Vagus nerve stimulation promotes gastric emptying by increasing pyloric opening measured with magnetic resonance imaging.
Lu K-H,Cao J,Oleson S,Ward M P,Phillips R J,Powley T L,Liu Z
Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society
BACKGROUND:Vagus nerve stimulation (VNS) is an emerging electroceutical therapy for remedying gastric disorders that are poorly managed by pharmacological treatments and/or dietary changes. Such therapy seems promising as the vagovagal neurocircuitry modulates the enteric nervous system to influence gastric functions. METHODS:Here, the modulatory effects of left cervical VNS on gastric emptying in rats were quantified using a (i) feeding protocol in which the animal voluntarily consumed a postfast, gadolinium-labeled meal and (ii) a non-invasive imaging method to measure antral motility, pyloric activity and gastric emptying based on contrast-enhanced magnetic resonance imaging (MRI) and computer-assisted image processing pipelines. KEY RESULTS:Vagus nerve stimulation significantly accelerated gastric emptying (sham vs VNS: 29.1% ± 1.5% vs 40.7% ± 3.9% of meal emptied per 4 hours), caused a greater relaxation of the pyloric sphincter (sham vs VNS: 1.5 ± 0.1 vs 2.6 ± 0.4 mm cross-sectional area of lumen), and increased antral contraction amplitude (sham vs VNS: 23.3% ± 3.0% vs 32.5% ± 3.0% occlusion), peristaltic velocity (sham vs VNS: 0.50 ± 0.02 vs 0.67 ± 0.03 mm s ), but not its contraction frequency (sham vs VNS: 6.1 ± 0.2 vs 6.4 ± 0.2 contractions per minute, P = .22). The degree to which VNS relaxed the pylorus was positively correlated with gastric emptying rate (r = .5887, P < .001). CONCLUSIONS & INFERENCES:The MRI protocol employed in this study is expected to enable advanced preclinical studies to understand stomach pathophysiology and its therapeutics. Results from this study suggest an electroceutical treatment approach for gastric emptying disorders using cervical VNS to control the degree of pyloric sphincter relaxation.
10.1111/nmo.13380
Measurement of fasted state gastric antral motility before and after a standard bioavailability and bioequivalence 240 mL drink of water: Validation of MRI method against concomitant perfused manometry in healthy participants.
Heissam Khaled,Abrehart Nichola,Hoad Caroline L,Wright Jeff,Menys Alex,Murray Kathryn,Glover Paul M,Hebbard Geoffrey,Gowland Penny A,Baker Jason,Hasler William L,Spiller Robin C,Corsetti Maura,Brasseur James G,Hens Bart,Shedden Kerby,Dickens Joseph,Mudie Deanna M,Amidon Greg E,Amidon Gordon L,Marciani Luca
PloS one
OBJECTIVE:The gastrointestinal environment in which drug products need to disintegrate before the drug can dissolve and be absorbed has not been studied in detail due to limitations, especially invasiveness of existing techniques. Minimal in vivo data is available on undisturbed gastrointestinal motility to improve relevance of predictive dissolution models and in silico tools such as physiologically-based pharmacokinetic models. Recent advances in magnetic resonance imaging methods could provide novel data and insights that can be used as a reference to validate and, if necessary, optimize these models. The conventional method for measuring gastrointestinal motility is via a manometric technique involving intubation. Nevertheless, it is feasible to measure gastrointestinal motility with magnetic resonance imaging. The aim of this study was is to develop and validate a magnetic resonance imaging method using the most recent semi-automated analysis method against concomitant perfused manometry method. MATERIAL AND METHODS:Eighteen healthy fasted participants were recruited for this study. The participants were intubated with a water-perfused manometry catheter. Subsequently, stomach motility was assessed by cine-MRI acquired at intervals, of 3.5min sets, at coronal oblique planes through the abdomen and by simultaneous water perfused manometry, before and after administration of a standard bioavailability / bioequivalence 8 ounces (~240mL) drink of water. The magnetic resonance imaging motility images were analysed using Spatio-Temporal Motility analysis STMM techniques. The area under the curve of the gastric motility contractions was calculated for each set and compared between techniques. The study visit was then repeated one week later. RESULTS:Data from 15 participants was analysed. There was a good correlation between the MRI antral motility plots area under the curve and corresponding perfused manometry motility area under the curve (r = 0.860) during both antral contractions and quiescence. CONCLUSION:Non-invasive dynamic magnetic resonance imaging of gastric antral motility coupled with recently developed, semi-automated magnetic resonance imaging data processing techniques correlated well with simultaneous, 'gold standard' water perfused manometry. This will be particularly helpful for research purposes related to oral absorption where the absorption of a drug is highly depending on the underlying gastrointestinal processes such as gastric emptying, gastrointestinal motility and availability of residual fluid volumes. CLINICAL TRIAL:This trial was registered at ClinicalTrials.gov as NCT03191045.
