ADC-values, strictures.

RESULTS

70 CD patients were enrolled. 57/70 (81.4%) were included in Medical-group and 13/70 (18.6%) in Surgical-group. ADCmean and strictures resulted to be significantly (p < 0.01) different between the two groups. The ADCmean showed to be significantly associated to conservative management [p < 0.01; OR: 0.0003; 95% CI (0.00-0.13)], while the strictures to surgical management [p < 0.01; OR: 29.7; 95% CI (4.9-179.7)]. ROC curves for ADCmean showed that AUC was 0.717 [95% CI (0.607-0.810), p < 0.01] with an optimal cut-off value of 1.081 × 10^-3 mm² s^-1. A negative predictive value of 90.2% was observed associating ADCmean values > 1.081 × 10^-3 mm² s^-1 to conservative therapy. 13/17 (76%) strictures with an ADCmean > 1.081 × 10^-3 mm² s^-1 benefited of conservative therapy.

CONCLUSION

ADCmean values calculated on DWI-MRE may be associated to 1-year conservative medical therapy in patients with CD without extramural complications.

ADVANCES IN KNOWLEDGE

ADC maps may be proposed to select CD patients with a lower burden of mural active inflammatory cells and/or fibrosis benefiting of 1-year conservative treatment.

Early Transmural Response Assessed Using Magnetic Resonance Imaging Could Predict Sustained Clinical Remission and Prevent Bowel Damage in Patients with Crohn's Disease Treated with Anti-Tumour Necrosis Factor Therapy

BACKGROUND

Magnetic resonance imaging [MRI] is a promising tool to evaluate therapeutic efficacy in ileocolonic Crohn's disease [CD].

AIMS

We aimed to assess the feasibility of early MRI evaluation (week 12 [W12]) to predict corticosteroid-free remission [CFREM] at W52 and prevent long-term bowel damage.

METHODS

All patients with active CD needing anti-tumour necrosis factor [anti-TNF] therapy were consecutively enrolled in this multicentre prospective study. MRI was performed before starting therapy, at W12 and W52. CFREM was defined as Crohn's Disease Activity Index < 150, C-reactive protein < 5 mg/L and faecal calprotectin < 250 µg/g, with no switch of anti-TNF agents, no bowel resection and no therapeutic intensification between W12 and W52.

RESULTS

Among 46 patients, 22 [47.8%] achieved CFREM at W52. Anti-TNF agents were able to heal almost all CD lesions as soon as W12 [p < 0.05]. Early transmural response defined as a 25% decrease of either Clermont score (odds ratio [OR] = 7.7 [1.7-34.0], p < 0.001) or Magnetic Resonance Index of Activity (OR = 4.2 [1.3-13.3], p = 0.015) was predictive of CFREM at W52. Achieving at least two items on W12-MRI among ulceration healing, disappearance of enlarged lymph nodes or sclerolipomatosis, ΔADC [apparent diffusion coefficient] > +10% or ΔRCE [relative contrast enhancement] > -30% was associated with a likelihood of CFREM at W52 of 84.6% vs 37.5% in patients without transmural response [p < 0.001]. Early transmural response could prevent bowel damage progression over time using Clermont score (hazard ratio = 0.21 [0.0-0.9]; p = 0.037).

CONCLUSION

Evaluation of early transmural response by MRI is feasible and is a promising end point to monitor therapeutic efficacy in patients with CD.

Use of Cross-Sectional Imaging for Tight Monitoring of Inflammatory Bowel Diseases

A treat-to-target strategy with close monitoring of intestinal inflammation is recommended in inflammatory bowel disease (IBD). Ileocolonoscopy remains the gold standard for assessing disease activity in IBD but is a relatively invasive procedure and is impossible to repeat in the context of tight monitoring strategies. In addition to biomarkers, cross-sectional imaging increasingly is used in these patients. Computed tomography is limited by the use of radiation, while the use of magnetic resonance enterography (MRE) is limited by its cost and access. There is growing interest in bowel ultrasound that represents a cost-effective, noninvasive, and well-tolerated modality in clinical practice, but it is operator dependent. Compared with ileocolonoscopy and MRE, bowel US has been shown to have the same level of accuracy in assessing and monitoring disease activity for both CD and UC and thus can be considered a point-of-care test. Diffusion-weighted imaging (DWI) is a MR imaging technique that increasingly is used in both IBD and non-IBD conditions and has been shown to be a valuable and accurate tool for assessing and monitoring IBD activity. Compared with conventional MRE, DWI is quicker, less time consuming, may not require intravenous contrast agent, fasting, bowel cleansing, oral preparation, or rectal preparation. This review discusses the role of these cross-sectional imaging techniques for the management of patients with IBD. In the near future, the value of DWI and ultrasound in assessing IBD will require further investigation in the era of transmural healing in CD and complete mucosal healing, including histologic remission, in ulcerative colitis.

