Gastric Emptying Validation Pilot Study (MRI Val)

Overview

The primary aim of this study is to assess (in healthy volunteers) the rate at which a glucose drink leaves the stomach by sequential magnetic resonance imaging (MRI) of the stomach contents using a 0.5 tesla upright MRI scanner, and comparing with the rate derived from a standard method which uses a stable isotope tracer and breath testing. The main question it aims to answer are: * Do MRI derived images of stomach contents at low magnetic field (0.5 Tesla) have sufficient resolution to provide a reproducible assessment of gastric emptying * What is the agreement and relationship between the rate of gastric emptying determined from the 2 methods Participants will be asked to attend the imaging centre on one occasion in the morning after fasting from midnight and to sit within an upright MRI scanner for a period of approximately 140 minutes. Images of their stomach will be taken before and for 2 hours after consuming a drink containing glucose and a small amount of sodium acetate which contains a heavier form of carbon. Before each image is taken, participants will be asked to exhale into a 500ml bag to collect a breath sample.

The rate at which food empties from the stomach is a key assessment made in appetite and metabolic research, as well as studies investigating gastrointestinal function in health and disease. This assessment can be achieved by measuring the volume of the stomach contents at timepoints after eating using magnetic resonance imaging (MRI) and calculating the gastric emptying rate from the decrease in volume which occurs over time. However, these measures are traditionally made when the individual is lying supine within the bore of the MRI machine and this postural position may impact the rate that food empties from the stomach. A low-field 0.5 Tesla 'upright' MRI scanner could address the problem of measuring gastric emptying rate when supine. However, the resolution of the images obtained are poorer than those obtained at higher field strengths (e.g. at 3 Tesla). The primary aim of this study is to compare gastric emptying kinetics assessed by sequential MR imaging of the stomach with a standard method which uses a stable isotope tracer (13-Carbon labelled sodium acetate) and breath testing. Twelve healthy, non-obese volunteers (18 to 60 years old) will attend the imaging centre on one occasion in the morning after fasting from midnight and sit within an upright MRI scanner for a period of approximately 140 minutes. Images of their stomach will be taken before and every 5 minutes for 1 hour, and every 10 minutes for the following hour, after consuming a drink containing glucose and 150mg of sodium acetate which contains a heavier (non-radioactive) form of carbon (carbon-13). Before each image is taken, participants will exhale into a 500ml bag to enable a breath sample to be collected. Breath samples will subsequently be analysed for carbon-13 enrichment of expired carbon dioxide (CO2) using mass spectrometry.