Time-resolved three-dimensional MR imaging of gastric emptying modified by IV administration of erythromycin

Non-uniform gastric wall kinematics revealed by 4D Cine magnetic resonance imaging in humans

BACKGROUND

Assessment of gastric function in humans has relied on modalities with varying degrees of invasiveness, which are usually limited to the evaluation of single aspects of gastric function, thus requiring patients to undergo a number of often invasive tests for a full clinical understanding. Therefore, the development of a non-invasive tool able to concurrently assess multiple aspects of gastric function is highly desirable for both research and clinical assessments of gastrointestinal (GI) function. Recently, technological advances in magnetic resonance imaging (MRI) have provided new tools for dynamic (or "cine") body imaging. Such approaches can be extended to GI applications.

METHODS

In the present work, we propose a non-invasive assessment of gastric function using a four-dimensional (4D, volumetric cine imaging), free-breathing MRI sequence with gadolinium-free contrast enhancement achieved through a food-based meal. In healthy subjects, we successfully estimated multiple parameters describing gastric emptying, motility, and peristalsis propagation patterns.

KEY RESULTS

Our data demonstrated non-uniform kinematics of the gastric wall during peristaltic contraction, highlighting the importance of using volumetric data to derive motility measures.

CONCLUSIONS & INFERENCES

MRI has the potential of becoming an important clinical and gastric physiology research tool, providing objective parameters for the evaluation of impaired gastric function.

Effects of Promotility Agents on Gastric Emptying and Symptoms: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Studies have reported a lack of association between improvements in gastric emptying (GE) and upper gastrointestinal (UGI) symptoms with promotility drugs. However, GE test methods were suboptimal in some studies. We assessed improvements in GE and UGI symptoms in patients given promotility agents in studies with optimal or moderate test methods (scintigraphy or breath test, solid meal, >2 hours duration) compared to studies with suboptimal GE test methods.

METHODS

With an expert librarian, we completed an extensive search of publications in the Ovid MEDLINE (1946 to present), EMBASE (1988 to January 2018), and EBM Reviews Cochrane Central Register of Controlled Trials, without restrictions on language or year. Two independent reviewers evaluated the following inclusion criteria: randomized, blinded, parallel, or crossover trials of 5HT₄ agonists, D₂ receptor antagonist, or ghrelin agonists; trials that measured change in GE (T_1/2) or composite UGI symptoms; trials of patients with functional dyspepsia and gastroparesis; and trials of GE test methods. Standardized mean differences (units expressed as SD) were used to standardize symptom assessments that were not uniform across studies. Random effects model was used to analyze data and meta-regression was used to evaluate the association between change in GE and UGI symptoms.

RESULTS

Of 899 studies considered, 22 studies assessed change in GE; 23 evaluated UGI symptoms; and 14 evaluated GE and UGI symptoms. Promotility agents significantly accelerated GE (T_1/2) in all studies (mean reduction in T_1/2, 16.3 minutes; 95% confidence interval, -22.1 to -10.6 minutes) and in studies that used optimal GE test methods (mean reduction in T_1/2, 23.6 minutes; 95% confidence interval, -32.3 to -14.9 minutes). Promotility agents also significantly reduced UGI symptoms (mean reduction, 0.25 SD; 95% confidence interval, -0.37 to -0.13 SD). Meta-regression found no significant association between change in GE and UGI symptoms. However, when only studies with optimal GE test methods were evaluated, there was a significant positive association between improvement in GE and UGI symptoms (P = .02).

CONCLUSIONS

In a meta-analysis of published trials, we found promotility agents to significantly accelerate GE (when optimal test methods were used) and to produce significant improvements in UGI symptoms.

Indications and selection of MR enterography vs. MR enteroclysis with emphasis on patients who need small bowel MRI and general anaesthesia: results of a survey

Aims

To survey the perceived indications for magnetic resonance imaging of the small bowel (MRE) by experts, when MR enteroclysis (MREc) or MR enterography (MREg) may be chosen, and to determine how the approach to MRE is modified when general anaesthesia (GA) is required.

Materials and methods

Selected opinion leaders in MRE completed a questionnaire that included clinical indications (MREg or MREc), specifics regarding administration of enteral contrast, and how the technique is altered to accommodate GA.

