Evaluation of Quantitative PET/MR Enterography Biomarkers for Discrimination of Inflammatory Strictures from Fibrotic Strictures in Crohn Disease

Histopathology Scoring Systems of Stenosis Associated With Small Bowel Crohn's Disease: A Systematic Review

BACKGROUND & AIMS

Stenosis is a common complication of Crohn's disease (CD) that has no effective medical therapy. Development of antifibrotic agents will require testing in randomized controlled trials. Computed tomography enterography- and magnetic resonance enterography-based technologies might be used to measure outcomes in these trials. These approaches have been validated in studies of patients with symptomatic strictures who underwent imaging evaluations followed by resection with histopathologic grading of the intestinal tissue for inflammation and/or fibrosis (the reference standard). Imaging findings have correlated with findings from quantitative or semiquantitative histologic evaluation of the degree of fibromuscular stenosis and/or inflammation on the resection specimen. However, it is not clear whether histologic findings are an accurate reference standard. We performed a systematic review of all published histologic scoring systems used to assess stenosing CD.

METHODS

We performed a comprehensive search of Embase and MEDLINE of studies through March 13, 2019, that used a histologic scoring system to characterize small bowel CD and assessed inflammatory and fibrotic alterations within the same adult individual. All scores fitting the criteria were included in our analysis, independent of the presence of stricturing disease, as long as inflammation and fibrosis were evaluated separately but in the same scoring system.

RESULTS

We observed substantial heterogeneity among the scoring systems, which were not derived from modern principles for evaluative index development. None had undergone formal validity or reliability testing. None of the existing indices had been constructed according to accepted methods for the development of evaluative indices. Basic knowledge regarding their operating properties were lacking. Specific indices for evaluating the important pathologic component of myofibroblast hypertrophy or hyperplasia have not been proposed.

CONCLUSIONS

In a systematic review of publications, we found a lack of validated histopathologic scoring systems for assessment of fibromuscular stenosis. Data that describe the operating properties of existing cross-sectional imaging techniques for stenosing CD should be questioned. Development and validation of a histopathology index is an important research priority.

A novel collagen area fraction index to quantitatively assess bowel fibrosis in patients with Crohn's disease

BACKGROUND

A validated histopathological tool to precisely evaluate bowel fibrosis in patients with Crohn's disease is lacking. We attempted to establish a new index to quantify the severity of bowel fibrosis in patients with Crohn's disease-associated fibrostenosis.

METHODS

We analyzed the histopathological data of 31 patients with Crohn's disease strictures undergoing surgical resection. The most representative sections of resected strictured segments were stained with Masson trichrome to manifest bowel fibrosis. The collagen area fraction and histological fibrosis score were simultaneously calculated for the same section to evaluate the severity of bowel fibrosis.

RESULTS

Collagen area fraction strongly correlated with histological fibrosis scores (r = 0.733, P < 0.001). It showed a stronger correlation (r = 0.561, P < 0.001) with the degree of bowel strictures than the histological fibrosis score did (r = 0.468, P < 0.001). It was also shown to be more accurate for diagnosing Crohn's disease strictures (area under the receiver operating characteristic curve = 0.815, P < 0.001) compared with the histological fibrosis score (area under the curve = 0.771, P < 0.001). High repeatability was observed for the collagen area fraction, with an intraclass correlation coefficient of 0.915 (P < 0.001).

CONCLUSIONS

Collagen area fraction is a simple and reliable index to quantify the severity of bowel fibrosis in patients with Crohn's disease-associated fibrostenosis.

Texture Analysis of Magnetic Resonance Enterography Contrast Enhancement Can Detect Fibrosis in Crohn Disease Strictures

OBJECTIVE

The aim of the study was to investigate if texture analysis of contrast-enhanced magnetic resonance enterography (MRE) images can determine Crohn disease (CD) stricture histologic type.

MATERIALS AND METHODS

A radiology report database query identified 25 pediatric patients with established CD who underwent MRE followed by bowel resection within 30 days. MRE images were reviewed to identify strictures on enteric phase T1-weighted fat-suppressed images, that were matched with sites of histologic sectioning. Regions of interest were drawn over the bowel wall and texture analysis was performed using TexRAD software (Cambridge, UK), with skewness, mean, entropy and standard deviation parameters assessed. A pathologist reviewed all stricture histology specimens to assess for active mucosal inflammation and mural fibrosis. Multivariate logistic regression and analysis of variance were performed to identify texture features associated with stricture fibrosis.

RESULTS

Sixty-four bowel segments from 25 patients (mean age 16 ± 2 years) with imaging-histologic correlation were included. Of note, all strictures included had undergone surgical resection with MRE imaging available within 30 days. The histologic distribution of these bowel segments included 9 segments that showed active inflammation without fibrosis, 23 segments that showed only fibrosis, and 32 mixed segments with concomitant active inflammation and fibrosis. Bivariate regression analysis demonstrated that skewness, standard deviation, entropy, and mean texture analysis features are independently associated with stricture fibrosis. Stepwise logistic regression showed that the combination of mean, skewness, and entropy texture predicted stricture fibrosis with a goodness-of-fit value of 0.995. A combination of threshold values for these 3 texture analysis parameters was able to correctly classify 100% of the strictures in the study cohort for presence (55/55) and absence (9/9) of fibrosis.

