Applied potential tomography: a new non-invasive technique for assessing gastric function

Applied potential tomography is a new, non-invasive technique that yields sequential images of the resistivity of gastric contents after subjects have ingested a liquid or semi-solid meal. This study validates the technique as a means of measuring gastric emptying. Experiments in vitro showed an excellent correlation between measurements of resistivity and either the square of the radius of a glass rod or the volume of water in a spherical balloon when both were placed in an oval tank containing saline. Altering the lateral position of the rod in the tank did not alter the values obtained. Images of abdominal resistivity were also directly correlated with the volume of air in a gastric balloon. Profiles of gastric emptying of liquid meals obtained using APT were very similar to those obtained using scintigraphy or dye dilution techniques provided that acid secretion was inhibited by cimetidine. Profiles of emptying of a mashed potato meal using APT were also very similar to those obtained by scintigraphy. Measurements of the emptying of a liquid meal from the stomach were reproducible if acid secretion was inhibited by cimetidine. Thus, APT is an accurate and reproducible method of measuring gastric emptying of liquids and particulate food. It is inexpensive, well tolerated, easy to use and ideally suited for multiple studies in patients, even those who are pregnant. A preliminary study is also presented that assesses the technique as a means of measuring gastric acid secretion. Comparison of resistivity changes with measured acid secretion following the injection of pentagastrin shows good correlations. APT might offer a non-invasive alternative to the use of a nasogastric tube and acid collection.