Evaluating inflammatory activity in Crohn's disease by cross-sectional imaging techniques

The evaluation of inflammatory bowel activity in patients with Crohn’s disease has traditionally been a challenge, mainly because of the difficulty in gaining endoscopic access to the small bowel. Historically, barium-based contrast studies were the only option for the evaluation of inflammatory activity in Crohn’s disease. They were gradually replaced by cross-sectional imaging techniques, computed tomography enterography (CTE) and magnetic resonance enterography (MRE) now being the modalities of choice for such evaluations. Those two imaging methods have provided important information regarding intestinal wall involvement and extra-intestinal manifestations of Crohn’s disease, not only assessing lesion characteristics and complications but also quantifying inflammatory bowel activity. The objective of this article is to review the main technical aspects of CTE and MRE, together with their indications, contraindications, and limitations, as well as the CTE and MRE imaging characteristics of inflammatory activity in Crohn’s disease.

Radiologische Diagnostik chronisch-entzündlicher Darmerkrankungen bei Kindern und Jugendlichen

Dank der technischen Fortschritte nehmen bildgebende Methoden eine immer wichtigere Rolle sowohl in der Diagnostik als auch im klinischen Management chronisch-entzündlicher Darmerkrankungen (CED), insbesondere in der Pädiatrie, ein. Dieser Beitrag fokussiert charakteristische Erscheinungsformen der CED und jeweils relevante bildgebende Verfahren (Ultraschall und MRT). Außerdem werden Forschungstrends und aktueller Wissensstand zu verschiedenen bildgebenden Modalitäten dargestellt.

Comparison of Three Magnetization Transfer Ratio Parameters for Assessment of Intestinal Fibrosis in Patients with Crohn's Disease

OBJECTIVE

To establish a novel standardized magnetization transfer ratio (MTR) parameter which considers the element of the normal bowel wall and to compare the efficacy of the MTR, normalized MTR, and standardized MTR in evaluating intestinal fibrosis in Crohn's disease (CD).

MATERIALS AND METHODS

Abdominal magnetization transfer imaging from 20 consecutive CD patients were analyzed before performing elective operations. MTR parameters were calculated by delineating regions of interest in specified segments on MTR maps. Specimens with pathologically confirmed bowel fibrosis were classified into one of four severity grades. The correlation between MTR parameters and fibrosis score was tested by Spearman's rank correlation. Differences in MTR, normalized MTR, and standardized MTR across diverse histologic fibrosis scores were analyzed using the independent sample t test or the Mann-Whitney U test. The area under the receiver operating characteristic curve (AUC) was computed to test the efficacies of the MTR parameters in differentiating severe intestinal fibrosis from mild-to-moderate fibrosis.

RESULTS

Normalized (r = 0.700; p < 0.001) and standardized MTR (r = 0.695; p < 0.001) showed a strong correlation with bowel fibrosis scores, followed by MTR (r = 0.590; p < 0.001). Significant differences in MTR (t = -4.470; p < 0.001), normalized MTR (Z = -5.003; p < 0.001), and standardized MTR (Z = -5.133; p < 0.001) were found between mild-to-moderate and severe bowel fibrosis. Standardized MTR (AUC = 0.895; p < 0.001) had the highest accuracy in differentiating severe bowel fibrosis from mild-to-moderate bowel wall fibrosis, followed by normalized MTR (AUC = 0.885; p < 0.001) and MTR (AUC = 0.798; p < 0.001).

CONCLUSION

Standardized MTR is slightly superior to MTR and normalized MTR and therefore may be an optimal parameter for evaluating the severity of intestinal fibrosis in CD.

Can ADC be used as a surrogate marker of response to therapy in intestinal tuberculosis?