CONCLUSIONS

MRE texture analysis (MRE-TA) texture features can differentiate CD stricture types and accurately detect fibrosis.

Noninvasive Multimodal Methods to Differentiate Inflamed vs Fibrotic Strictures in Patients With Crohn's Disease

Fibrotic strictures occur in 30% of patients with Crohn's disease (CD). However, there are no therapeutic agents that prevent or reverse fibrotic strictures. Strictures are treated by endoscopic dilatation procedures and surgical procedures, but there are high rates of recurrence. Two antifibrotic agents (nintedanib and pirfenidone) recently were approved for the treatment of idiopathic pulmonary fibrosis and inhibitors of Rho-associated protein kinases 1 and 2 reversed fibrosis in mice with chronic intestinal inflammation. Cross-sectional imaging techniques, such as magnetic resonance (MR) enterography, computed tomography enterography, and bowel ultrasound, are used to assess small-bowel and CD-related complications, including strictures. It is important to be able to determine the degree of inflammation and fibrosis in strictures to select the best therapy; this can be a challenge because inflammation and fibrosis co-exist to varying degrees in a damaged bowel segment. Delayed gadolinium enhancement, magnetization transfer MR imaging, and ultrasound elastography seem to be promising tools for assessing fibrosis in patients with CD. We review noninvasive techniques for fibrosis assessment, including analyses of genetic, epigenetic, and protein markers. We discuss the potential of imaging techniques such as diffusion-weighted and magnetization transfer MR imaging, strain elastography, shear-wave imaging, and positron emission tomography to guide therapeutic decisions for patients with stricturing CD.

The Role of the Radiologist in Determining Disease Severity in Inflammatory Bowel Diseases

Crohn's disease and ulcerative colitis are chronic inflammatory diseases that lead to progressive bowel damage including the development of stricturing and penetrating complications. Increasingly, cross-sectional imaging with computed tomography or magnetic resonance scans have emerged as leading tools to: (1) assess disease activity; (2) monitor response to therapy or disease recurrence; and (3) identify disease-related complications. Several validated radiological scoring systems have been developed to quantify cross-sectional and longitudinal inflammatory burden in these diseases and to monitor response to treatment. Bowel ultrasound is also a simple and inexpensive tool but is operator dependent in its performance.

Imaging fibrosis in inflammatory diseases: targeting the exposed extracellular matrix

In a variety of diseases, from benign to life-threatening ones, inflammation plays a major role. Monitoring the intensity and extent of a multifaceted inflammatory process has become a cornerstone in diagnostics and therapy monitoring. However, the current tools lack the ability to provide insight into one of its most crucial aspects, namely, the alteration of the extracellular matrix (ECM). Using a radiolabeled platelet glycoprotein VI-based ECM-targeting fusion protein (GPVI-Fc), we investigated how binding of GPVI-Fc on fibrous tissue could uncover the progression of several inflammatory disease models at different stages (rheumatoid arthritis, cutaneous delayed-type hypersensitivity, lung inflammation and experimental autoimmune encephalomyelitis). Methods: The fusion protein GPVI-Fc was covalently linked to 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and subsequently labeled with 64Cu. We analyzed noninvasively in vivo64Cu-GPVI-Fc accumulation in murine cutaneous delayed-type hypersensitivity, anti-glucose-6-phosphate isomerase serum-induced rheumatoid arthritis, lipopolysaccharide-induced lung inflammation and an experimental autoimmune encephalomyelitis model. Static and dynamic Positron Emission Tomography (PET) of the radiotracer distribution was performed in vivo, with ex vivo autoradiography confirmation, yielding quantitative accumulation and a distribution map of 64Cu-GPVI-Fc. Ex vivo tissue histological staining was performed on harvested samples to highlight the fusion protein binding to collagen I, II and III, fibronectin and fibrinogen as well as the morphology of excised tissue. Results:64Cu-GPVI-Fc showed a several-fold increased uptake in inflamed tissue compared to control tissue, particularly in the RA model, with a peak 24 h after radiotracer injection of up to half the injected dose. Blocking and isotype control experiments indicated a target-driven accumulation of the radiotracer in the case of chronic inflammation. Histological analysis confirmed a prolonged accumulation at the inflammation site, with a pronounced colocalization with the different components of the ECM (collagen III and fibronectin notably). Binding of the fusion protein appeared to be specific to the ECM but unspecific to particular components. Conclusion: Imaging of 64Cu-GPVI-Fc accumulation in the ECM matrix appears to be a promising candidate for monitoring chronic inflammation. By binding to exposed fibrous tissue (collagen, fibronectin, etc.) after extravasation, a new insight is provided into the fibrotic events resulting from a prolonged inflammatory state.

Novel Imaging Approaches in Inflammatory Bowel Diseases

Inflammatory bowel diseases are chronic autoimmune conditions of the gastrointestinal tract, mainly grouped into ulcerative colitis or Crohn's disease. Traditionally, symptoms have been used to guide IBD management, but this approach is fatally flawed, as symptoms don't correlate with disease activity and often fail to predict disease complications, especially with Crohn's disease. Hence, there is increasing recognition of the need for treatment algorithms based on objective measures of bowel inflammation. In this review, we will focus on advancements in the endoscopic and radiological imaging armamentarium that allow detailed assessments from intestinal mucosa to mesentery.