10.1371/journal.pone.0241441
MRI-Based Quantification of Pan-Alimentary Function and Motility in Subjects with Diabetes and Gastrointestinal Symptoms.
Journal of clinical medicine
Diabetes-induced gastrointestinal (GI) symptoms are common but difficult to correctly diagnose and manage. We used multi-segmental magnetic resonance imaging (MRI) to evaluate structural and functional GI parameters in diabetic patients and to study the association with their symptomatic presentation. Eighty-six participants (46 with diabetes and GI symptoms, 40 healthy controls) underwent baseline and post-meal MRI scans at multiple timepoints. Questionnaires were collected at inclusion and following the scans. Data were collected from the stomach, small bowel, and colon. Associations between symptoms and collected data were explored. Utilizing machine learning, we determined which features differentiated the two groups the most. The patient group reported more symptoms at inclusion and during MRI scans. They showed 34% higher stomach volume at baseline, 40% larger small bowel volume, 30% smaller colon volume, and less small bowel motility postprandially. They also showed positive associations between gastric volume and satiety scores, gastric emptying time and reflux scores, and small bowel motility and constipation scores. No differences in gastric emptying were observed. Small bowel volume and motility were used as inputs to a classification tool that separated patients and controls with 76% accuracy. In this work, we studied structural and functional differences between patients with diabetes and GI symptoms and healthy controls and observed differences in stomach, small bowel, and colon volumes, as well as an adynamic small bowel in patients with diabetes and GI symptoms. Associations between recorded parameters and perceived symptoms were also explored and discussed.
10.3390/jcm12185968
Magnetic Resonance Imaging of Gastric Motility in Conscious Rats.
bioRxiv : the preprint server for biology
Introduction:Gastrointestinal (GI) magnetic resonance imaging (MRI) can simultaneously capture gastric peristalsis, emptying, and intestinal filling and transit. Performing GI MRI with animals requires anesthesia, which complicates physiology and confounds interpretation and translation from animals to humans. This study aims to enable MRI in conscious rats, and for the first time, characterize GI motor functions in awake versus anesthetized conditions. Methods:We acclimated rats to remain awake, still, and minimally stressed during MRI. We scanned 14 Sprague-Dawley rats in both awake and anesthetized conditions after voluntarily consuming a contrast-enhanced test meal. Results:Awake rats remained physiologically stable during MRI, showed gastric emptying of 23.7±1.4% after 48 minutes, and exhibited strong peristaltic contractions propagating through the antrum with a velocity of 0.72±0.04 mm/s, a relative amplitude of 40.7±2.3%, and a frequency of 5.1±0.1 cycles per minute. In the anesthetized condition, gastric emptying was about half of that in the awake condition, likely due to the effect of anesthesia in halving the amplitudes of peristaltic contractions rather than their frequency (not significantly changed) or velocity. In awake rats, the intestine filled more quickly and propulsive contractions were more occlusive. Conclusion:We demonstrated the effective acquisition and analysis of GI MRI in awake rats. Awake rats show faster gastric emptying, stronger gastric contraction with a faster propagation speed, and more effective intestinal filling and transit, compared to anesthetized rats. Our protocol is expected to benefit future preclinical studies of GI physiology and pathophysiology.
10.1101/2024.09.09.612090
Validation of a rapid, semiautomatic image analysis tool for measurement of gastric accommodation and emptying by magnetic resonance imaging.