Results

Fourteen responded. Only the diagnosis and follow-up of Crohn’s disease were considered by over 80 % as a valid MRE indication. The remaining indications ranged between 35.7 % for diagnosis of caeliac disease and unknown sources of gastrointestinal bleeding to 78.6 % for motility disorders. The majority chose MREg over MREc for all indications (from 100 % for follow-up of caeliac disease to 57.7 % for tumour diagnosis). Fifty per cent of responders had needed to consider MRE under GA. The most commonly recommended procedural change was MRI without enteral distention. Three had experience with intubation under GA (MREc modification).

Conclusion

Views were variable. Requests for MRE under GA are not uncommon. Presently most opinion leaders suggest standard abdominal MRI when GA is required.

Main messages

• Experts are using MRE for various indications.

• Requests for MRE under general anaesthesia are not uncommon.

• Some radiologists employ MREc under general anaesthesia; others do not distend the small bowel.

Enhanced Intestinal Motility during Oral Glucose Tolerance Test after Laparoscopic Sleeve Gastrectomy: Preliminary Results Using Cine Magnetic Resonance Imaging

Background

Enhanced secretion of glucagon-like peptide-1 (GLP-1) has been suggested as a possible mechanism underlying the improvement in type 2 diabetes mellitus (T2DM) after laparoscopic sleeve gastrectomy (LSG). However, the reason for enhanced GLP-1 secretion during glucose challenge after LSG remains unclear because LSG does not include intestinal bypass. In this study, we focused on the effects of LSG on GLP-1 secretion and intestinal motility during the oral glucose tolerance test (OGTT) using cine magnetic resonance imaging (MRI) before and 3 months after LSG.

Methods

LSG was performed in 12 obese patients with a body mass index >35 kg/m². Six patients had T2DM. OGTT was performed before and 3 months after the surgery. Body weight, hemoglobin A1c (HbA1c), and GLP-1 levels during OGTT were examined, and intestinal motility during OGTT was assessed using cine MRI.

Results

Body weight was significantly decreased after surgery in all the cases. HbA1c was markedly decreased in all the diabetic subjects. In all cases, GLP-1 secretion during OGTT was enhanced and cine MRI showed markedly increased intestinal motility at 15 and 30 min during OGTT after LSG.

Conclusions

LSG leads to accelerated intestinal motility and reduced intestinal transit time, which may be involved in the mechanism underlying enhanced GLP-1 secretion during OGTT after LSG.

Assessment of small bowel motility function with cine-MRI using balanced steady-state free precession sequence

PURPOSE

To evaluate the use of cine-magnetic resonance imaging (MRI) with a steady-state free precession sequence to monitor and assess small bowel motility.

MATERIALS AND METHODS

Sequential MRI, using a balanced steady-state free precession sequence, was performed in eight healthy male volunteers at 0, 15, 30, 45, and 60 minutes after oral administration of 1500 mL of nonabsorbable fluid to monitor small bowel contractions. Using the cine-mode display, small bowel contractions were reviewed and the luminal diameter was measured on each image to obtain frequency and amplitude of bowel contractions.

RESULTS

The oral preparation was well tolerated without major complications. Cine-MRI provided high temporal, spatial, and contrast resolution for monitoring bowel contractions. Mean values with standard deviations of frequency and amplitude of bowel contractions were 6.0 ± 2.98/min and 10.4 ± 4.53 mm, respectively, and were 5.1 ± 3.38/min and 9.59 ± 5.57 mm at the jejunal loops and 6.9 ± 2.22/min and 11.2 ± 3.06 mm at the ileal loops. With the passage of luminal fluid, frequency of bowel contractions decreased and the bowels tended to pause their contractions.

CONCLUSION

Cine-MRI provides sufficient dynamic images to observe small bowel contractions. Measurement of bowel caliber permits calculation of amplitude and frequency of the contractions for characterization and quantitative assessment of small bowel motility function.

Assessment of gastrointestinal motor functions by MRI: a comprehensive review

BACKGROUND

Magnetic resonance imaging (MRI) is a useful technique for evaluating gastrointestinal (GI) motor functions because it provides multi-planar imaging capability, high imaging speed, good spatial resolution and excellent soft tissue contrast. Moreover, multiple parameters of GI function can be assessed non-invasively during a single study.

