State of the Art MR Enterography Technique

A British Society of Gastrointestinal and Abdominal Radiology multi-centre audit of imaging investigations in inflammatory bowel disease

OBJECTIVES

To evaluate current UK practice for inflammatory bowel disease (IBD) imaging against recommendations from published international literature.

METHODS

A retrospective multi-centre audit was undertaken evaluating imaging modalities, protocols, and pathways used to investigate IBD both in outpatient and inpatient settings during January-December 2022. Reporting practices and training provisions were also recorded.

RESULTS

Forty-one centres contributed: 35 centres provided complete data, whereas 6 centres provided incomplete data. Magnetic resonance enterography (MRE) was the most common modality for small bowel imaging across UK centres, comprising 13 099/18 784 (69.7%) investigations. There was regional variability in other modalities used, with 5 centres performing 81% of all intestinal ultrasound and 3 centres performing 65% of all small bowel follow-through. Compared with outpatients, inpatients with suspected IBD were significantly more likely to be imaged with techniques imparting ionising radiation whether scanned either in-hours (p = 0.005) or out-of-hours (p < 0.001). Non-ionising radiation imaging modalities were significantly less available out-of-hours (p < 0.0001). Sequences included in MRE protocols were variable. Disparity in imaging follow-up for patients prescribed biologic therapies was observed.

CONCLUSIONS

Considerable variation in UK IBD imaging practice has been identified. Improvements must be made to reduce the regional inequality of patient access to different imaging modalities and decrease reliance on ionising radiation for inpatients. Further research to standardise and optimise imaging pathways should be undertaken to improve uniformity, with emphasis placed on training and education.

ADVANCES IN KNOWLEDGE

This multi-centre audit showed considerable IBD imaging practice variation between UK centres, particularly for imaging modalities used between inpatient and outpatient groups and in-hours versus out-of-hours.

Multimodality Imaging of Small Bowel Crohn Disease

Computed tomography enterography, magnetic resonance enterography, and bowel ultrasound are complementary tools central to diagnosing and monitoring Crohn disease. These modalities can identify active inflammation, penetrating, and stricturing disease. Crohn disease must be monitored frequently to guide therapy, and resolution of inflammation on imaging correlates directly with steroid-free clinical remission. While disease activity assessment is qualitative, newer quantitative techniques to assess active inflammation are emerging. These as well as other techniques, such as contrast-enhanced ultrasound (US) and US elastography, will offer new tools for future radiologists.

Small bowel imaging in Crohn’s disease with a special focus on obesity, pregnancy and postsurgical assessment

Crohn’s disease (CD) is an immune-mediated, multisystem inflammatory disorder characterised by discontinuous transmural, sometimes granulomatous, inflammation of the gastrointestinal tract. Although it can occur anywhere in the gastrointestinal tract, it has a 70% predilection for the terminal ileum. Ileocolonoscopy with biopsy remains the gold standard for initial diagnosis and assessment of CD activity but has several limitations, including invasiveness, risk of complications and cost. With a shifting focus towards treatment targets including transmural healing, non-invasive imaging modalities are being used increasingly to assess the small bowel, particularly the terminal ileum. CT enterography, magnetic resonance enterography and gastrointestinal ultrasound are widely used for small bowel imaging in clinical practice and have relatively good sensitivity and specificity. Obesity is a growing problem for patients with CD and is associated with limitations in medical imaging. Equally, cross-sectional imaging in pregnant and postsurgical patients with CD has its own challenges. In this article, we review small bowel imaging in CD with a special focus on obesity, pregnancy and postsurgical assessment.

Debunking myths in radiology: ending pre-contrast fasting

Radiology departments have traditionally observed fasting protocols for patients undergoing radiological studies with intravenous contrast. However, there is no scientific evidence to support these protocols. This practice has potentially harmful consequences, such as interruptions to long-term medication, dehydration, hypoglycaemia, test delays or anxiety, and has no benefits in terms of study interpretation or patient safety. Numerous studies now suggest the need to review these protocols, as reflected in the updated policies of our specialty's main societies, such as the ESUR (European Society of Urogenital Radiology) and the ACR (American College of Radiology). In this article, we review the available scientific evidence on this topic, and present our centre's experience of eliminating fasting prior to contrast-enhanced imaging studies.