PURPOSE

To evaluate the utility of Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) in assessing treatment response in patients of intestinal tuberculosis (ITB).

METHOD AND MATERIALS

MR Enterography (MRE) was done for patients with suspicion of ITB and 19 patients with pre- and post-treatment imaging were included in the analysis. MRE included T1W, T2W, post-contrast T1W, and DWI sequences. DWI was done using b values-0, 400 and 800 s/mm², and ADC maps were generated. The trace DW images and ADC values were compared before and after therapy. Composite gold standard (clinical, colonoscopic criteria, and biopsy) was used to assess treatment response and to classify into no response, partial response, and complete response.

RESULTS

Thirty-one bowel segments were evaluated at baseline and after treatment in 19 patients. Prior to therapy, restricted diffusion was seen in 29/31 (93.5%) segments. After treatment, patients with either complete or partial response (27/31 segments, 15 patients) showed significant rise in mean ADC values from 1.1 ± 0.37 × 10^-3 to 2.1 ± 0.64 × 10^-3 mm²/s (p value < 0.05), whereas no significant change was found in mean ADC values of non-responders (4/29 segments in 4 patients) which increased from 1.0 ± 0.1 × 10^-3 mm²/s on baseline scan to 1.32 ± 0.2 × 10^-3 mm²/s on post-treatment scan (p value = 0.318). An increase in ADC value was found to be a reliable and objective marker of improvement with response to therapy.

CONCLUSION

ADC values show good correlation with treatment response in ITB and can be used for objectively quantifying it.

Potential of diffusion-weighted imaging in magnetic resonance enterography to identify neoplasms in the ileocecal region: Use of ultra-high b-value diffusion-weighted imaging

Patients with chronic inflammatory bowel disease have an increased risk of colorectal cancer, and the differentiation between neoplastic and inflammatory lesions often poses a clinical dilemma. The aim of the present study was to investigate whether diffusion-weighted (DW) magnetic resonance (MR) enterography with ultra-high b-value facilitates the identification of neoplastic lesions in the ileocecal region. A total of 76 patients (22 patients with neoplasms, 26 inflammatory lesions and 28 normal subjects) from 292 cases of suspected bowel disorders were included in the present study. All patients were examined with conventional MR enterography and DW imaging (DWI) with seven different b-values (400, 600, 800, 1,000, 1,200, 1,500 and 3,000 sec/mm²) in a 3T MR scanner. DWI scans with different b-values were analyzed independently by two radiologists for the presence of ileocecal lesions. The signal intensity of the majority of inflammatory lesions and normal bowel segments gradually decreased to the background intensity with increasing b-values; however, neoplastic lesions demonstrated relative hyperintensity compared with the background. In addition, ~76% of the positive findings from b=3,000 sec/mm² DWI were neoplasms. In conclusion, a lesion with consistently high signal intensity from DWI images with b-values increasing to 3,000 sec/mm² indicated the presence of neoplasms. The results suggested that ultra-high b-value (3,000 sec/mm²) imaging may aid the clinical differentiation of neoplasms from benign conditions.

Quantitative diffusion-weighted magnetic resonance enterography in ileal Crohn's disease: A systematic analysis of intra and interobserver reproducibility

BACKGROUND

Magnetic resonance enterography (MRE) is increasingly attractive as a noninvasive and radiation-free tool for assessing Crohn's disease (CD). Diffusion-weighted imaging (DWI) is recommended as an optional MRE sequence for CD by the European Society of Gastrointestinal and Abdominal Radiology, and has shown a superb potential as a quantitative modality for bowel inflammation evaluation. However, the measurement reproducibility of quantitative DWI analysis in MRE has not been ascertained so far. To facilitate the application of quantitative diffusion-weighted MRE in the clinical routine, systematic investigations of the intra and interobserver reproducibility of DWI quantitative parameters should be performed.

AIM

To evaluate the intra and interobserver reproducibility of quantitative analysis for diffusion-weighted MRE (DW-MRE) in ileal CD.