Assessment of Ileocolonic Inflammation in Crohn's Disease: Which Surrogate Marker Is Better-MaRIA, Clermont, or PET/MR Index? Initial Results of a Feasibility Trial

Our objective was to define an ¹⁸F-FDG PET/MR enterography index as a hybrid surrogate marker for active ileocolonic inflammation in Crohn's disease (CD) and assess its diagnostic performance in comparison to validated MR indices (MR index of activity [MaRIA], Clermont score). Methods: Fifty-two CD patients with recurrent symptoms underwent ileocolonoscopy and ¹⁸F-FDG PET/MR enterography. Three hundred three ileocolonic segments were assessed for inflammation using MaRIA and the Clermont score as well as the newly defined PET/MR index. On the basis of tobit regression, the PET/MR index was defined as (0.87 × wall thickness) + (1.97 × edema) + (0.83 × ulceration) + (0.55 × SUVmax ratio) + 1.14. The endoscopic activity of inflammation was determined by the simplified endoscopic activity score for CD (SES-CD). Receiver-operating-characteristic curves for each surrogate marker were created and tested against each other using the DeLong test, and diagnostic accuracies were compared using the McNemar test. Correlations between surrogate markers and SES-CD were tested with the Spearman rank correlation test. Results: The PET/MR index showed a comparable sensitivity but a significantly higher specificity and accuracy than MaRIA and the Clermont score in predicting both active and severe inflammation (active inflammation: specificities of 0.933, 0.711, and 0.707 and accuracies of 0.921, 0.739, and 0.736, P < 0.001; severe inflammation: specificities of 0.91, 0.81, and 0.785 and accuracies of 0.914, 0.818, and 0.795, P < 0.01, respectively). All surrogate markers correlated moderately with SES-CD on a segmental basis and a global level (0.5 < ρ < 0.7, all P < 0.001). Conclusion: As a hybrid surrogate marker comprising MR parameters and the PET component, the PET/MR index yielded significantly improved specificity and diagnostic accuracy compared with conventional MR indices (MaRIA and the Clermont score), demonstrating its high potential for noninvasive assessment of CD.

PET/MRI in Infection and Inflammation

Hybrid positron emission tomography/magnetic resonance imaging (PET/MR) systems are now more and more available for clinical use. PET/MR combines the unique features of MR including excellent soft tissue contrast, diffusion-weighted imaging, dynamic contrast-enhanced imaging, fMRI and other specialized sequences as well as MR spectroscopy with the quantitative physiologic information that is provided by PET. Most of the evidence of the potential clinical utility of PET/MRI is available for neuroimaging. Other areas, where PET/MR can play a larger role include head and neck, upper abdominal, and pelvic tumours. Although the role of PET/MR in infection and inflammation of the cardiovascular system and in musculoskeletal applications are promising, these areas of clinical investigation are still in the early phase and it may be a little longer before these areas reach their full potential in clinical practice. In this review, we outline the potential of hybrid PET/MR for imaging infection and inflammation. A background to the main radiopharmaceuticals and some technical considerations are also included.

Lower Gastrointestinal Tract Applications of PET/Computed Tomography and PET/MR Imaging

This article discusses the role of PET/CT and PET/MR imaging in the evaluation of inflammatory and malignant disorders of the lower gastrointestinal tract. This includes a review of the current literature and a discussion of new and emerging research.

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.

Clinical PET/MRI: 2018 Update

OBJECTIVE

The purpose of this article is to provide an update on clinical PET/MRI, including current and developing clinical indications and technical developments.

CONCLUSION

PET/MRI is evolving rapidly, transitioning from a predominant research focus to exciting clinical practice. Key technical obstacles have been overcome, and further technical advances promise to herald significant advancements in image quality. Further optimization of protocols to address challenges posed by this hybrid modality will ensure the long-term success of PET/MRI.

Noninvasive Biomarkers of Colorectal Cancer: Role in Diagnosis and Personalised Treatment Perspectives

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths worldwide. It has been estimated that more than one-third of patients are diagnosed when CRC has already spread to the lymph nodes. One out of five patients is diagnosed with metastatic CRC. The stage of diagnosis influences treatment outcome and survival. Notwithstanding the recent advances in multidisciplinary management and treatment of CRC, patients are still reluctant to undergo screening tests because of the associated invasiveness and discomfort (e.g., colonoscopy with biopsies). Moreover, the serological markers currently used for diagnosis are not reliable and, even if they were useful to detect disease recurrence after treatment, they are not always detected in patients with CRC (e.g., CEA). Recently, translational research in CRC has produced a wide spectrum of potential biomarkers that could be useful for diagnosis, treatment, and follow-up of these patients. The aim of this review is to provide an overview of the newer noninvasive or minimally invasive biomarkers of CRC. Here, we discuss imaging and biomolecular diagnostics ranging from their potential usefulness to obtain early and less-invasive diagnosis to their potential implementation in the development of a bespoke treatment of CRC.