Magnetic Resonance Neurography of the Lumbosacral Plexus

Pain and weakness in the low back, pelvis, and lower extremities are diagnostically challenging, and imaging can be an important step in the workup and management of these patients. Technical advances in magnetic resonance neurography (MRN) have significantly improved its utility for imaging the lumbosacral plexus (LSP). In this article, the authors review LSP anatomy and selected pathology examples. In addition, the authors will discuss technical considerations for MRN with specific points for the branch nerves off the plexus.

Multiparametric MRI for Staging of Bowel Inflammatory Activity in Crohn's Disease with MUSE-IVIM and DCE-MRI: A Preliminary Study

RATIONALE AND OBJECTIVES

To investigate if the combination of multishot diffusion imaging-based multiplexed sensitivity encoding intravoxel incoherent motion (MUSE-IVIM) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is feasible for staging Crohn's disease (CD) activity.

MATERIALS AND METHODS

A total of 65 CD patients were enrolled and analyzed in this retrospective study. The simplified endoscopic score for Crohn's disease (SES-CD) and magnetic resonance index of activity (MaRIA) were used as the reference. The MUSE-IVIM and DCE-MRI data were acquired at 3.0-T MRI scanner and processed by two radiologists. Three MUSE-IVIM parameters: fast apparent diffusion coefficient (ADCfast), slow apparent diffusion coefficient (ADCslow), and the fractional perfusion (Fraction of ADCfast), as well as four DCE-MRI parameters: volume transfer constant (Ktrans), rate constant (Kep), extravascular extracellular volume fraction (Ve), and plasma volume fraction (Vp) were generated. Intraclass correlation coefficient (ICC), non-parametric test (Kruskal-Wallis H and Mann-Whitney U), logistic regression, receiver operating characteristic analysis, Delong test, and Spearman's correlation test were performed.

RESULTS

According to SES-CD, 116 ileocolonic segments with CD lesions were identified as: inactive, mild, and moderate to severe. With multivariable logistic regression analysis, ADCfast (p < 0.001), Fraction of ADCfast (p = 0.005), Ktrans (p < 0.001) and Kep (p = 0.003) were identified as significant factors for differentiating among the three groups. Binary logistic analyses identified ADCfast (p = 0.001), Ktrans (p = 0.014), and Kep (p = 0.029) as independent predictors for the active status. The combination of ADCfast, Ktrans, and Kep performed better than MaRIA score (p = 0.028), for differentiating inactive and active status. MaRIA score was positively correlated with ADCfast (p < 0.001), Ktrans (p < 0.001), Kep (p < 0.001), and Ve (p = 0.001), however, negatively correlated with Fraction of ADCfast (p < 0.001).

CONCLUSION

The combination of MUSE-IVIM and DCE-MRI has been demonstrated to accurately stage inflammatory activity in CD.

Diffusion-weighted imaging in Crohn's disease

BACKGROUND

Diffusion-weighted MRI (DWI) is routinely used in abdominal imaging. In addition to neoplastic diseases, inflammatory changes can be delineated and diagnosed based on diffusion restriction in DWI. DWI is also increasingly used in the context of MRI of the small and large intestine.

OBJECTIVE

This article focuses on the technical aspects of DWI and its role in the diagnosis of Crohn's disease (CD) as well as in the grading of disease severity and in treatment monitoring.

MATERIALS AND METHODS

Guidelines, basic research papers, and review articles were analyzed.

RESULTS

Diffusion-weighted MRI is a specialized MRI technique that visualizes the diffusion of water molecules in biological tissues. In the context of MRI of the small and large intestine, DWI facilitates the diagnosis of inflammatory bowel disease and assessment of treatment response. DWI enables detection of not only intra- and transmural changes, but also extramural pathologies and complications. However, DWI also has its limitations and challenges.

CONCLUSION

This article provides a comprehensive overview of the use of DWI for diagnostic evaluation of bowel wall changes and extramural complications in the setting of CD. It also summarizes the relevant evidence available in the literature.