PURPOSE

This critical review of the literature discusses the strengths and limitations of MRI for evaluating GI motor functions.

MRI for the evaluation of gastric physiology

Background:

Evaluation of gastric physiology (gastric emptying and motility) is important for the diagnosis of disturbances such as functional dyspepsia. MRI is a non-invasive technique that allows simultaneous registration of gastric emptying and motility.

Aim:

To provide an overview of the literature of studies that used MRI as a tool for evaluation of gastric function in both research and clinical settings.

Materials and methods:

A MEDLINE search was performed (1990–2008) directed at the radiology and gastroenterology literature on gastric physiology. Key words that were used included: functional tests, gastric emptying, gastric motility, gastric physiology and MRI. Twenty-five articles fulfilled the inclusion criteria and were included in the analysis.

Results and conclusion:

Over the last decade, MRI has developed as a reliable, non-invasive method for detailed evaluation of gastric emptying and motility without the disadvantages of ionizing radiation and without the use of intragastric catheters that influence gastric physiology.

Stomach dysfunction in diabetes mellitus: emerging technology and pharmacology

Gastroparesis and other types of gastric dysfunction result in substantial morbidity in diabetes patients. The pathophysiology of these disorders is incompletely understood. This article reviews techniques applicable to the assessment of gastric function in diabetes patients, including the measurement of emptying, accommodation, and contractility. Available treatment options are also reviewed, including novel yet unapproved serotonin 5-HT(4) agonist pharmacological treatments, as well as the role of endoscopic, surgical, and device treatments of gastroparesis.

Gastroparesis: current concepts and management

Delayed gastric emptying in the absence of mechanical obstruction is referred to as gastroparesis. Symptoms that are often attributed to gastroparesis include postprandial fullness, nausea, and vomiting. Although tests of gastric motor function may aid diagnostic labeling, their contribution to determining the treatment approach is often limited. Although clinical suspicion of gastroparesis warrants the exclusion of mechanical causes and serum electrolyte imbalances, followed by empirical treatment with a gastroprokinetic such as domperidone or metoclopramide, evidence that these drugs are effective for patients with gastroparesis is far from overwhelming. In refractory cases with severe weight loss, invasive therapeutics such as inserting a feeding jejunostomy tube, intrapyloric injection of botulinum toxin, surgical (partial) gastrectomy, and implantable gastric electrical stimulation are occasionally considered.

Methods for measurement of gastric motility

There is an array of tests available to measure gastric motility. Some tests measure end points, such as gastric emptying, that result from several different functions, whereas other tests are more specific and test only a single parameter, such as contractility. This article reviews the tests most commonly available in practice and research to evaluate in vivo the gastric functions of emptying, accommodation, contractility, and myoelectrical activity. The rationale for testing, the relative strengths and weaknesses of each test, and technical details are summarized. We also briefly indicate the applications and validations of the tests for use in experimental animal studies.

Time-resolved dynamic contrast-enhanced MR urography for the evaluation of ureteral peristalsis: initial experience

PURPOSE

To determine the feasibility of time-resolved dynamic contrast-enhanced magnetic resonance urography (MRU) for the evaluation of ureteral peristalsis using a data-sharing 3D gradient echo sequence with spiral k-space filling.

MATERIALS AND METHODS

Eight patients (M=3, F=5, mean 48.1 years) were referred for MRU for the evaluation for renal mass (n=3), hematuria (n=2), urinary tract tuberculosis (n=1), postoperative bladder cancer (n=1), and postoperative ureteric reimplantation (n=1). Dynamic MRU was performed for 120 seconds at 1.5T after intravenous furosemide and gadolinium administration using an oblique sagittal, time-resolved T1 3D gradient echo sequence with 1 second effective temporal resolution. Study quality was assessed based on artifacts and extent of ureteric visualization. Frequency of peristalsis from the renal pelvis to urinary bladder was evaluated for each subject.