Magnetic Resonance Imaging Predicts Histopathological Composition of Ileal Crohn's Disease

BACKGROUND AND AIMS

Recently, smooth muscle hypertrophy has been suggested to be a contributor to small bowel lesions secondary to Crohn's disease [CD], in addition to inflammation and fibrosis. Here, we assess the value of magnetic resonance imaging [MRI] for the characterisation of histopathological tissue composition of small bowel CD, including inflammation, fibrosis, and smooth muscle hypertrophy.

METHODS

A total of 35 consecutive patients [male/female 17/18, mean age 33 years] with ileal CD, who underwent small bowel resection and a preoperative contrast-enhanced MRI examination within 1 month before surgery, were retrospectively included. Image assessment included qualitative [pattern/degree of enhancement, presence of ulcerations/fistulas/abscesses] and quantitative parameters [wall thickness on T2/T1-weighted images [WI], enhancement ratios, apparent diffusion coefficient [ADC], Clermont and Magnetic Resonance Index of Activity [MaRIA] scores). MRI parameters were compared with histopathological findings including active inflammation, collagen deposition, and muscle hypertrophy using chi square/Fisher or Mann-Whitney tests and univariate/multivariate logistic/linear regression analyses.

RESULTS

Forty ileal segments were analysed in 35 patients. Layered pattern at early-post-contrast phase was more prevalent (odds ratio [OR] = 8; p = 0.008), ADC was significantly lower [OR = 0.005; p = 0.022], and MaRIA score was significantly higher [OR = 1.125; p = 0.022] in inflammation grades 2-3 compared with grade 1. Wall thickness on T2WI was significantly increased [OR = 1.688; p = 0.043], and fistulas [OR = 14.5; p = 0.017] were more prevalent in segments with disproportionately increased muscle hypertrophy versus those with disproportionately increased fibrosis. MaRIA/Clermont scores, wall thickness on T1WI and T2WI, and ADC were all significantly correlated with degree of muscular hypertrophy.

CONCLUSIONS

MRI predicts the degree of inflammation, and can distinguish prominent muscle hypertrophy from prominent fibrosis in ileal CD with reasonable accuracy (area under receiver operating characteristic curve [AUROC] > 0.7).

Positron emission tomography/magnetic resonance imaging (PET/MRI): An update and initial experience at HC-FMUSP

The new technology of PET/MRI is a prototype of hybrid imaging, allowing for the combination of molecular data from PET scanning and morphofunctional information derived from MRI scanning. Recent advances regarding the technical aspects of this device, especially after the development of MRI-compatible silicon photomultipliers of PET, permitted an increase in the diagnostic performance of PET/MRI translated into dose reduction and higher imaging quality. Among several clinical applications, PET/MRI gains ground initially in oncology, where MRI per se plays an essential role in the assessment of primary tumors (which is limited in the case of PET/CT), including prostate, rectal and gynecological tumors. On the other hand, the evaluation of the lungs remains an enigma although new MRI sequences are being designed to overcome this. More clinical indications of PET/MRI are seen in the fields of neurology, cardiology and inflammatory processes, and the use of PET/MRI also opens perspectives for pediatric populations as it involves very low radiation exposure. Our review aimed to highlight the current indications of PET/MRI and discuss the challenges and perspectives of PET/MRI at HC-FMUSP.

T2* Mapping to characterize intestinal fibrosis in crohn's disease

BACKGROUND

Assessing bowel fibrosis in patients with Crohn's disease (CD) has important therapeutic implications.

PURPOSE

To determine the utility of T2* mapping versus that of contrast enhanced (CE) imaging in grading intestinal fibrosis in patients with CD using surgical pathology as the reference standard.

STUDY TYPE

Prospective.

SPECIMENS

102 specimens from 27 patients with CD.

FIELD STRENGTH/SEQUENCE

3.0T; T2WI; T1WI; T2*WI.

ASSESSMENT

The T2*WI values of the bowel wall targeted for resection were measured by two radiologists by drawing regions of interest on the thickened bowel wall. The resected bowel specimens with pathological fibrosis and type I collagen were classified into four severity grades (0-3) by a pathologist using a semi-quantitative scoring system.

STATISTICAL TESTS

The differences in the T2*WI values among the different histological grades were analyzed using one-way analysis of variance or the Kruskal-Wallis test, and their correlations were analyzed. The ability of the T2*WI values to discriminate between various degrees of fibrosis was assessed using a receiver operating characteristic (ROC) curve.

RESULTS

Significant differences were observed in the T2* values of mild (23.56 ± 1.60 ms), moderate (16.19 ± 0.55 ms), and severe (13.59 ± 0.53 ms) fibrosis types (F = 35.84; P < 0.001). T2* values were moderately associated with histological fibrosis (r = -0.627; P < 0.001) and type I collagen scores (r = -0.588; P < 0.001). T2* values were highly accurate, with an area under the ROC curve (AUC) of 0.951 (P < 0.001) for differentiating moderate-to-severe fibrosis from nonfibrosis and mild fibrosis, followed by an AUC of 0.508 for the percentage of enhancement gain (P = 0.908). A threshold T2* value of 18.06 ms was recommended for diagnosing moderate-to-severe fibrosis with 94.7% sensitivity and 78.3% specificity.

DATA CONCLUSION

MRI T2* mapping outperforms CE parameters in distinction of various degrees of bowel fibrosis in CD.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.