Banerjee Sreerup,Dixit Sudeepa,Fox Mark,Pal Anupam
American journal of physiology. Gastrointestinal and liver physiology
Magnetic resonance imaging (MRI) has advantages for the assessment of gastrointestinal structures and functions; however, processing MRI data is time consuming and this has limited uptake to a few specialist centers. This study introduces a semiautomatic image processing system for rapid analysis of gastrointestinal MRI. For assessment of simpler regions of interest (ROI) such as the stomach, the system generates virtual images along arbitrary planes that intersect the ROI edges in the original images. This generates seed points that are joined automatically to form contours on each adjacent two-dimensional image and reconstructed in three dimensions (3D). An alternative thresholding approach is available for rapid assessment of complex structures like the small intestine. For assessment of dynamic gastrointestinal function, such as gastric accommodation and emptying, the initial 3D reconstruction is used as reference to process adjacent image stacks automatically. This generates four-dimensional (4D) reconstructions of dynamic volume change over time. Compared with manual processing, this semiautomatic system reduced the user input required to analyze a MRI gastric emptying study (estimated 100 vs. 10,000 mouse clicks). This analysis was not subject to variation in volume measurements seen between three human observers. In conclusion, the image processing platform presented processed large volumes of MRI data, such as that produced by gastric accommodation and emptying studies, with minimal user input. 3D and 4D reconstructions of the stomach and, potentially, other gastrointestinal organs are produced faster and more accurately than manual methods. This system will facilitate the application of MRI in gastrointestinal research and clinical practice.
10.1152/ajpgi.00095.2014
A Novel Method for Time-Dependent Numerical Modeling of Gastric Motility Directly from Magnetic Resonance Imaging
Hosseini Saeed,Avci Recep,Paskaranandavadivel Nira,Palmada Nadun,Suresh Vinod,Cheng Leo K
Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference
Gastric motility has a critical role in disintegration and mixing of the ingested food inside the stomach. Several studies have been conducted to quantify and analyze the effect of the contractions of gastric musculature on the stomach contents. Despite the anatomical variation in stomach shape and motility patterns, previous numerical studies employed generalized geometries of the stomach as the computational domain for simulations. To model realistic gastric muscular contractions, the variation in stomach geometries need to be accounted for in numerical simulations. In the current study, a novel method was developed to utilize the recent advances in magnetic resonance imaging (MRI) technology and computational power expansion to build anatomically and physiologically realistic subject specific models of human gastric motility. In this method, MRI scans of the stomach were used to construct two and three dimensional geometry models of gastric motility. MRI was performed on 4 healthy participants. Using the developed method, dynamic numerical geometry models of gastric motility for each participant were constructed and related geometrical calculations were presented. Different combinations of solid and liquid test meals were consumed prior to the scans. The volume of the stomach ranged between 0.36 - 1.10 L in the fed state. The stomach models had an average length of 184 to 226 mm and a maximum diameter of 65 to 102 mm. Contraction propagation speed calculated from the models and MRI data were in good agreement, measuring around 2 mm/s.Clinical relevance- Clinicians can benefit from the proposed method for diagnostic purposes as the method is semi-automatic and can provide dynamic three-dimensional visualization of gastric motility of patients.
10.1109/EMBC44109.2020.9175607
Gastric motility and emptying assessment by magnetic resonance imaging after lung transplantation: correlation with gastric emptying scintigraphy.
Hayakawa Nobuyuki,Nakamoto Yuji,Chen-Yoshikawa Toyofumi F,Kido Aki,Ishimori Takayoshi,Fujimoto Koji,Yamada Tetsu,Sato Masaaki,Aoyama Akihiro,Date Hiroshi,Togashi Kaori
Abdominal radiology (New York)
PURPOSE:Gastroparesis is a frequent gastrointestinal complication after lung transplantation. Although gastric emptying scintigraphy (GES) is the standard technique to evaluate gastroparesis, magnetic resonance imaging (MRI) can also assess gastric motility and emptying. This study compared the results obtained by these two modalities. METHODS:Twenty-two lung transplant recipients underwent MRI and GES after ingesting a small pancake as a test meal. Parameters assessed on MRI included antral peristaltic wave velocity and frequency, and the ratios of gastric content volume at 15 and 35 min. GES parameters included retention rates (RR) in the stomach at 30, 60, and 120 min (RR30, RR60, and RR120) and half-time of emptying (T1/2) calculated by exponential curve fitting. Correlations between MRI and GES results were evaluated. RESULTS:Peristaltic wave velocity showed significant moderate negative correlations with RR120 (r = - 0.58, p < 0.05) and T1/2 (r = - 0.60, p < 0.05), indicating an association between reduced velocity and prolonged gastric emptying. Gastric content volume ratios on MRI showed significant moderate positive correlations with RR30 (r = 0.46, p < 0.05), RR60 (r = 0.60, p < 0.01), and T1/2 (r = 0.60, p < 0.01). There were no significant correlations between peristaltic wave frequency and GES parameters. MRI and GES parameters did not differ significantly between the six patients with and the 16 without upper gastrointestinal symptoms. CONCLUSIONS:MRI-based determinations of gastric motility and gastric emptying correlate with GES-based gastric emptying in lung transplant recipients, suggesting that MRI is useful for evaluating patients with gastroparesis.
