ABSTRACT
Electrical impedance tomography (EIT) is a tubeless technique that generates tomographic images of gastric resistivity. We investigated the application of EIT to measure gastric acid secretion. Nineteen normal subjects underwent a standard intubation test. Basal acid output (BAO) and stimulated acid output (SAO) (millimoles per hour) were measured before and after pentagastrin, respectively. On a different day, EIT was performed before (basal) and after pentagastrin (stimulated). The changes in impedance over time were measured and the area under the curve (AUC) was calculated. Both the tests were repeated in 13 subjects after omeprazole treatment. As in the intubation test, there was the expected increase in AUC value after pentagastrin (basal vs stimulated; 1.2 +/- 2.8 vs 731 +/- 297, P < 0.0001). A significant fall in acid output and AUC following omeprazole pretreatment was observed (without vs with omeprazole; 20.5 +/- 5.7 vs 0.03 +/- 0.06, P < 0.0001 for intubation test and 731 +/- 297 vs 44 +/- 172, P < 0.0001 for EIT). There was a significant correlation between SAO and the delta AUC with (r = 0.65 P < 0.001) or without (r = 0.95, P < 0.001) omeprazole and in all the experiments (r = 0.87, P < 0.001). This study demonstrates the predictable change of gastric impedance and may be useful as a noninvasive test for measuring gastric acid secretion.
Subject(s)
Electric Impedance , Gastric Acid/metabolism , Tomography , Adolescent , Adult , Anti-Ulcer Agents/pharmacology , Humans , Omeprazole/pharmacology , Pentagastrin/pharmacology , Predictive Value of Tests , Reference Values , Sensitivity and SpecificityABSTRACT
Electrical impedance tomography (EIT) is designed essentially for two-dimensional imaging, but current flow in the third dimension causes images to be formed for objects in 3D. The present work has shown that the image of an object is shifted in position towards the centre almost linearly with the 3D distance from the electrode plane and that the slope of this linear variation depends on the radial distance of the object. An empirical curve has been fitted to this dependence, based on which a method has been developed to locate 3D point objects from EIT measurements in only two planes. This will be useful in clinical and other applications in which 3D objects are few and widely separated. This new methodology may be the basis for 3D imaging in the future.