Differentiation of Inflammatory From Fibrotic Ileal Strictures among Patients with Crohn's Disease Based on Visual Analysis: Feasibility Study Combining Conventional B-Mode Ultrasound, Contrast-Enhanced Ultrasound and Strain Elastography

The aim of this pilot study was to assess prospectively the feasibility of conventional B-mode ultrasound (US) and contrast-enhanced ultrasound (CEUS) combined with real-time strain elastography (SE) in the differentiation of inflammatory from fibrotic ileal strictures among patients with Crohn's disease (CD) based on visual analysis. Twenty non-consecutive patients (15 male and 5 female; mean age ± standard deviation, 40.2 ± 10.22 y) with CD and stricture of the terminal ileal loop were scanned by conventional B-mode US and CEUS and, subsequently, by real-time SE. Two independent readers visually classified each bowel stricture as fibrotic or inflammatory based on conventional B-mode US, CEUS, SE, individually and then for all techniques combined. All techniques combined had a higher (p <0.05) sensitivity (reader 1, 9/20 [45%]; reader 2, 7/20 [35%]), specificity (reader 1, 5/20 [25%]; reader 2, 8/20 [40%]) and diagnostic accuracy (reader 1, 14/20 [70%]; reader 2, 15/20 [75%]) and higher (p <0.05) area under the receiver operating characteristic curve (reader 1, 0.953; reader 2, 0.921) than individual techniques. Inter-reader agreement was fair for conventional B-mode US (k = 0.46) and CEUS (k = 0.39), moderate for SE (k = 0.6) and fair for all techniques combined (k = 0.38). Conventional B-mode US and CEUS, in combination with SE, may improve differentiation of inflammatory from fibrotic ileal strictures among patients with CD based on visual analysis.

Characterization of Degree of Intestinal Fibrosis in Patients with Crohn Disease by Using Magnetization Transfer MR Imaging

Purpose To evaluate the role of magnetization transfer (MT) magnetic resonance (MR) imaging for the characterization of intestinal fibrosis compared with contrast material-enhanced and diffusion-weighted MR imaging and its capability for differentiating fibrotic from inflammatory strictures in humans with Crohn disease (CD) by using surgical histopathologic analysis as the reference standard. Materials and Methods Institutional review board approval and informed consent were obtained for this prospective study. Abdominal MT imaging, contrast-enhanced imaging, and diffusion-weighted imaging of 31 consecutive patients with CD were analyzed before elective surgery. The bowel wall MT ratio normalized to skeletal muscle, the apparent diffusion coefficient (ADC), and the percentage of enhancement gain were calculated; region-by-region correlations with the surgical specimen were performed to determine the histologic degree of fibrosis and inflammation. The performance of MT imaging was validated in five new patients. One-way analysis of variance test, Spearman rank correlation, and receiver operating characteristic curve were used for statistical analysis. Results Normalized MT ratios strongly correlated with fibrosis scores (r = 0.769; P = .000) but did not correlate with inflammation scores (r = -0.034; P = .740). Significant differences (F = 49.002; P = .000) in normalized MT ratios were found among nonfibrotic, mildly, moderately, and severely fibrotic walls. The normalized MT ratios of mixed fibrotic and inflammatory bowel walls were significantly higher than those of bowel walls with only inflammation present (t = -8.52; P = .000). A high accuracy of normalized MT ratios was shown with an area under the receiver operating characteristic curve (AUC) of 0.919 (P = .000) for differentiating moderately to severely fibrotic bowel walls from nonfibrotic and mildly fibrotic bowel walls, followed by ADC (AUC, 0.747; P = .001) and the percentage of enhancement gain (AUC, 0.592; P = .209). The sensitivity, specificity, and AUC of MT imaging for diagnosing moderate to severe fibrosis in the validation data set were 80% (12 of 15), 100% (three of three), and 0.9 (P = .033), respectively. Conclusion MT imaging outperforms ADC and contrast-enhanced imaging in detecting and distinguishing varying degrees of bowel fibrosis with or without coexisting inflammation. MT imaging could potentially be used as a method to differentiate fibrotic from inflammatory intestinal strictures in patients with CD. ^© RSNA, 2018 Online supplemental material is available for this article.

Differentiation of Inflammatory from Fibrotic Ileal Strictures among Patients with Crohn's Disease through Analysis of Time-Intensity Curves Obtained after Microbubble Contrast Agent Injection

The aim of the study described here was to assess whether the analysis of time-intensity curves obtained after microbubble contrast agent injection could differentiate inflammatory from fibrotic ileal strictures among patients with Crohn's disease. Sixty-five consecutive patients (40 male and 25 female; mean age ± SD, 42.2 ± 12.22 y) with stricture of the terminal ileal loop from Crohn's disease were scanned after microbubble injection. Time-intensity curves were obtained from quantitative analysis, and peak enhancement, rise time, time to peak, area under the time-intensity curve (AUC), AUC during wash-in (AUCWI) and AUC during wash-out (AUCWO) were compared between patients with inflammatory strictures and patients with fibrotic strictures. Inflammatory (n = 40) and fibrotic (n = 25) strictures differed (p < 0.05) in peak enhancement, wash-in rate, wash-in perfusion index, AUC, AUCWI and AUCWO. The quantitative analysis of small bowel wall contrast enhancement after microbubble contrast agent injection may differentiate inflammatory from fibrotic ileal strictures in patients with Crohn's disease.