METHODS

Forty-four subjects (21 with CD and 23 control subjects) who underwent ileocolonoscopy and DW-MRE (b = 800 s/mm2) within one week were included. Two radiologists independently measured apparent diffusion coefficients (ADC) of the terminal ileum and signal intensity ratio (SR) of the terminal ileum to ipsilateral psoas muscle on DWI images (b = 800 s/mm2). Between- and within-reader agreements were assessed using intraclass correlation coefficients (ICC), coefficients of variation (CoV), and 95% limits of agreement of Bland-Altman plots (BA-LA LoA). Diagnostic performances of ADC and SR for identifying inflamed terminal ileum from the normal were evaluated by receiver operating characteristic (ROC) curve analysis.

RESULTS

There were no significant differences in ADC or SR values between the two sessions or between the two radiologists either in the CD or control group (paired t-test, P > 0.05). The intra and interobserver reproducibility of ADC (ICC: 0.952-0.984; CoV: 3.73-6.28%; BA-LA LoA: ±11.27% to ±15.88%) and SR (ICC: 0.969-0.989; CoV: 3.51%-4.64%; BA-LA LoA: ±10.62% to ±15.45%) was excellent for CD. Agreement of ADC measurements was slightly less in control subjects (ICC: 0.641-0.736; CoV: 10.47%-11.43%; BA-LA LoA: ± 26.59% to ± 30.83%). SR of normal terminal ileum demonstrated high intra and interobserver reproducibility (ICC: 0.944-0.974; CoV: 3.73%-6.28%; BA-LA LoA: ± 18.58% to ± 24.43%). ADC and SR of two readers had outstanding diagnostic efficiencies (area under the ROC curve: 0.923-0.988).

CONCLUSION

Quantitative parameters derived from DW-MRE have good to excellent intra and interobserver agreements with high diagnostic accuracy, and can serve as robust and efficient quantitative biomarkers for CD evaluation.

Magnetic resonance enterography features of small bowel Crohn's disease activity: an inter-rater reliability study of small bowel active inflammation in clinical practice setting

OBJECTIVE

The aim of this study is to determine the interrater agreement in a clinical practice environment for the most commonly used magnetic resonance enterography (MRE) features of Crohn's disease (CD).

METHODS

CD patients with MRE's before and after treatment were retrospectively identified using search queries over a 7-year period (May 2017-September 2017). MRE features of CD comprising components of multiple CD scoring indices were scored by radiologists in the same segment of bowel. Agreement for nominal categorical and continuous variables was assessed using a κ and interclass correlation coefficients, respectively.

RESULTS

80 scans comprised the study population. Moderate interrater agreement was seen in both the pre- and post-treatment MRE's for presence of diffusion restriction (к = 0.43, 0.48; pre- and post-treatment), stricturing disease (к = 0.51, 0.52), overall degree of severity (к = 0.49, 0.59). Substantial agreement was seen in pre- and post-treatment scans for length of involvement (interclass correlation coefficient = 0.67, 0.61). The presence of mucosal ulceration had no agreement (к = -0.07, -0.042).

CONCLUSION

Many MRE features of active CD comprising the major CD scoring indices are reproducible when interpreted by non-CD focused abdominal radiologists. However, the presence of mucosal ulcerations had no agreement and may need more investigation before including this feature as a driver in therapeutic decision making.

ADVANCES IN KNOWLEDGE

Demonstrates the unreliability of mucosal ulceration by non-CD focused abdominal radiologists, targeting a potential area for future education. Key Points The majority of MRE findings incorporated in to many CD scoring indices have fair to moderate inter-rater agreement even when read by non-MRE expert radiologists. Substantial agreement was seen in the length of involved bowel, but this feature is only incorporated in to one of the CD scoring indices. Presence of mucosal ulcerations had no interrater agreement in our study-a feature which is heavily weighted by several CD scoring indices. Research should be focused bridging those features which have poor interrater agreement.

Bowel wall healing assessed using magnetic resonance imaging predicts sustained clinical remission and decreased risk of surgery in Crohn's disease

BACKGROUND

Endoscopic mucosal healing is considered as the best therapeutic target in Crohn's disease (CD) as it is associated with better long-term outcomes. We investigated whether bowel wall healing (BWH) assessed using magnetic resonance imaging (MRI) could predict favorable outcomes and could be a potential therapeutic target.

