Computational postprocessing quantification of small bowel motility using magnetic resonance images in clinical practice: An initial experience

Technical Feasibility of Quantitative Measurement of Various Degrees of Small Bowel Motility Using Cine Magnetic Resonance Imaging

OBJECTIVE

Cine magnetic resonance imaging (MRI) has emerged as a noninvasive method to quantitatively assess bowel motility. However, its accuracy in measuring various degrees of small bowel motility has not been extensively evaluated. We aimed to draw a quantitative small bowel motility score from cine MRI and evaluate its performance in a population with varying degrees of small bowel motility.

MATERIALS AND METHODS

A total of 174 participants (28.5 ± 7.6 years; 135 males) underwent a 22-second-long cine MRI sequence (2-dimensional balanced turbo-field echo; 0.5 seconds per image) approximately 5 minutes after being intravenously administered 10 mg of scopolamine-N-butyl bromide to deliberately create diverse degrees of small bowel motility. In a manually segmented area of the small bowel, motility was automatically quantified using a nonrigid registration and calculated as a quantitative motility score. The mean value (MV) of motility grades visually assessed by two radiologists was used as a reference standard. The quantitative motility score's correlation (Spearman's ρ) with the reference standard and performance (area under the receiver operating characteristics curve [AUROC], sensitivity, and specificity) for diagnosing adynamic small bowel (MV of 1) were evaluated.

RESULTS

For the MV of the quantitative motility scores at grades 1, 1.5, 2, 2.5, and 3, the mean ± standard deviation values were 0.019 ± 0.003, 0.027 ± 0.010, 0.033 ± 0.008, 0.032 ± 0.009, and 0.043 ± 0.013, respectively. There was a significant positive correlation between the quantitative motility score and the MV (ρ = 0.531, P < 0.001). The AUROC value for diagnosing a MV of 1 (i.e., adynamic small bowel) was 0.953 (95% confidence interval, 0.923-0.984). Moreover, the optimal cutoff for the quantitative motility score was 0.024, with a sensitivity of 100% (15/15) and specificity of 89.9% (143/159).

CONCLUSION

The quantitative motility score calculated from a cine MRI enables diagnosis of an adynamic small bowel, and potentially discerns various degrees of bowel motility.

[New solutions for an old problem : Current developments in oral contrast agents]

BACKGROUND

Several radiological societies in Europe have so far spoken out in favor of MRI of the small intestine over CT, since MRI is said to provide more detailed image information. Due to the limited availability of MRI machines, long waiting times arise for many patients who clinically require small bowel imaging.

OBJECTIVES

These circumstances guided our search for an improved CT technique that would provide scans that mimic the image impression of T1 sequence in MRI, i.e. with IV contrast-enhanced intestinal wall versus low/no signal lumen.

MATERIAL AND METHODS

The oral use of fat or oil is poorly tolerated by patients, as is the placement of a naso-duodenal tube for air insufflation. We have now succeeded in creating a foamy drink with 44% air content, which is kept stable by protein together with buffers, and can be easily administered orally. CT with the Lumentin® beverage as bowel filling agent has been tested on healthy adult volunteers; oncology patients; and Crohn's disease patients who, for comparison, also underwent MRI of the small bowel with conventional oral contrast.

RESULTS

The results so far with Lumentin® show a very good distribution throughout the entire small intestine with good lumen distension, images with strongly enhanced contrast of the intestinal mucosa, and lesions that are detected at the same or increased frequency as compared with MRI. Side effects were few and mild, and overall fewer than with commonly used oral agents. Lumentin's foamy consistency was unfamiliar to a few patients, but it wasn't difficult to drink.

CONCLUSIONS

The new and innovative luminal HU-negative contrast agent Lumentin® improves the diagnostic CT image quality. In addition, Lumentin® experimental MRI tests have provided promising results, which are currently leading to further clinical MRI studies.

Inflammatory bowel disease cross-sectional imaging: What's new?

Cross-sectional imaging-ultrasonography, computed tomography enterography, and magnetic resonance enterography-is a routine and indispensable tool for patients with Crohn's disease (CD) that helps to detect or monitor disease characteristics before, during, and after CD treatment. New emerging radiological technologies may have further clinical applications in the management of CD. In this review article, we focus on the latest developments in cross-sectional imaging in CD research, including its role in intra- and extra-luminal lesion detection, intestinal inflammation and fibrosis grading, therapeutic response assessment and outcome prediction, postoperative recurrence detection and prediction, and the gut-brain axis.

