Activation induced changes in GABA: functional MRS at 7 T with MEGA-sLASER

Functional magnetic resonance spectroscopy (fMRS) has been used to assess the dynamic metabolic responses of the brain to a physiological stimulus non-invasively. However, only limited information on the dynamic functional response of γ-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the brain, is available. We aimed to measure the activation-induced changes in GABA unambiguously using a spectral editing method, instead of the conventional direct detection techniques used in previous fMRS studies. The Mescher-Garwood-semi-localised by adiabatic selective refocusing (MEGA-sLASER) sequence was developed at 7 T to obtain the time course of GABA concentration without macromolecular contamination. A significant decrease (−12±5%) in the GABA to total creatine ratio (GABA/tCr) was observed in the motor cortex during a period of 10 minutes of hand-clenching, compared to an initial baseline level (GABA/tCr = 0.11±0.02) at rest. An increase in the Glx (glutamate and glutamine) to tCr ratio was also found, which is in agreement with previous findings. In contrast, no significant changes in NAA/tCr and tCr were detected. With consistent and highly efficient editing performance for GABA detection and the advantage of visually identifying GABA resonances in the spectra, MEGA-sLASER is demonstrated to be an effective method for studying of dynamic changes in GABA at 7 T

Delayed gastric emptying and reduced postprandial small bowel water content of equicaloric whole meal bread versus rice meals in healthy subjects: novel MRI insights

BACKGROUND/OBJECTIVES: Postprandial bloating is a common symptom in patients with functional gastrointestinal (GI) diseases. Whole meal bread (WMB) often aggravates such symptoms though the mechanisms are unclear. We used magnetic resonance imaging (MRI) to monitor the intragastric fate of a WMB meal (11% bran) compared to a rice pudding (RP) meal. SUBJECTS/METHODS: 12 healthy volunteers completed this randomised crossover study. They fasted overnight and after an initial MRI scan consumed a glass of orange juice with a 2267 kJ WMB or an equicaloric RP meal. Subjects underwent serial MRI scans every 45 min up to 270 min to assess gastric volumes and small bowel water content and completed a GI symptom questionnaire. RESULTS: The MRI intragastric appearance of the two meals was markedly different. The WMB meal formed a homogeneous dark bolus with brighter liquid signal surrounding it. The RP meal separated into an upper, liquid layer and a lower particulate layer allowing more rapid emptying of the liquid compared to solid phase (sieving). The WMB meal had longer gastric half emptying times (132±8 min) compared to the RP meal (104±7 min), P<0.008. The WMB meal was associated with markedly reduced MRI-visible small bowel free mobile water content compared to the RP meal, P<0.0001. CONCLUSIONS: WMB bread forms a homogeneous bolus in the stomach which inhibits gastric sieving and hence empties slower than the equicaloric rice meal. These properties may explain why wheat causes postprandial bloating and could be exploited to design foods which prolong satiation

Dual registration of abdominal motion for motility assessment in free-breathing data sets acquired using dynamic MRI.

At present, registration-based quantification of bowel motility from dynamic MRI is limited to breath-hold studies. Here we validate a dual-registration technique robust to respiratory motion for the assessment of small bowel and colonic motility. Small bowel datasets were acquired in breath-hold and free-breathing in 20 healthy individuals. A pre-processing step using an iterative registration of the low rank component of the data was applied to remove respiratory motion from the free breathing data. Motility was then quantified with an existing optic-flow (OF) based registration technique to form a dual-stage approach, termed Dual Registration of Abdominal Motion (DRAM). The benefit of respiratory motion correction was assessed by (1) assessing the fidelity of automatically propagated segmental regions of interest (ROIs) in the small bowel and colon and (2) comparing parametric motility maps to a breath-hold ground truth. DRAM demonstrated an improved ability to propagate ROIs through free-breathing small bowel and colonic motility data, with median error decreased by 90% and 55%, respectively. Comparison between global parametric maps showed high concordance between breath-hold data and free-breathing DRAM. Quantification of segmental and global motility in dynamic MR data is more accurate and robust to respiration when using the DRAM approach

Mechanisms underlying the laxative effect of lactulose: A randomized placebo‐controlled trial showing increased small bowel water and motility unaltered by the 5‐HT3 receptor antagonist, ondansetron

