Gastric Emptying Validation Pilot Study (MRI Val)
Condition: Gastrointestinal Dysfunction
Study type: Observational

Summary: 
      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.
    

Detailed description: 
      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.
    

Intervention name(s): Oral glucose tolerance test
Intervention type(s): Diagnostic Test
Intervention description(s): A drink containing 75g of glucose together with 150mg carbon-13 sodium acetate in 300ml water
Observational model: Cohort
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Healthy male and female adults
      
Keywords: gastric emptying; Magnetic resonance imaging; '13-C acetate' breath test