MR Enterography Assessment of Bowel Inflammation Severity in Crohn Disease Using the MR Index of Activity Score: Modifying Roles of DWI and Effects of Contrast Phases

OBJECTIVE

The purpose of this article is to appraise the use of the MR index of activity (MaRIA) score in evaluating Crohn disease (CD) on present-day MR enterography images, with an emphasis on determining the modifying roles of DWI and the effects of different contrast enhancement phases.

SUBJECTS AND METHODS

Fifty patients prospectively underwent MR enterography, including DWI and enteric and portal phase scans, and ileocolonoscopy with segmental CD endoscopic index of severity (CDEIS) scoring within a week. Thirty-nine terminal ilea and 40 right-sided colons (mean [± SD] segmental CDEIS score, 14.3 ± 12.1) from 42 patients with CD (mean age, 27 ± 6.2 years) were finally analyzed by three independent readers. Original and modified (ulcer replaced with DWI grade) MaRIA scores were compared regarding their correlation with segmental CDEIS score, accuracy in diagnosing active (segmental CDEIS score ≥ 3) and severe (segmental CDEIS score ≥ 12) inflammation, and interobserver reproducibility. The primary analysis used portal phase data, and the agreement between portal and enteric phase scores was analyzed.

RESULTS

MaRIA and modified MaRIA scores correlated similarly with CDEIS scores (r = 0.737 and 0.742; p = 0.387) and did not significantly differ in terms of AUC values for the diagnosis of active (0.909 and 0.903; p = 0.571) or severe (0.907 and 0.892; p = 0.443) inflammation. The intraclass correlation coefficient was significantly higher for modified MaRIA than for MaRIA (0.845 and 0.701; p < 0.001). The mean difference between portal and enteric phase scores (i.e., portal minus enteric) was 0.33-0.36 score points for individual readers, and the Bland-Altman repeatability coefficient was 0.9-1.42 score points.

CONCLUSION

Interobserver reproducibility in evaluating the severity of bowel inflammation in CD using the MaRIA score can be improved by modification with DWI. MaRIA scoring provides steady results across enteric and portal phases.

Nuclear Medicine Imaging in Pediatric Infection or Chronic Inflammatory Diseases

In this review article, we focus on the most recent applications of nuclear medicine techniques (mainly ^99mTc/¹¹¹In white blood cells (WBC) scan, [¹⁸F]-FDG-PET/CT, [¹⁸F]-FDG-PET/MRI, and ^99mTc-IL-2 scintigraphy) in the study of children affected by peripheral bone osteomyelitis, fungal infections, inflammatory bowel diseases, and type 1 diabetes, owing to recent important published evidences of their role in the management of these diseases. For osteomyelitis in children, both bone scintigraphy and [¹⁸F]-FDG-PET have a major advantage of assessing the whole body in one imaging session to confirm or exclude multifocal involvement, whereas WBC scan has a limited role. In children with fungal infections, [¹⁸F]-FDG-PET can help in defining the best location for biopsy and can help in evaluating the extent of the infection and organs involved (also sites that were not yet clinically apparent), although its main role is for therapy monitoring. In inflammatory bowel diseases, and Crohn disease in particular, WBC scan has been successfully used for many years, but it is now used only in case of doubtful magnetic resonance (MR) or when MR cannot be performed and endoscopy is inconclusive. By contrast, there is an accumulating evidence of the role of [¹⁸F]-FDG-PET in management of children with Crohn disease, and PET/MR could be a versatile and innovative hybrid imaging technique that combines the metabolic information of PET with the high soft tissue resolution of MR, particularly for distinguishing fibrotic from active strictures. Finally, there are several new radiopharmaceuticals that specifically target inflammatory cells involved in the pathogenesis of insulitis aiming at developing new specific immunotherapies and to select children candidates to these treatments for improving their quality of life.

An overview of PET/MR, focused on clinical applications

Hybrid PET/MR scanners are innovative imaging devices that simultaneously or sequentially acquire and fuse anatomical and functional data from magnetic resonance (MR) with metabolic information from positron emission tomography (PET) (Delso et al. in J Nucl Med 52:1914-1922, 2011; Zaidi et al. in Phys Med Biol 56:3091-3106, 2011). Hybrid PET/MR scanners have the potential to greatly impact not only on medical research but also, and more importantly, on patient management. Although their clinical applications are still under investigation, the increased worldwide availability of PET/MR scanners, and the growing published literature are important determinants in their rising utilization for primarily clinical applications. In this manuscript, we provide a summary of the physical features of PET/MR, including its limitations, which are most relevant to clinical PET/MR implementation and to interpretation. Thereafter, we discuss the most important current and emergent clinical applications of such hybrid technology in the abdomen and pelvis, both in the field of oncologic and non-oncologic imaging, and we provide, when possible, a comparison with clinically consolidated imaging techniques, like for example PET/CT.

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.

Small Bowel Imaging: Computed Tomography Enterography, Magnetic Resonance Enterography, Angiography, and Nuclear Medicine

Radiology examinations play a major role in the diagnosis, management, and surveillance of small bowel diseases and are complementary to endoscopic techniques. Computed tomography enterography and magnetic resonance enterography are the cross-sectional imaging studies of choice for many small bowel diseases. Angiography still plays an important role for catheter-directed therapies. With the emergence of hybrid imaging techniques, radionuclide imaging has shown promise for the evaluation of small bowel bleeding and Crohn disease and may play a larger role in the future. This article reviews recent advances in technology, diagnosis, and therapeutic options for selected small bowel disorders.