RESULTS

A total of 16 ureters were examined. Image quality was good in four ureters, satisfactory in 11 ureters, and poor in one ureter. Mean peristaltic frequency was 3.5 waves per minute (range, 2.5-6.5 waves/minute) in normal ureters (n=11). Five ureters were considered abnormal (one urinary tract tuberculosis and four postsurgical ureters), and all had decreased or no peristalsis (0-1.5 waves per minute).

CONCLUSION

MRU using a time-resolved, data-sharing 3D contrast-enhanced technique is able to demonstrate ureteral peristalsis and permits quantification of ureteral peristaltic frequency.

MRI scoring system including dynamic motility evaluation in assessing the activity of Crohn's disease of the terminal ileum

RATIONALE AND OBJECTIVES

We sought to investigate the value of a MRI scoring system including dynamic motility evaluation in the assessment of small bowel Crohn's disease activity.

MATERIALS AND METHODS

From March 2005 to December 2006, 52 patients with suspected Crohn's disease onset or relapse underwent MRI on a 1.5-T magnet. Bowel distention was achieved orally assuming a mean of 1.6 L of a polyethyleneglycol (PEG) preparation. Per-patient assessment of disease activity was based on a scoring system including evaluation of morphology and motility of the small bowel and perivisceral structures (true-FISP, cine-true-FISP, and HASTE T2W sequences) and dynamic assessment of parietal contrast enhancement (FLASH T1W sequence). Patients were included in three categories, using endoscopic biopsy as the standard reference: no activity/quiescent disease, mild activity, or moderate-to-severe activity. Patients without terminal ileum involvement were excluded from data analysis.

RESULTS

MRI allowed a detailed and panoramic evaluation of the small bowel in all subjects examined. MRI properly assessed 14 of 16 (87.5%) cases of no activity/quiescent disease, 12 of 14 (85.7%) cases of mild activity, and 15 of 15 (100%) cases of severe activity. Overall, activity score led to a per-patient misdiagnosis of disease activity in a nonsignificant proportion of subjects (4 of 45; 8.8%) (P > .05), determining two false-positive and two false-negative results of mild disease activity. Sensitivity, specificity, PPV, NPV, and overall accuracy in assessing disease activity were 93.1%, 87.5%, 93.1%, 87.5%, and 91.1%, respectively.

CONCLUSION

Accurate assessment of Crohn's disease activity is achieved by using an activity score providing an overall interpretation of MRI findings.

The difficult patient with gastroparesis

Gastroparesis is often difficult to manage. First of all, exact criteria for making a diagnosis of gastroparesis have not been established, and merely finding delayed gastric emptying does not justify the label. Furthermore, the relationship between symptoms and gastric emptying rate is poor, and the number of therapies with proven efficacy is extremely limited. A number of technical investigations are helpful to establish the anatomy and motor function of the upper gastrointestinal tract. In most cases where gastroparesis can be presumed or established, prokinetic therapy will be tried. A number of agents are available, with variable efficacy and tolerance. Rarely, in case of debilitating refractory symptoms, experimental or invasive therapies can be tried such as injection of botulinum toxin, enteral feeding tube insertion, gastric electrical stimulation or surgery.

New imaging in neurogastroenterology: an overview

Advances in imaging are being introduced initially as research tools and subsequently as clinical diagnostic tests. These investigations include modifications of the standard gastric emptying by scintigraphy to include application of intraluminal ultrasound to image sustained contractions and longitudinal shortening in the oesophagus, 2- and 4-h images, volumetric measurements to measure gastric volume, magnetic resonance (MR) imaging to appraise the structure and function of the rectal evacuation process, and brain imaging as a surrogate for the investigation of the brain's contribution to functional gastrointestinal disorders and chronic pain syndromes. There is a need for rigorous validation and measurement of the performance characteristics of these tests. Given the impact of gastric emptying at 4 h and single photon emission computerized tomography (SPECT) imaging for measuring gastric volumes on research and clinical practice, it is anticipated that, once validated, these different techniques are likely to have a significant impact on neurogastroenterology and, potentially, replace more invasive procedures.

Gastrointestinal hormone abnormalities and G and D cells in functional dyspepsia patients with gastric dysmotility

AIM: To investigate the relationship between gastric dysmotility, gastrointestinal hormone abnormalities, and neuroendocrine cells in gastrointestinal mucosa in patients with functional dyspepsia (FD).