10.1007/s00261-016-0959-5
A magnetic resonance imaging study of gastric motor function in patients with dyspepsia associated with Ehlers-Danlos Syndrome-Hypermobility Type: A feasibility study.
Menys A,Keszthelyi D,Fitzke H,Fikree A,Atkinson D,Aziz Q,Taylor S A
Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society
BACKGROUND:The clinical use of Magnetic Resonance Imaging (MRI) for investigating gastric motor function in dyspepsia is limited, largely due to protocol complexity, cost and limited availability. In this study, we explore the feasibility of a sub 60-minute protocol using a water challenge to assess gastric emptying, motility and accommodation in a cohort of Ehlers-Danlos Syndrome-Hypermobility type (EDS-HT) patients presenting with dyspepsia. METHODS:Nine EDS-HT patients (mean age 33, range: 26-50 all female) with a history of dyspepsia were recruited together with nine-matched controls. Subjects fasted for 6 hours prior to MRI. A baseline anatomical and motility scan was performed after which the subjects ingested 300 mL water. The anatomical and motility scans were then repeated every 10 minutes to a total of 60 minutes. Gastric emptying time, motility, and accommodation were calculated based on the observations of two observers for each EDS-HT subject and compared to their matched control using paired statistics. KEY RESULTS:Median motility increase following the water challenge was lower in EDS-HT subjects (11%, range: 0%-22%) compared to controls (22%, range: 13%-56%), P=.03. Median gastric emptying time was non-significantly decreased in EDS-HT subjects (12.5 minutes, range: 6-27) compared to controls (20 minutes, range: 7-30), P=.15. Accommodation was non-significantly reduced in EDS-HT subjects (56% increase, range: 32%-78%) compared to healthy controls (67% increase, range: 52%-78%), P=.19. CONCLUSIONS & INFERENCES:This study demonstrates the feasibility of a water challenge MRI protocol to evaluate gastric physiology in the clinical setting. Motility differences between EDS-HT and controls are worthy of further investigation.
10.1111/nmo.13090
Magnetic resonance imaging as a non-invasive tool to assess gastric emptying in mice.
Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society
BACKGROUND:Methods to study gastric emptying in rodents are time consuming or terminal, preventing repetitive assessment in the same animal. Magnetic resonance imaging (MRI) is a non-invasive technique increasingly used to investigate gastrointestinal function devoid of these shortcomings. Here, we evaluated MRI to measure gastric emptying in control animals and in two different models of gastroparesis. METHODS:Mice were scanned using a 9.4 Tesla MR scanner. Gastric volume was measured by delineating the stomach lumen area. Control mice were scanned every 30 min after ingestion of a 0.2 g meal and stomach volume was quantified. The ability of MRI to detect delayed gastric emptying was evaluated in models of morphine-induced gastroparesis and streptozotocin-induced diabetes. KEY RESULTS:Magnetic resonance imaging reproducibly detected increased gastric volume following ingestion of a standard meal and progressively decreased with a half emptying time of 59 ± 5 min. Morphine significantly increased gastric volume measured at t = 120 min (saline: 20 ± 2 vs morphine: 34 ± 5 mm ; n = 8-10; p < 0.001) and increased half emptying time using the breath test (saline: 85 ± 22 vs morphine: 161 ± 46 min; n = 10; p < 0.001). In diabetic mice, gastric volume assessed by MRI at t = 60 min (control: 23 ± 2 mm ; n = 14 vs diabetic: 26 ± 5 mm ; n = 18; p = 0.014) but not at t = 120 min (control: 21 ± 3 mm ; n = 13 vs diabetic: 18 ± 5 mm ; n = 18; p = 0.115) was significantly increased compared to nondiabetic mice. CONCLUSIONS AND INFERENCES:Our data indicate that MRI is a reliable and reproducible tool to assess gastric emptying in mice and represents a useful technique to study gastroparesis in disease models or for evaluation of pharmacological compounds.
10.1111/nmo.14490
Contrast-Enhanced Magnetic Resonance Imaging of Gastric Emptying and Motility in Rats.