Role of molecular imaging in the management of patients affected by inflammatory bowel disease: State-of-the-art

AIM

To present the current state-of-the art of molecular imaging in the management of patients affected by inflammatory bowel disease (IBD).

METHODS

A systematic review of the literature was performed in order to find important original articles on the role of molecular imaging in the management of patients affected by IBD. The search was updated until February 2016 and limited to articles in English.

RESULTS

Fifty-five original articles were included in this review, highlighting the role of single photon emission tomography and positron emission tomography.

CONCLUSION

To date, molecular imaging represents a useful tool to detect active disease in IBD. However, the available data need to be validated in prospective multicenter studies on larger patient samples.

Diffusion-weighted MR enterography for evaluating Crohn's disease: Effect of anti-peristaltic agent on the diagnosis of bowel inflammation

OBJECTIVES

To prospectively investigate how Buscopan affects the diagnosis of bowel inflammation by diffusion-weighted imaging MR enterography (DWI-MRE) in Crohn's disease (CD).

METHODS

Thirty CD patients without previous bowel surgery underwent DWI-MRE (b = 900 sec/mm²) before and after intravenous Buscopan. The 30 patients were randomly divided into two groups; using a crossover design, interpretations were made regarding the presence of restricted mural diffusion (i.e., bowel inflammation) in nine bowel segments in two separate reading sessions by two readers. The readers also judged restricted mural diffusion extent in each bowel segment on two side-by-side DWI-MRE images with a random right-to-left order. Ileocolonoscopy and conventional MRE interpreted by an expert panel were reference standards.

RESULTS

We analyzed 262 bowel segments. DWI-MRE without Buscopan significantly decreased sensitivity for both readers (58.8 % vs. 72.9 %, P = 0.046; 57.6 % vs. 85.9 %, P = 0.001) and did not significantly increase specificity (P = 0.085 and 0.396). Two readers noted that 28.6 % and 23.3 % of 262 bowel segments had greater diffusion restriction extent on DWI-MRE with Buscopan compared with DWI-MRE without Buscopan (P < 0.001) and 68.7 % and 74 %, respectively, had similar extent between them.

CONCLUSION

Omitting Buscopan caused a greater loss in sensitivity of DWI-MRE than false-positive reduction for diagnosing bowel inflammation in CD.

KEY POINTS

• Omitting Buscopan significantly decreases DWI-MRE sensitivity for diagnosing bowel inflammation in CD. • Increase in the corresponding DWI-MRE specificity by omitting Buscopan is less apparent. • DWI-MRE without Buscopan underestimates the extent of bowel inflammation in CD.

A review of endoscopic balloon dilatation techniques for treating Crohn's strictures: time to standardise therapy

Endoscopic balloon dilatation (EBD) is a recognised treatment for symptomatic Crohn's disease strictures. Over 3000 procedure are reported in the literature and yet the long term benefits are unclear. This is largely because of different populations, study designs, techniques, types of strictures, the outcome measures used and follow-up periods. Areas covered: We summarised the techniques reported in the literature based on a systematic review and key factors that may influence outcome: pre-intervention imaging, stricture length and type, balloon size in relation to intestinal lumen diameter, duration of dilatation, frequency of repeat dilatation and instructions on follow-up. Expert commentary: We noted that shorter, non-ulcerated and anastomotic strictures fare better and 2 mins dilatation duration was the commonest technique used without an increased risk of complications. The findings were translated into a standardised protocol and a management pathway to guide clinicians on the therapeutic strategy for Crohn's strictures. To resolve the uncertainty about long-term benefits, future studies should adopt a replicable standardised EBD technique, define degree of fibrosis to decide therapy accordingly, compare it to alternative interventions (strictureplasty or stents) within a randomised controlled trial and apply a validated outcome measure to include intestinal damage and quality of life.

Combined PET/MRI: from Status Quo to Status Go. Summary Report of the Fifth International Workshop on PET/MR Imaging; February 15-19, 2016; Tübingen, Germany

This article provides a collaborative perspective of the discussions and conclusions from the fifth international workshop of combined positron emission tomorgraphy (PET)/magnetic resonance imaging (MRI) that was held in Tübingen, Germany, from February 15 to 19, 2016. Specifically, we summarise the second part of the workshop made up of invited presentations from active researchers in the field of PET/MRI and associated fields augmented by round table discussions and dialogue boards with specific topics. This year, this included practical advice as to possible approaches to moving PET/MRI into clinical routine, the use of PET/MRI in brain receptor imaging, in assessing cardiovascular diseases, cancer, infection, and inflammatory diseases. To address perceived challenges still remaining to innovatively integrate PET and MRI system technologies, a dedicated round table session brought together key representatives from industry and academia who were engaged with either the conceptualisation or early adoption of hybrid PET/MRI systems. Discussions during the workshop highlighted that emerging unique applications of PET/MRI such as the ability to provide multi-parametric quantitative and visual information which will enable not only overall disease detection but also disease characterisation would eventually be regarded as compelling arguments for the adoption of PET/MR. However, as indicated by previous workshops, evidence in favour of this observation is only growing slowly, mainly due to the ongoing inability to pool data cohorts from independent trials as well as different systems and sites. The participants emphasised that moving from status quo to status go entails the need to adopt standardised imaging procedures and the readiness to act together prospectively across multiple PET/MRI sites and vendors.