Automatic detection of Crohn's disease using quantified motility in magnetic resonance enterography: initial experiences

AIM

To report initial experiences of automatic detection of Crohn's disease (CD) using quantified motility in magnetic resonance enterography (MRE).

MATERIALS AND METHODS

From 302 patients, three datasets with roughly equal proportions of CD and non-CD cases with various illnesses were drawn for testing and neural network training and validation. All datasets had unique MRE parameter configurations and were performed in free breathing. Nine neural networks were devised for automatic generation of three different regions of interests (ROI): small bowel, all bowel, and non-bowel. Additionally, a full-image ROI was tested. The motility in an MRE series was quantified via a registration procedure, which, accompanied with given ROIs, resulted in three motility indices (MI). A subset of the indices was used as an input for a binary logistic regression classifier, which predicted whether the MRE series represented CD.

RESULTS

The highest mean area under the curve (AUC) score, 0.78, was reached using the full-image ROI and with the dataset with the highest cine series length. The best AUC scores for the other two datasets were only 0.54 and 0.49.

CONCLUSION

The automatic system was able to detect CD in the group of MRE studies with lower temporal resolution and longer cine series showing potential in primary bowel disorder diagnostics. Larger ROI selections and utilising all available cine series for motility registration yielded slight performance improvements.

Quantified small bowel motility in patients with ulcerative colitis and gastrointestinal symptoms: a pilot study

BACKGROUND

Gastrointestinal (GI) symptoms are common in patients with ulcerative colitis (UC), even when the disease is in remission, possibly due to abnormalities in GI motility. Small bowel motility can be assessed globally and in specific intestinal regions during magnetic resonance enterography (MRE) using a displacement mapping technique.

PURPOSE

To investigate whether small bowel motility in MRE differs between patients with UC and controls, and if altered motility correlates with GI symptoms.

MATERIAL AND METHODS

In 2016-2018, patients who were admitted for MRE, regardless of clinical indication, were consecutively invited to the study. Healthy volunteers were recruited. The participants completed a questionnaire regarding GI symptoms and relevant clinical data were reviewed in the medical records. The dynamic imaging series obtained during MRE were sent for motility mapping and a motility index (MI) was calculated in jejunum, ileum and terminal ileum in all participants.

RESULTS

In total, 224 patients and healthy volunteers were enrolled in the study. Fifteen were diagnosed with UC and 22 were considered healthy controls. In UC, the prevalence of GI symptoms was higher than in controls (P < 0.001), both in remission and in active disease. There was no correlation between GI symptoms and small bowel motility in UC. Jejunal motility was lower in UC than in controls (P = 0.049).

CONCLUSION

Jejunal motility is decreased in UC compared with healthy controls, but there is no relationship between small bowel motility and GI symptoms in UC.

Volumetric analysis of small bowel motility in an unselected cohort of patients with Crohn's disease

BACKGROUND

Quantified terminal ileal motility during magnetic resonance enterography (MRE) has been suggested to be used as a biomarker of Crohn's disease (CD). The aim of the present study was to evaluate this method in clinical practice.

METHODS

Healthy volunteers and all consecutive patients referred to MRE during a 2-year period were asked to participate and complete the Irritable Bowel Syndrome-Symptom Severity Scale (IBS-SSS) to assess gastrointestinal symptoms. Medical records were scrutinized, and motility indices (MIs) were calculated from MR images.

KEY RESULTS

Twenty-two healthy controls and 134 examinations with CD were included (inclusion rate: 76.3%). Patients with CD had increased mural thickness of the terminal ileum, increased fecal calprotectin, and more symptoms than controls. Patients with active CD had increased mural thickness of ileum and terminal ileum, higher MR activity indices, and signs of inflammation in laboratory analyses, but similar symptoms, compared with inactive disease. After exclusion of sole colon disease (n = 13), MI inversely correlated with mural thickness in terminal ileum, and MI was lower in active disease versus controls in ileum (P = .019) and terminal ileum (P = .005), and versus inactive disease in terminal ileum (P = .044). The area under the curve of MI in terminal ileum was 0.736 for active CD against healthy controls (P = .002) and 0.682 for active against inactive CD (P = .001). MIs were similar in controls and inactive CD.