Small Bowel Imaging from Stepchild of Roentgenology to MR Enterography: Part I: Guidance in Performing and Observing Normal and Abnormal Imaging Findings

MRE has become a standard imaging test for evaluating patients with small bowel pathology, but the indications, interpretation of imaging findings, methodology, and appropriate use must be standardized and widely known. Several signs of small bowel damage in inflammatory and non-inflammatory small bowel pathology include strictures, abscess, inflammatory activity, sinus tract, wall edema, fistula, mucosal lesions, and mesentery fat hypertrophy, all of which are widely and accurately explained by MRE. MRE is a non-invasive modality that accurately assesses the intra-luminal, parietal, and extra-luminal small bowel. The differential MRE appearance allows us to distinguish between different small bowel pathologies, such as neoplastic and non-neoplastic small bowel diseases. The purpose of this paper is to present the MRE technique, as well as the interpretation of imaging findings, through the approach of a rigorous stepwise methodology.

Magnetic Resonance Enterography Reinvented: Exploring the Potential of a New Natural Beverage as an Alternative to Polyethylene Glycol Solution

The aim of the present study was to test a new oral contrast medium composed of natural components for the magnetic resonance (MR) imaging of small bowel diseases. Between January 2018 and June 2019, 35 patients affected by ileocolic Crohn’s disease (CD) were enrolled in the present study. Each patient underwent two sequential MR enterographies, first with the standard polyethylene glycol (PEG) water solution and, after 3 weeks, with the new natural beverage designed by our team. At the end of the administration of each oral contrast, a satisfaction survey was given to the patients to assess the palatability of both beverages. The intestinal distention and the quality of images were evaluated by two expert radiologists for both studies and the interreader agreement was calculated. According to the satisfaction questionnaire, 97.1% of patients expressed positive judgments regarding the natural beverage (71.4% very good and 25.7% good) whereas only 8.6% of them appreciated the PEG water solution (8.6% good) (p = 0.0001). The degree of intestinal distention was excellent and good in 97.1% of patients after the administration of PEG and in 94.3% of the patients after the administration of the natural beverage, without significant differences between the two products and with almost perfect (k = 0.821) and substantial (k = 0.754) inter-observer variability, respectively. No statistical differences were observed between the two expert radiologists regarding the evaluation of the imaging quality; in particular, they were considered good and excellent in 100% of patients after the administration of PEG water solution and in 97.2% of those who took the natural beverage, with substantial (k = 0.618) and almost perfect (k = 0.858) inter-observer variability, respectively. The new natural beverage demonstrated the same intestinal distension and excellent image quality compared to the synthetic standard oral contrast administered during MRE for small bowel diseases, proving to be a valid alternative with better palatability.

[Magnetic resonance enterography/enteroclysis : Technical aspects and indications]

BACKGROUND

Magnetic resonance enterography/enteroclysma (MRE) is an examination technique without ionizing radiation that allows assessment of bowel wall changes and extraluminal pathologies/complications such as in chronic inflammatory bowel diseases, among others.

OBJECTIVES

To discuss requirements for optimal MR imaging of the small bowel, technical basis of MRE and principles for the development and optimization of a MRE protocol, and clinical indications for this specific imaging technique.

MATERIALS AND METHODS

Guidelines, basic and review papers will be analyzed.

RESULTS

MRE enables the diagnosis of inflammatory bowel diseases and neoplasms and their evaluation during therapy. In addition to intra- and transmural changes, extramural pathologies and complications can also be detected. Standard sequences include steady-state free precession sequences, T2-weighted single-shot fast spin echo sequences, and three-dimensional (3D) T1-weighted gradient echo (GRE) sequences with fat saturation after contrast administration. Prior to image acquisition, optimal patient preparation and distension of the bowel using intraluminal contrast agents is necessary.

CONCLUSIONS

Careful patient preparation for MRE, understanding of optimal imaging technique, and appropriate clinical indications are essential to achieve high-quality images of the bowel for accurate assessment and diagnosis as well as therapy monitoring of small bowel disease.