Lu Kun-Han,Cao Jiayue,Oleson Steven Thomas,Powley Terry L,Liu Zhongming
IEEE transactions on bio-medical engineering
The assessment of gastric emptying and motility in humans and animals typically requires radioactive imaging or invasive measurements. Here, we developed a robust strategy to image and characterize gastric emptying and motility in rats based on contrast-enhanced magnetic resonance imaging (MRI) and computer-assisted image processing. The animals were trained to naturally consume a gadolinium-labeled dietgel while bypassing any need for oral gavage. Following this test meal, the animals were scanned under low-dose anesthesia for high-resolution T1-weighted MRI in 7 Tesla, visualizing the time-varying distribution of the meal with greatly enhanced contrast against non-gastrointestinal (GI) tissues. Such contrast-enhanced images not only depicted the gastric anatomy, but also captured and quantified stomach emptying, intestinal filling, antral contraction, and intestinal absorption with fully automated image processing. Over four postingestion hours, the stomach emptied by 27%, largely attributed to the emptying of the forestomach rather than the corpus and the antrum, and most notable during the first 30 min. Stomach emptying was accompanied by intestinal filling for the first 2 h, whereas afterward intestinal absorption was observable as cumulative contrast enhancement in the renal medulla. The antral contraction was captured as a peristaltic wave propagating from the proximal to distal antrum. The frequency, velocity, and amplitude of the antral contraction were on average 6.34 ± 0.07 contractions per minute, 0.67 ± 0.01 mm/s, and 30.58 ± 1.03%, respectively. These results demonstrate an optimized MRI-based strategy to assess gastric emptying and motility in healthy rats, paving the way for using this technique to understand GI diseases, or test new therapeutics in rat models.The assessment of gastric emptying and motility in humans and animals typically requires radioactive imaging or invasive measurements. Here, we developed a robust strategy to image and characterize gastric emptying and motility in rats based on contrast-enhanced magnetic resonance imaging (MRI) and computer-assisted image processing. The animals were trained to naturally consume a gadolinium-labeled dietgel while bypassing any need for oral gavage. Following this test meal, the animals were scanned under low-dose anesthesia for high-resolution T1-weighted MRI in 7 Tesla, visualizing the time-varying distribution of the meal with greatly enhanced contrast against non-gastrointestinal (GI) tissues. Such contrast-enhanced images not only depicted the gastric anatomy, but also captured and quantified stomach emptying, intestinal filling, antral contraction, and intestinal absorption with fully automated image processing. Over four postingestion hours, the stomach emptied by 27%, largely attributed to the emptying of the forestomach rather than the corpus and the antrum, and most notable during the first 30 min. Stomach emptying was accompanied by intestinal filling for the first 2 h, whereas afterward intestinal absorption was observable as cumulative contrast enhancement in the renal medulla. The antral contraction was captured as a peristaltic wave propagating from the proximal to distal antrum. The frequency, velocity, and amplitude of the antral contraction were on average 6.34 ± 0.07 contractions per minute, 0.67 ± 0.01 mm/s, and 30.58 ± 1.03%, respectively. These results demonstrate an optimized MRI-based strategy to assess gastric emptying and motility in healthy rats, paving the way for using this technique to understand GI diseases, or test new therapeutics in rat models.
10.1109/TBME.2017.2737559
Quantification of gastric emptying with magnetic resonance imaging in healthy volunteers: A systematic review.
Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society
BACKGROUND:Several magnetic resonance imaging (MRI) protocols have been used to assess gastric emptying (GE) with MRI. This systematic review summarizes the current literature on the topic. The aim was to provide an overview of the available imaging protocols and underline the items that appear most agreed upon and those that deserve further investigation. METHODS:According to PRISMA guidelines, two independent reviewers conducted a systematic literature search with a pre-specified strategy in different databases. Peer-reviewed articles that utilized MRI techniques to assess GE in healthy volunteers (HVs) were included. The quality and the outcomes of the studies were reported and analyzed. KEY RESULTS:The literature search yielded 30 studies (531 HVs, weighted mean age 27.4, weighted mean body mass index 23.0 kg/m ), T2-weighted sequences, balanced turbo field echo, and balanced gradient echo were evenly utilized, with volunteers in the supine position (74% of the studies). After overnight fasting, both liquid (56%) and mixed (44%) meals were equally utilized. Segmentation of the volumes was predominantly performed manually (63%) with a reported mean T50 ranging from 7 to 330 min. CONCLUSIONS & INFERENCES:As observed in this systematic review, MRI is a flexible tool for assessing GE. Different protocols were analyzed, showing an equal capacity to assess the GE. However, many items in these protocols still require further investigation to obtain a common standard and increase this assessment quality.
10.1111/nmo.14371