METHODS

We performed a post hoc analysis from two prospective studies (n = 174 patients). All the patients with previous objective signs of bowel inflammation and assessed by MRI for therapeutic efficacy had a standardized and blinded evaluation, and underwent MRI. Complete BWH was defined as no segmental MaRIA > 7 or no segmental Clermont score > 8.4 and BWH as no segmental MaRIA > 11 or no segmental Clermont score > 12.5. Clinical corticosteroid-free remission (CFREM) was defined as no reappearance or worsening of clinical manifestation leading to therapeutic modification, hospitalization or CD-related surgery. Multivariate analyses were performed including all the relevant parameters.

RESULTS

Overall, 63 patients with CD were included (mean follow-up = 4.8 ± 3.1 semesters). In multivariate analysis (n = 303 semesters), complete BWH or BWH was associated with sustained CFREM according to MaRIA [OR = 4.42 (2.29-26.54); p = 0.042 and OR = 3.43 (1.02-27.02); p = 0.047, respectively] or Clermont score [OR = 3.09 (1.01-12.91); p = 0.049 and OR = 3.88 (1.40-13.80); p = 0.036, respectively]. In multivariate analysis (n = 63 patients), complete BWH or BWH was associated with decreased risk of surgery using MaRIA [HR = 0.16 (0.043-0.63); p = 0.008 and HR = 0.24 (0.07-0.77); p = 0.017, respectively] or Clermont score [HR = 0.24 (0.07-0.78); p = 0.016 and HR = 0.23 (0.07-0.76); p = 0.016, respectively].

CONCLUSIONS

MRI endpoints are predictive of favorable outcomes after medical therapy and could be used as therapeutic target in daily practice and clinical trials.

Comparison of contrast-enhanced and diffusion-weighted MRI in assessment of the terminal ileum in Crohn's disease patients

PURPOSE

The purpose of the study was to compare the performance of contrast-enhanced (CE)-MRI and diffusion-weighted imaging (DW)-MRI in grading Crohn's disease activity of the terminal ileum.

METHODS

Three readers evaluated CE-MRI, DW-MRI, and their combinations (CE/DW-MRI and DW/CE-MRI, depending on which protocol was used at the start of evaluation). Disease severity grading scores were correlated to the Crohn's Disease Endoscopic Index of Severity (CDEIS). Diagnostic accuracy, severity grading, and levels of confidence were compared between imaging protocols and interobserver agreement was calculated.

RESULTS

Sixty-one patients were included (30 female, median age 36). Diagnostic accuracy for active disease for CE-MRI, DW-MRI, CE/DW-MRI, and DW/CE-MRI ranged between 0.82 and 0.85, 0.75 and 0.83, 0.79 and 0.84, and 0.74 and 0.82, respectively. Severity grading correlation to CDEIS ranged between 0.70 and 0.74, 0.66 and 0.70, 0.69 and 0.75, and 0.67 and 0.74, respectively. For each reader, CE-MRI values were consistently higher than DW-MRI, albeit not significantly. Confidence levels for all readers were significantly higher for CE-MRI compared to DW-MRI (P < 0.001). Further increased confidence was seen when using combined imaging protocols.

CONCLUSIONS

There was no significant difference of CE-MRI and DW-MRI in determining disease activity, but the higher confidence levels may favor CE-MRI. DW-MRI is a good alternative in cases with relative contraindications for the use of intravenous contrast medium.

Age of Data in Contemporary Research Articles Published in Representative General Radiology Journals

Objective

To analyze and compare the age of data in contemporary research articles published in representative general radiology journals.

Materials and Methods

We searched for articles reporting original research studies analyzing patient data that were published in the print issues of the Korean Journal of Radiology (KJR), European Radiology (ER), and Radiology in 2017. Eligible articles were reviewed to extract data collection period (time from first patient recruitment to last patient follow-up) and age of data (time between data collection end and publication). The journals were compared in terms of the proportion of articles reporting the data collection period to the level of calendar month and regarding the age of data.

Results

There were 50, 492, and 254 eligible articles in KJR, ER, and Radiology, respectively. Of these, 44 (88%; 95% confidence interval [CI]: 75.8-94.8%), 359 (73%; 95% CI: 68.9-76.7%), and 211 (83.1%; 95% CI: 78-87.2%) articles, respectively, provided enough details of data collection period, revealing a significant difference between ER and Radiology (p = 0.002). The age of data was significantly greater in KJR (median age: 826 days; range: 299-2843 days) than in ER (median age: 570 days; range: 56-4742 days; p < 0.001) and Radiology (median age: 618; range: 75-4271 days; p < 0.001).