Challenges and Strategies to Optimising the Quality of Small Bowel Magnetic Resonance Imaging in Crohn's Disease

Magnetic resonance enterography (MRE) is one of the most highly utilised tools in the assessment of patients with small bowel Crohn's disease (CD). As a non-invasive modality, it has both patient and procedure-related advantages over ileocolonoscopy which is the current gold standard for Crohn's disease activity assessment. MRE relies upon high-quality images to ensure accurate disease activity assessment; however, few studies have explored the impact of image quality on the accuracy of small bowel CD activity assessment. Bowel distension and motion artifacts are two key imaging parameters that impact the quality of images obtained through MRE. Multiple strategies have been employed to both minimise the effects of motion artifacts and improve bowel distension. This review discusses the definitions of bowel distension and motion artifacts within the literature with a particular focus on current strategies to improve bowel distension and limit motion artifacts in MRE.

Treat to transmural healing: how to incorporate intestinal ultrasound into the treatment of inflammatory bowel disease

Intestinal ultrasound (IUS) is emerging as a key tool to achieving the therapeutic target of transmural healing in inflammatory bowel disease (IBD). IUS is a non-invasive, radiation-free, imaging modality comparable to MRI, CT and ileocolonoscopy (IC). With the appropriate training and equipment, IUS can be an easily repeatable bedside test for IBD diagnosis and disease monitoring, including treatment response. Core to successful high quality IUS employment are appropriate training and expert techniques; however, the training pathway will not be explored in this review. Given the increasing shift towards objective assessment for tight disease control, gastroenterologist-led IUS should be incorporated into the armamentarium of imaging modalities alongside radiologists, to enhance our diagnostic and monitoring toolbox. This comprehensive review aims to outline the current literature around IUS and propose the placement of IUS in a treat-to-target algorithm in IBD. Ultimately, IUS facilitates timely management decisions to optimise patient care with potential to revolutionise patient outcomes, moving towards transmural healing as the holy grail of therapy in IBD.

A Review on Inflammatory Bowel Diseases: Recent Molecular Pathophysiology Advances

Inflammatory bowel diseases are considered immune disorders with a complex genetic architecture involving constantly changing endogenous and exogenous factors. The rapid evolution of genomic technologies and the emergence of newly discovered molecular actors are compelling the research community to reevaluate the knowledge and molecular processes. The human intestinal tract contains intestinal human microbiota consisting of commensal, pathogenic, and symbiotic strains leading to immune responses that can contribute and lead to both systemic and intestinal disorders including IBD. In this review, we attempted to highlight some updates of the new IBD features related to genomics, microbiota, new emerging therapies and some major established IBD risk factors.

MR Enterography in Crohn's Disease: Comparison of Contrast Imaging with Diffusion-weighted Imaging and a special Form of Color Coding

Purpose

We compared contrast-enhanced MR enterography with diffusion-weighted sequences to evaluate the validity of diffusion-weighted sequences for activity assessment in Crohnʼs disease compared to endoscopy. In addition, we investigated a new color-coded image post-processing technique in comparison with standard sequences and endoscopy.

Materials and Methods

Included were 197 MR enterographies (2015–2017) performed by using standardized examination protocols. The intestine was divided into 7 segments, which were compared separately. The accuracy of the MR examinations with regard to disease activity was validated using the Seo and MaRIA score and endoscopy findings. In addition, the image data were post-processed using a color-coded evaluation method (DCE tool on OsiriX).

Results

The comparison between contrast-enhanced and diffusion-weighted sequences showed a highly significant correlation for all bowel sections with a mean Spearman correlation coefficient of 0.876 (0.809–0.928). The color-coded image post-processing showed a sensitivity of 83.2 % and a specificity of 70.5 % in comparison with the MaRIA score. In comparison to endoscopy, a sensitivity of 81.3 % and a specificity of 70.5 %. In comparison with endoscopy, the MaRIA score showed a sensitivity of 80.2 % and a specificity of 84.0 % at a cut-off of 7. The visual score according to Seo showed a sensitivity of 85.7 % with a specificity of 77.0 % in the contrast-weighted examination and a sensitivity of 87.9 % and a specificity of 71.8 % for diffusion weighted images.