METHODS: Gastric emptying was assessed with solid radiopaque markers in 54 FD patients, and the patients were divided into two groups according to the results, one with delayed gastric emptying and the other with normal gastric emptying. Seventeen healthy volunteers acted as normal controls. Fasting and postprandial plasma levels and gastroduodenal mucosal levels of gastrointestinal hormones gastrin, somatostatin (SS) and neurotensin (NT) were measured by radioimmunoassay in all the subjects. G cells (gastrin-producing cells) and D cells (SS-producing cells) in gastric antral mucosa were immunostained with rabbit anti-gastrin polyclonal antibody and rabbit anti-SS polyclonal antibody, respectively, and analyzed quantitatively by computerized image analysis.

RESULTS: The postprandial plasma gastrin levels, the fasting and postprandial plasma levels and the gastric and duodenal mucosal levels of NT were significantly higher in the FD patients with delayed gastric emptying than in those with normal gastric emptying and normal controls. The number and gray value of G and D cells and the G cell/D cell number ratio did not differ significantly between normal controls and the FD patients with or without delayed gastric emptying.

CONCLUSION: Our findings suggest that the abnormalities of gastrin and NT may play a role in the pathophysiology of gastric dysmotility in FD patients, and the abnormality of postprandial plasma gastrin levels in FD patients with delayed gastric emptying is not related to the changes both in the number and gray value of G cells and in the G cell/D cell number ratio in gastric antral mucosa.

Measuring tongue volumes and visualizing the chewing and swallowing process using real-time TrueFISP imaging--initial clinical experience in healthy volunteers and patients with acromegaly

This study assessed both two-dimensional (2D) TrueFISP imaging for quantifying tongue volume and real-time TrueFISP imaging for evaluating chewing and swallowing in healthy volunteers and patients with acromegaly. In 50 healthy volunteers, tongue volumes were measured using a 2D TrueFISP sequence. Chewing and swallowing were visualized using a real-time TrueFISP sequence. Ten patients with acromegaly were examined twice with the same magnetic resonance imaging protocol: once prior to therapy and a second time 6 months after therapy. Prior to therapy, healthy volunteers had an average tongue volume of 140 ml for men and 90 ml for women, and patients with acromegaly had an average tongue volume of 180 ml for men and 145 ml for women. However, 6 months after therapy the mean tongue volumes in patients with acromegaly had decreased to 154 ml in the men and to 125 ml in the women. The chewing and swallowing process was normal in all volunteers. Prior to therapy, just two patients showed a chewing and swallowing pathology, which disappeared after therapy. Patients with acromegaly had larger tongue volumes than healthy volunteers, and TrueFISP imaging proved feasible for visualizing chewing and swallowing in real time and is capable of detecting possible pathologies. Furthermore, TrueFISP imaging can be used to monitor therapeutic approaches in patients with acromegaly.

Real-time high-resolution MRI for the assessment of gastric motility: pre- and postpharmacological stimuli

PURPOSE

To determine the practicality of MRI using a new real-time sequence for the assessment of gastric motion, and quantify the effects of motility-modifying substances.

MATERIALS AND METHODS

Six healthy volunteers ingested 400 mL of a high-calorie liquid nutrient. Two-dimensional real-time TrueFISP sequences were acquired for up to 30 minutes following the ingestion. The acquisition plane was chosen parallel to the axis of the gastric antrum. The examination was performed on three separate days with and without i.v. administration of 10 mg metoclopramide or 20 mg scopolamine. A motility index was calculated for each real-time data set.

RESULTS

Delineation of the gastric lumen proved easy and robust. The intravenous application of motility-modifying agents resulted in significant changes in the motility index. The administration of metoclopramide resulted in an average increase of the index by a factor of 1.5, whereas the application of scopolamine led to a decrease of the index by a factor of 3.0.

CONCLUSION

TrueFISP MRI performed well in depicting the gastric lumen and assessing gastric motility. Furthermore, we were able to evaluate and quantify the effect of motility-modifying agents. The noninvasive nature of MRI makes this imaging modality an attractive alternative to conventional invasive diagnostic tools for gastric motility disorders and monitoring of therapy.