Novel biomarkers of fibrosis in Crohn’s disease

Fibrosis represents a major challenge in Crohn’s disease (CD), and many CD patients will develop fibrotic strictures requiring treatment throughout their lifetime. There is no drug that can reverse intestinal fibrosis, and so endoscopic balloon dilatation and surgery are the only effective treatments. Since patients may need repeated treatments, it is important to obtain the diagnosis at an early stage before strictures become symptomatic with extensive fibrosis. Several markers of fibrosis have been proposed, but most need further validation. Biomarkers can be measured either in biological samples obtained from the serum or bowel of CD patients, or using imaging tools and tests. The ideal tool should be easily obtained, cost-effective, and reliable. Even more challenging is fibrosis occurring in ulcerative colitis. Despite the important burden of intestinal fibrosis, including its detrimental effect on outcomes and quality of life in CD patients, it has received less attention than fibrosis occurring in other organs. A common mechanism that acts via a specific signaling pathway could underlie both intestinal fibrosis and cancer. A comprehensive overview of recently introduced biomarkers of fibrosis in CD is presented, along with a discussion of the controversial areas remaining in this field.

Imaging of intestinal fibrosis: current challenges and future methods

Crohn's disease (CD) activity assessments are dominated by inflammatory changes without discrete measurement of the coexisting fibrotic contribution to total bowel damage. Intestinal fibrosis impacts the development of severe structural complications and the overall natural history of CD. Measuring intestinal fibrosis is challenging and existing methods of disease assessment are unable to reliably distinguish fibrosis from inflammation. Both the immediate clinical need to measure fibrosis for therapeutic decision-making and the near-future need for tools to assess pipeline anti-fibrotic medications highlight the demand for biomarkers of fibrosis in CD. Developing non-invasive technologies exploit changes in intestinal perfusion, mechanical properties, and macromolecular content to provide quantitative markers of fibrosis. In this review of existing and experimental technologies for imaging intestinal fibrosis, we discuss the expanding capabilities of quantitative MR and ultrasound imaging, encouraging developments in non-invasive elastography, and emerging novel methods including photoacoustic imaging.

Diffusion-weighted MRI in Crohn's disease: Current status and recommendations

Over the past years, technological improvements and refinements in magnetic resonance imaging (MRI) hardware have made high-quality diffusion-weighted imaging (DWI) routinely possible for the bowel. DWI is promising for the detection and characterization of lesions in Crohn's disease (CD) and has been advocated as an alternative to intravenous gadolinium-based contrast agents. Furthermore, quantification using the apparent diffusion coefficient may have value as a biomarker of CD activity and has shown promise. In this article we critically review the literature pertaining to the value of DWI in CD for detection, characterization, and quantification of disease activity and complications. Although the body of supportive evidence is growing, it is clear that well-designed, multicenter studies are required before the role of DWI in clinical practice can be fully established. J. Magn. Reson. Imaging 2016;44:1381-1396.

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.

Hormonal contraceptives and venous thromboembolism: Are inflammatory bowel disease patients at increased risk? A retrospective study on a prospective database

Recent studies showed an increased risk of venous thromboembolism (VTE) in patients receiving oral hormonal contraceptives. Inflammatory bowel diseases (IBD) often affect young patients and represent a pro-coagulant condition. This could result from active inflammation, but a potential role for genetic and molecular factors has been suggested. Hormonal contraceptives have also been associated with increased risk of VTE and the risk may be greater in IBD patients that already are in a pro-coagulant status, but no definitive data are available in this population. The purpose of our study was to seek for differences of the risk of VTE in IBD patients receiving hormonal contraceptives compared with controls.

This is a retrospective study. We interrogated a prospectively maintained database of IBD patients observed at our outpatient clinic between 2000 and 2014. All female patients managed conservatively, with no active disease, who were taking oral hormone contraceptives in the study period, were included. Patients observed for other-than-IBD conditions at our Unit and at the Unit of Gynaecology and Obstetrics, receiving contraceptives, served as controls (ratio 1:2). Patients with cancer, those receiving hormonal therapy, and those with known genetic predisposition to VTE were excluded.

We included 146 six IBD patients and 290 controls. One patient in each group developed VTE. Overall, the incidence of VTE associated with oral contraceptives was 0.5%. IBD was associated with increased risk of VTE (OR 1.9, 95% CI 0.12–32.12, p > 0.99). Active smokers since 10 years (17.2%) had higher risks of VTE (OR 8.6, 95% CI 1.16–19.25, p = 0.03).

Our data show that patients with IBD in remission are not at higher risk of VTE due to oral oestrogen-containing contraceptives compared with non-IBD controls. Smokers are at increased risk, irrespective of the baseline disease.

•

Contraceptives do not increase the risk of VTE in IBD patients in remission.

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Irrespective of baseline disease, smoking is associated with VTE.

•

IBD patients receiving contraceptives should be encouraged to quit smoking.