Conclusion

Diffusion-weighted sequences are as good as contrast-weighted sequences for assessing inflammatory activity in Crohnʼs disease. Contrast is often helpful for assessing complications, but this was not the purpose of this study. Visual imaging using color-coded data sets was similarly good at detecting inflammation.

Key points:

Citation Format

Simplified Magnetic Resonance Index of Activity Is Useful for Terminal Ileal but not Colonic Disease in Pediatric Crohn Disease

BACKGROUND

Ileocolonoscopy (IC) detects mucosal inflammation and magnetic resonance enterography (MRE) detects transmural inflammation in Crohn disease (CD). We aimed to evaluate the relationship between the simplified magnetic resonance index of activity (MARIAs) and measures of inflammation by IC in children with newly diagnosed CD.

METHODS

Retrospective review of 140 patients 6-18 years of age with CD who had baseline IC and MRE within 5 weeks of diagnosis. MARIAs was calculated for each intestinal segment (terminal ileum [TI], ascending colon, transverse colon, descending colon, sigmoid colon, rectum), defined as (1 × thickness > 3 mm) + (1 × edema) + (1 × fat stranding) + (2 × ulcers). Sensitivity and specificity were derived using receiver operating characteristic (ROC) curves to compare MARIAs to IC findings.

RESULTS

Using IC as the reference standard, the cutoff MARIAs ≥1 identified TI segments with active inflammation with 84% sensitivity, 73% specificity, 85% positive predictive value (PPV), 70% negative predictive value (NPV), and area under the curve (AUC) 0.782 (95% confidence interval [CI] 0.689-0.876). The cutoff MARIAs ≥2 identified TI segments with severe lesions with 87% sensitivity, 76% specificity, 87% PPV, 76% NPV, and AUC 0.814 (95% CI 0.712-0.916). There was poor sensitivity for all colonic segments.

CONCLUSION

The MARIAs is feasible and accurate in reflecting disease activity in the TI, but not in the colon, in children with newly diagnosed CD. Although the MARIAs may be useful for monitoring TI disease activity over time, full assessment continues to require both IC and MRE.

Asymptomatic sacroiliitis detected by magnetic resonance enterography in patients with Crohn's disease: prevalence, association with clinical data, and reliability among radiologists in a multicenter study of adult and pediatric population

OBJECTIVES

Patients with Crohn's disease (CD) usually undergo magnetic resonance enterography (MRE) for evaluating small bowel involvement. Musculoskeletal symptoms are the most frequent extraintestinal manifestation in inflammatory bowel diseases, especially in CD, with sacroiliitis at imaging occurring in about 6-46% of patients and possibly correlating with axial spondyloarthritis. The primary study aim was to assess the prevalence of sacroiliitis in adult and pediatric patients with CD performing an MRE. We also evaluated the inter-rater agreement for MRE sacroiliitis and the association between sacroiliitis and patients' clinical data.

METHOD

We retrospectively identified 100 adult and 30 pediatric patients diagnosed with CD who performed an MRE between December 2012 and May 2020 in three inflammatory bowel disease centers. Two radiologists assessed the prevalence of sacroiliitis at MRE. We evaluated the inter-rater agreement for sacroiliitis with Cohen's kappa and intraclass correlation coefficient statistics and assessed the correlation between sacroiliitis and demographic, clinical, and endoscopic data (Chi-square and Fisher's tests).

RESULTS

The prevalence of sacroiliitis at MRE was 20% in adults and 6.7% in pediatric patients. The inter-rater agreement for sacroiliitis was substantial (k = 0.62, p < 0.001) in the adults and moderate (k = 0.46, p = 0.011) in the pediatric cohort. Age ≥ 50 years and the time between CD diagnosis and MRE (≥ 86.5 months) were significantly associated with sacroiliitis in adult patients (p = 0.049 and p = 0.038, respectively).

CONCLUSIONS

Sacroiliitis is a frequent and reliable abnormality at MRE in adult patients with CD, associated with the age of the patients ≥ 50 years and CD duration.