Background: Lactulose is a laxative which accelerates transit and softens stool. Our aim was to investigate its mechanism of action and use this model of diarrhea to investigate the anti-diarrheal actions of ondansetron. Methods: A double-blind, randomized, placebo-controlled crossover study of the effect of ondansetron 8 mg in 16 healthy volunteers. Serial MRI scans were performed fasted and 6 h after a meal. Participants then received lactulose 13.6 g twice daily and study drug for a further 36 h. On Day 3, they had further serial MRI scans for 4 h. Measurements included small bowel water content (SBWC), colonic volume, colonic gas, small bowel motility, whole gut transit, and ascending colon relaxation time (T1AC), a measure of colonic water content. Key Results: Lactulose increased area under the curve (AUC) of SBWC from 0 to 240 min, mean difference 14.2 L · min (95% CI 4.1, 24.3), p = 0.009, and substantially increased small bowel motility after 4 h (mean (95% CI) 523 (457–646) a.u. to 852 (771–1178) a.u., p = 0.007). There were no changes in T1AC after 36 h treatment. Ondansetron did not significantly alter SBWC, small bowel motility, transit, colonic volumes, colonic gas nor T1AC, with or without lactulose. Conclusion & Inferences: Lactulose increases SBWC and stimulates small bowel motility; however, unexpectedly it did not significantly alter colonic water content, suggesting its laxative effect is not osmotic but due to stimulation of motility. Ondansetron's lack of effect on intestinal water suggests its anti-diarrheal effect is not due to inhibition of secretion but more likely altered colonic motility

Stimulation of colonic motility by oral PEG electrolyte bowel preparation assessed by MRI : comparison of split vs single dose

Peer reviewe

Glycemic, Gastrointestinal, Hormonal and Appetitive Responses to Pearl Millet or Oats Porridge Breakfasts: a Randomized, Crossover Trial in Healthy Humans

Whole grain cereal breakfast consumption has been associated with beneficial effects on glucose and insulin metabolism as well as satiety. Pearl millet is a popular ancient grain variety that can be grown in hot, dry regions. However, little is known about its health effects. This study investigated the effect of a pearl millet porridge (PMP) compared with a well-known Scottish oats porridge (SOP) on glycaemic, gastrointestinal, hormonal and appetitive responses. In a randomized, two way crossover trial, 26 healthy participants consumed two iso-energetic/volumetric PMP or SOP breakfast meals, served with a drink of water. Blood samples for glucose, insulin, GLP-1, GIP and PYY, gastric volumes and appetite ratings were collected for two hours postprandially, followed by an ad libitum meal and food intake records for the remainder of the day. The incremental area under the curve (iAUC2h) for blood glucose was not significantly different between the porridges (p ˃ 0.05). The iAUC2h gastric volume was larger for PMP compared with SOP (p = 0.045). The iAUC2h GIP concentration was significantly lower for PMP compared with SOP (p = 0.001). Other hormones and appetite responses were similar between meals. In conclusion, this study reports, for the first time, data on glycaemic and physiological responses to a pearl millet breakfast, showing that this ancient grain could represent a sustainable, alternative, with health-promoting characteristics comparable to oats. GIP is an incretin hormone linked to triacylglycerol absorption in adipose tissue, therefore the lower GIP response for PMP may be an added health benefit

Assessing the impact of posture on diaphragm morphology and function using an open upright MRI system – a pilot study

PurposeThe diaphragm is the most important muscle of respiration. Disorders of the diaphragm can have a deleterious impact on respiratory function. We aimed to evaluate the use of an open-configuration upright low-field MRI system to assess diaphragm morphology and function in patients with bilateral diaphragm weakness (BDW) and chronic obstructive pulmonary disease (COPD) with hyperinflation.MethodThe study was approved by the National Research Ethics Committee, and written consent was obtained. We recruited 20 healthy adult volunteers, six subjects with BDW, and five subjects with COPD with hyperinflation. We measured their vital capacity in the upright and supine position, after which they were scanned on the 0.5 T MRI system during 10-second breath-holds at end-expiration and end-inspiration in both positions. We developed and applied image analysis methods to measure the volume under the dome, maximum excursion of hemidiaphragms, and anterior-posterior and left-right extension of the diaphragm.ResultsAll participants were able to complete the scanning protocol. The patients found scanning in the upright position more comfortable than the supine position. All differences in the supine inspiratory-expiratory parameters, excluding left-right extension, were significantly smaller in the BDW and COPD groups compared with healthy volunteers. No significant correlation was found between the postural change in diaphragm morphology and vital capacity in either group.ConclusionOur combined upright-supine MR imaging approach facilitates the assessment of the impact of posture on diaphragm morphology and function in patients with BDW and those with COPD with hyperinflation

intravoxel incoherent motion measurements in the human placenta using echo-planar imaging at 0.5

This paper presents the first in vivo measurements of intravoxel incoherent motion in the human placenta, obtained using the pulsed gradient spin echo (PGSE) sequence. The aims of this study were two-fold. The first was to provide an initial estimate of the values of the IVIM parameters in this organ, which are currently unknown. The second aim was then to use these results to optimize the sequence timings for future studies