CONCLUSIONS AND INTERFERENCES

MI reflects inflammatory activity in the intestine. Alterations in MI did not explain symptomatology in inactive CD, without measurable inflammatory parameters in morphology or laboratory analyses.

Motility index measured by magnetic resonance enterography is associated with sex and mural thickness

BACKGROUND

Recently, a technique has been developed to use magnetic resonance enterography (MRE) for the evaluation of small bowel motility. The hypothesis was that assessment of the motility index (MI) should reflect differences in motility between clinical conditions.

AIM

To aim of the present observational, cross-sectional study was to evaluate the use of the MI in daily clinical practice.

METHODS

All consecutive patients aged 18-70 years who were referred for MRE at the Department of Radiology during a 2-year period were asked to participate. Healthy volunteers were included as controls. MRE was prepared and conducted in accordance with clinical routines. On the day of examination, all the participants had to complete the visual analog scale for irritable bowel syndrome (IBS) and IBS-symptom severity scale. Maps of MI were calculated from dynamic MR images. ANOVA was used to evaluate differences in MI between groups, classified as healthy, Crohn’s disease, ulcerative colitis, IBS, other assorted disorders and dysmotility. Logistic and linear regression were applied to the MI values. All medical records were scrutinized for medical history.

RESULTS

In all, 224 examinations were included (inclusion prevalence 76.3%), with 22 controls and 202 patients. There was a significant difference in the MI of the jejunum (P = 0.021) and terminal ileum (P = 0.007) between the different groups. The MI was inversely associated with the mural thickness of the terminal ileum in men (P < 0.001) and women (P = 0.063) after adjustments, and tended to be lower in men than in women (P = 0.056). Subjectively observed reduction of motility on MRI was accomplished by reduced MI of terminal ileum in men (P < 0.001) and women (P = 0.030). In women, diarrhea was inversely associated with the MI of the jejunum (P = 0.029), and constipation was positively associated with the MI of the terminal ileum (P = 0.039).

CONCLUSION

Although MIs differ across diseases, a lower MI of the terminal ileum is mainly associated with male sex and an increased mural thickness. Symptoms are weakly associated with the MI.

Cross-sectional imaging for assessing intestinal fibrosis in Crohn's disease

More than 30% of patients with Crohn's disease (CD) develop fibrotic strictures in the bowel as the disease progresses. Excessive deposition of extracellular matrix components in the submucosa and smooth muscle hypertrophy or hyperplasia are the main features of fibrosis in CD. Cross-sectional imaging technology provides a wealth of information on the anatomy, histological composition, and physiological function of the bowel, allowing for a non-invasive and complete evaluation of associated abnormalities. This review summarizes recent advances in and the potential technologies of cross-sectional imaging for assessing intestinal fibrosis in CD, including ultrasound imaging, computed tomography, and magnetic resonance imaging.

Abnormal gut motility in inflammatory bowel disease: an update

BACKGROUND

There is substantial evidence linking disturbed gastrointestinal motility to inflammation. Thus, it is not surprising that abnormalities of gastrointestinal motility play a role in inflammatory bowel disease (IBD), affecting patient outcomes. We performed a review of the literature to investigate the relationship between abnormal gut motility and IBD.

METHODS

With an extensive literature search, we retrieved the pertinent articles linking disturbed gut motility to IBD in various anatomical districts.

RESULTS

The evidence in the literature suggests that abnormal gastrointestinal motility plays a role in the clinical setting of IBD and may confuse the clinical picture.

CONCLUSIONS

Abnormal gut motility may be important in the clinical setting of IBD. However, additional data obtained with modern techniques (e.g., magnetic resonance imaging) are needed to individuate in a more precise manner gastrointestinal motor dysfunctions, to understand the nature of clinical manifestations and properly tailor the treatment of patients.

Evaluation of compressed sensing MRI for accelerated bowel motility imaging

Background

To investigate the feasibility of compressed sensing and parallel imaging (CS-PI)-accelerated bowel motility magnetic resonance imaging (MRI) and to compare its image quality and diagnostic quality to conventional sensitivity encoding (SENSE) accelerated scans.