Conclusion

Korean Journal of Radiology did not fall behind ER or Radiology in reporting of data collection period, but showed a significantly greater age of data than ER and Radiology, suggesting that KJR should take measures to improve the timeliness of its data.

Treat-to-target in Crohn's disease: Will transmural healing become a therapeutic endpoint?

Crohn's disease (CD) represents a chronic transmural inflammatory condition of the gastrointestinal tract, which usually leads to structural damage and significant disability. Deep remission - defined by both clinical and endoscopic remission, signifying mucosal healing - represents the current endpoint in the treat-to-target strategy, significantly improving patients' long-term outcomes. Transmural healing (TH) could be a more effective target, but this possibility remains unclear. This narrative review aims to critically review and summarize the available literature relating TH to long-term outcomes, being the first of its kind and to the best of the author's knowledge. A systematic literature search (from inception to March 31 2018) was performed, using multiple databases, and identifying seven full-text manuscripts. In those studies, long-term favorable outcomes (≥ 52 wk) included sustained clinical remission, as well as fewer therapeutic changes, CD-related hospitalizations, and surgeries. Despite heterogeneous design and methodological limitations, six of the studies demonstrated that TH or intestinal healing (TH plus mucosal healing) were predictive for the aforementioned favorable outcomes. Therefore, TH may become a reasonable therapeutic target and be included in the concept of deep remission. Further prospective, well-designed, multicenter trials aiming to better define the role of TH in personalized therapy for CD and to determine the long-term influence of TH on bowel damage and disability are warranted.

Computed Tomography and Magnetic Resonance Small Bowel Enterography: Current Status and Future Trends Focusing on Crohn's Disease

Computed tomography enterography (CTE) and magnetic resonance enterography (MRE) are presently state-of-the-art radiologic tests used to examine the small bowel for various indications. This article focuses on CTE and MRE for the evaluation of Crohn disease. The article describes recent efforts to achieve more standardized interpretation of CTE and MRE, summarizes recent research studies investigating the role and impact of CTE and MRE more directly for several different clinical and research issues beyond general diagnostic accuracy, and provides an update on progress in imaging techniques. Also addressed are areas that need further exploration in the future.

New cross-sectional imaging in IBD

PURPOSE OF REVIEW

Cross-sectional imaging, namely ultrasound, CT and MR enterography, complements clinical and endoscopic monitoring of activity and complications in IBD, and emerging new radiological technologies may have clinical applications in the near future. This review offers an update on the potential role of these new imaging methods in the management of IBD.

RECENT FINDINGS

Specific MR techniques [diffusion-weighted imaging (DWI), diffusion kurtosis imaging (DKI) and magnetization transfer] allow accurate detection of inflammation (DWI and maybe DKI) and fibrosis (magnetization transfer) in Crohn's disease, without the need of intravenous gadolinium administration. ultrasonography developments (elastography, contrast-enhanced ultrasonography, small intestine contrast ultrasonography and multispectral optoacoustic tomography) are promising techniques for evaluation of fibrosis (elastography) and inflammation (contrast ultrasonography). Dose-reduction techniques in CT allow similar quality imaging and diagnostic accuracy with lower radiation exposure. Hybrid imaging (PET/MR and PET/CT) hold promise for grading inflammation in Crohn's disease.

SUMMARY

The potential benefits of new cross-sectional imaging techniques in IBD include better inflammation grading, such as identification of mild degree of activity, which may be relevant whenever assessing response to treatment and, of uttermost importance, accurate preoperative detection and grading of fibrosis in stricturing Crohn's disease, facilitating surgical vs. medical therapeutic decisions.

A review of magnetic resonance enterography-based indices for quantification of Crohn's disease inflammation

Magnetic resonance enterography (MRE) is a leading radiological modality in Crohn's disease (CD) and is used together with laboratory findings and endoscopic examinations for the evaluation of patients during initial diagnosis and follow up. Over the years, there has been great progress in the understanding of CD and there is a continuous strive to achieve better monitoring of patients and to develop new modalities which will predict disease course and thus help in clinical decisions making. An objective evaluation of CD using a quantification score is not a new concept and there are different clinical, endoscopies, radiological and combined indices which are used in clinical practice. Such scores are a necessity in clinical trials on CD for evaluation of disease response, however, there is no consensus of the preferred MRE score and they are not routinely used. This review presents MRE-based indices in use in the last decade: the Magnetic Resonance Index of Activity (MaRIA), the Clermont score, the Crohn's Disease Magnetic Resonance Imaging (MRI) Index (CDMI), the Magnetic Resonance Enterography Global Score (MEGS) and the Lemann index. We compare the different indices and evaluate the clinical research that utilized them. The aim of this review is to provide a reference guide for researchers and clinicians who incorporate MRE indices in their work. When devising future indices, accumulated data of the existing indices must be taken into account, as each of the current indices has its own strengths and weakness.

