Computer simulation of the impact of different ... - Springer Link

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Computer simulation of the impact of different dimensions of the stomach on the validity of electrogastrograms M, P. Mintchev 2

K . L . Bowes 1

Departments of 1Surgery, University of Alberta, Edmonton and 2Electrical Engineering, University of Calgary, Alberta, Canada T2N 1N4 AbstractmThe impact of the dimensions of the stomach on cutaneous recordings of

gastric electrical activity (GEA) has not been adequately studied. The stomach was represented as a truncated conoid in a spherical coordinate system. The gastric electric field was modelled using a previously described methodology. Electrical potentials were calculated from sets of points simulating standard cutaneous recordings. The frequency of the signals was maintained at 3 cycles rain-~ (period of repetition: 20 s), while the velocity of propagation of the depolarisation waves was reduced relative to the reduction in gastric dimensions. The signals were digitally contaminated with a random artificial artefact with a constant amplitude range of 0.2mV, while the dimensions of the conoid (the circumferential radii and the length of the central axis) were decreased by factors of 1.5, two, four, six and eight. Simulated EGG signals were evaluated quantitatively. Simulated EGG records contaminated with random signals recorded from stomachs with decreasing dimensions exhibited non-linearly increasing standard deviations (p 0.45 cycles rain - I were qualified as abnormal according to the second criterion for normality (Fig. 2, Table I). However, the temporal and propagative organisation of GEA on the conoid itself was in fact perfectly normal (Fig. 3). Probability density functions calculated from the MF values of simulated EGGs recorded from stomach models with different dimensions showed a clear tendency to lose their normal distribution (Fig. 4).

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Medical & Biological Engineering & C o m p u t i n g

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