Methods

Bowel MRI was performed in six volunteers using a three-dimensional balanced fast field-echo sequence. Static scans were performed after the administration of a spasmolytic agent to prevent bowel motion artefacts. Fully sampled reference scans and multiple prospectively 3× to 7× undersampled CS-PI and SENSE scans were acquired. Additionally, fully sampled CS-PI and SENSE scans were retrospectively undersampled and reconstructed. Dynamic scans were performed using 5× to 7× accelerated scans in the presence of bowel motion. Retrospectively, undersampled scans were compared to fully sampled scans using structural similarity indices. All reconstructions were visually assessed for image quality and diagnostic quality by two radiologists.

Results

For static imaging, the performance of CS-PI was lower than that of fully sampled and SENSE scans: the diagnostic quality was assessed as adequate or good for 100% of fully sampled scans, 95% of SENSE, but only for 55% of CS-PI scans. For dynamic imaging, CS-PI image quality was scored similar to SENSE at high acceleration. Diagnostic quality of all scans was scored as adequate or good; 55% of CS-PI and 83% of SENSE scans were scored as good.

Conclusion

Compared to SENSE, current implementation of CS-PI performed less or equally good in terms of image quality and diagnostic quality. CS-PI did not show advantages over SENSE for three-dimensional bowel motility imaging.

Detecting the effects of a standardized meal challenge on small bowel motility with MRI in prepared and unprepared bowel

OBJECTIVE

MRI is increasingly used to evaluate small bowel contractility. The objective of this study was to validate a clinically practical stimulation test (300-kcal meal) for small bowel motility.

METHODS

Thirty-one healthy subjects underwent dynamic MRI to capture global small bowel motility after ±10h fasting, of which 15 underwent bowel preparation consisting of 1 L 2.5% mannitol solution and 16 did not. Each subject underwent (1) a baseline motility scan (2) a food challenge (3) a post-challenge scan, and (4) second post-challenge scan (after ±20 minutes). This protocol was repeated within 2 weeks. Motility was quantified using a validated motility assessment technique.

KEY RESULTS

Motility in prepared subjects at baseline was significantly higher than motility in unprepared subjects (0.36 AU vs 0.18 AU, P < 0.001). In the prepared group, the food challenge produced an 8% increase in motility (P = 0.33) while in the unprepared subjects a significant increase of 30% was observed (P < 0.001). Responses to food remained insignificant (P = 0.21) and significant (P = 0.003), for the prepared and unprepared subjects, respectively, ±20 minutes post food challenge. These results were confirmed in the repeated scan session.

CONCLUSION & INFERENCES

A significant response to a 300-kcal meal was measured within 10 minutes in unprepared bowel, supporting the clinical use of this challenge to provoke and assess motility changes. A caloric challenge did not produce an observable increase in motility in mannitol prepared subjects.

Will MRI of gastrointestinal function parallel the clinical success of cine cardiac MRI?

Cine cardiac MRI is generally accepted as the "gold-standard" for functional myocardial assessment. It only took a few years after the development of commercial MRI systems for functional cardiac imaging to be developed, with electrocardiogram (ECG)-gated cine imaging first reported in 1988. The function of the gastrointestinal (GI) tract is more complex to study compared to the heart. However, the idea of having a non-invasive tool to study the GI function that also allows the concurrent assessment of different aspects of this function has become more and more attractive in the gastroenterological field. This review summarises key literature of the last 5 years to describe the current status of MRI in respect to the evaluation of GI function, highlighting the gaps and challenges and the future prospects. As the clinical application of a new technique requires that its clinical utility is confirmed by demonstration of its ability to enable clinicians to make a diagnosis and/or predict the treatment response, this review also considers whether or not this has been achieved, and how MRI has been validated against techniques currently recognised as the gold standard in clinical practice.

Impact of gastrointestinal disease states on oral drug absorption – implications for formulation design – a PEARRL review

Objectives

Drug product performance in patients with gastrointestinal (GI) diseases can be altered compared to healthy subjects due to pathophysiological changes. In this review, relevant differences in patients with inflammatory bowel diseases, coeliac disease, irritable bowel syndrome and short bowel syndrome are discussed and possible in vitro and in silico tools to predict drug product performance in this patient population are assessed.