CT Enterography for Surveillance of Anastomotic Recurrence within 12 Months of Bowel Resection in Patients with Crohn's Disease: An Observational Study Using an 8-Year Registry

OBJECTIVE

To investigate the diagnostic yield and accuracy of CT enterography (CTE) for early (< 12 postoperative months) surveillance of anastomotic recurrence after bowel resection for Crohn's disease (CD).

MATERIALS AND METHODS

We analyzed 88 adults (60 males and 28 females; mean age, 31.4 ± 9.6 years) who underwent bowel surgery for CD that created ileocolic anastomosis without enteric stoma, and underwent CTE for surveillance of CD recurrence/aggravation within 12 post-operative months. The CD activity index (CDAI) at the time of CTE was < 150 (i.e., clinically silent) in 51 patients, and ≥ 150 in 37 patients. Diagnostic yields of CTE regarding CD recurrence in the ileocolic anastomosis and extraluminal penetrating complications were determined. CTE-related step-up therapy was recorded. These outcomes were compared between the two CDAI groups after accounting for major risk factors for CD recurrence. In a subgroup of 31 patients who underwent both CTE and ileocolonoscopy within 1 month, CTE accuracy for anastomotic recurrence was assessed using the Rutgeerts scoring as the reference standard.

RESULTS

CTE diagnostic yield was 35.2% (31/88) for the anastomotic recurrence and 9.1% (8/88) for penetrating complications. 20.5% (18/88) of the patients underwent step-up therapy after CTE detection of anastomotic recurrence. These outcomes were not significantly different between CDAI < 150 and CDAI ≥ 150, except that CTE yield for extraluminal penetrating complications was significantly higher in CDAI ≥ 150 (16.2% [6/37] vs. 3.9% [2/51]; multivariable-adjusted p = 0.029). CTE showed 92.3% (12/13) sensitivity and 83.3% (15/18) specificity for anastomotic recurrence.

CONCLUSION

CTE may be a viable option for the early postsurgical surveillance of recurred disease in CD patients.

Magnetic resonance index of activity (MaRIA) and Clermont score are highly and equally effective MRI indices in detecting mucosal healing in Crohn's disease

BACKGROUND

Magnetic resonance index of activity (MaRIA) and Clermont score are currently the two main MRI indices that have been validated compared to endoscopy in Crohn's disease (CD).

AIMS

To compare the accuracy of MaRIA and Clermont score in assessing CD mucosal healing.

METHODS

Fourty-four CD patients underwent prospectively and consecutively MRI and colonoscopy.

RESULTS

Considering 207 segments, MaRIA>7 and Clermont score>8.4 demonstrated substantial accuracy to detect endoscopic ulcerations (73.9% and 74.0%, respectively) and presented with high specificity (82.1% and 81.3%) and high negative predictive value (NPV) (82.1% and 82.4%) for MaRIA and Clermont score, respectively. The sensitivity for detecting deep ulcerations was 90.9% for both MaRIA>11 and Clermont score>12.5, with a specificity of 82.0% and 80.0%, respectively. Among 44 patients, deep MRI remission predicted mucosal healing with specificity=85.3% and NPV=85.3% according to Barcelona criteria (no segmental MaRIA>7), and specificity=88.2% and NPV=85.7% according to Clermont criteria (no segmental Clermont score>8.4). In addition, MRI remission predicted mucosal healing with specificity=76.5% and NPV=86.7% according to Barcelona criteria (no segmental MaRIA>11), and specificity=79.4% and NPV=84.4% according to Clermont criteria (no segmental Clermont score>12.5).

CONCLUSION

MaRIA and Clermont score are equally effective in detecting CD endoscopic ulcerations supporting their use as therapeutic endpoints.