Gastric Emptying Validation Pilot Study (MRI Val)

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.

Inclusion criteria

• Healthy (health status will be confirmed at screening).
• Able to fully comprehend the informed consent process and give informed consent.
• BMI <30 kg/m2

Exclusion criteria

• Known contraindication to MRI scanning (for example, pacemaker/implanted defibrillator, aneurysm clips, implanted programmable device, intra-ocular metallic fragment, claustrophobia)
• Major psychiatric, cognitive or mood disorder.
• Any other significant chronic medical conditions, including diabetes (type 1 and 2), asthma and epilepsy.
• Any acute major illness or surgery within one year prior to participation.
• Glucose intolerance (as assessed by a finger-prick test at screening).
• Having taken part in a research study in the last 3 months involving invasive procedures, ionising radiation or an inconvenience allowance.