Key findings

Drug product performance was altered in patients with GI diseases compared to healthy subjects, as assessed in a limited number of studies for some drugs. Underlying causes can be observed pathophysiological alterations such as the differences in GI transit time, the composition of the GI fluids and GI permeability. Additionally, alterations in the abundance of metabolising enzymes and transporter systems were observed. The effect of the GI diseases on each parameter is not always evident as it may depend on the location and the state of the disease. The impact of the pathophysiological change on drug bioavailability depends on the physicochemical characteristics of the drug, the pharmaceutical formulation and drug metabolism. In vitro and in silico methods to predict drug product performance in patients with GI diseases are currently limited but could be a useful tool to improve drug therapy.

Summary

Development of suitable in vitro dissolution and in silico models for patients with GI diseases can improve their drug therapy. The likeliness of the models to provide accurate predictions depends on the knowledge of pathophysiological alterations, and thus, further assessment of physiological differences is essential.

Dynamic MRI for bowel motility imaging-how fast and how long?

Objective:

Dynamic imaging of small intestinal motility is an increasingly common research method to examine bowel physiology in health and disease. However, limited data exist to guide imaging protocols with respect to quantitative analysis. The purpose of this study is to define the required temporal resolution and scan duration in dynamic MRI for small bowel motility assessment.

Methods:

Six healthy volunteers underwent motility imaging with MR enterography using breath-hold protocol. A coronal two-dimensional balanced fast field echo sequence was used to acquire dynamic data at a high temporal resolution of 10 frames per second (fps). Motility was quantified by generating a registration-derived motility index for local and global regions of bowel. To evaluate temporal resolution and scan duration, the data were undersampled and the scan length was varied to determine the impact on motility index.

Results:

The mean motility index stabilizes at a temporal resolution of 1 fps (median absolute percentage change 1.4% for global and 1.9% for local regions of interest). The mean motility index appears to stabilize for scan durations of 15 s or more in breath-hold (median absolute % change 2.8% for global and 1.7% for local regions of interest).

Conclusion:

A temporal resolution of at least 1 fps and a scan duration of at least 15 s is necessary in breath-hold scans for consistent motility observations. The majority of small bowel motility studies to date are in line with these requirements.

Advances in knowledge:

This study suggests the minimum temporal resolution and scan duration required in breath-hold scans to obtain robust measurements of small bowel motility from MRI.

Evaluation of gastrointestinal motility with MRI: Advances, challenges and opportunities

Dynamic magnetic resonance imaging (MRI) of gastrointestinal motility has developed rapidly over the past few years. The non-invasive and non-ionizing character of MRI is an important advantage together with the fact that it is fast and can visualize the entire gastrointestinal tract. Advances in imaging and quantification techniques have facilitated assessment of gastric, small intestinal, and colonic motility in a clinical setting. Automated quantitative motility assessment using dynamic MRI meets the need for non-invasive techniques. Recently, studies have begun to examine this technique in patients, including those with IBD, pseudo-obstruction and functional bowel disorders. Remaining challenges for clinical implementation are processing the large amount of data, standardization and validation of the numerous MRI metrics and subsequently assessment of the potential role of dynamic MRI. This review examines the methods, advances, and remaining challenges of evaluation of gastrointestinal motility with MRI. It accompanies an article by Khalaf et al. in this journal that describes a new protocol for assessment of pan-intestinal motility in fasted and fed state in a single MRI session.

Small Bowel Motility

PURPOSE OF REVIEW

Small bowel motility disorders constitute a relatively small but important segment of clinical gastroenterology. Presenting features encompass a broad range of symptom manifestations and severity: from chronic functional-type complaints to life-threatening nutritional impairment. Diagnostic assessment of patients with suspected intestinal motility disorders is often hampered by the complexity of measuring intestinal contractile activity in humans. In this review, we describe and critically comment the main current and forthcoming methodologies.

RECENT FINDINGS

Beyond conventional small bowel manometry, radiological methods, and intestinal transit tests that have been available for several decades, now we focus on novel methodologies such as high-resolution manometry, magnetic resonance methodology, and endoluminal capsule image analysis. Gradual introduction of new approaches to diagnostic investigation of patients with suspected intestinal motility disorders should facilitate a less invasive and more accurate characterization of disturbed motor function. Enhanced understanding of the pathophysiological basis of clinical conditions should allow better application of therapeutic approaches that are also highlighted in this review.