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Magnetoenterography (MENG) is a new, non-invasive technique that measures gastrointestinal magnetic signals near the body surface. This study was undertaken to evaluate the temporal and spatial characteristics of the magnetic signals generated by gastric and duodenal slow wave activity. The gastrointestinal magnetic fields of eight normal subjects were measured for 60 minutes in both the fasting and fed state using 36 magnetic sensors simultaneously. The results were displayed as a succession of maps over time showing the temporal evolution of the spatial distribution of the signal over the upper abdomen. In all subjects, slow wave activity of the stomach centred at 3.0 +/- 0.5 cycles min-1 in both the fasting and fed state was observed. The duodenal signal at 11.0 +/- 1.0 cycles min-1 was observed in four subjects. The spatial distribution of these two signals is distinctly different. The observed spatial and temporal variations are described in terms of a model used previously to explain the potentials observed in electrogastrography (EGG).

The magnetic-hyperfine-field distribution in amorphous Fe788&3Si9 is investigated.The present analysis shows a distribution which consists of a single peak arid is at odds with a recent report of a bimodal distribution. Recently, Bhatnagar and Ravi' have reported hyperfinefield distributions in the amorphous alloy Fe788i3Si9. Subsequently, Bhatnagar and co-workers have reported studies of amorphous Fe798t6Sis (Ref. 2) and Fest8$35Sl35C2 (Ref. 3) that have yielded similar results. For Fe788i3Si9 the Fe

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Aims To investigate the ability of spectral features of signal-averaged body-surface potential maps in identifying post-infarction patients who are at risk of developing ventricular tachycardia. Methods and ResultsWe recorded 120 lead body surface potential maps during sinus rhythm in 135 subjects (45 patients with healed myocardial infarction but no history of venticular tachycardia, 45 patients with both healed myocardial infarction and at least one episode of sustained ventricular tachycardia, and 45 normal subjects) and analysed spectral features of body surface potential maps selected on the basis of isoharmonic maps for given bands of the frequency spectrum. We found that in the lowfrequency band (1-11 Hertz), the group-mean power spectra of leads located at isoharmonic map maxima were significantly different (P<0·0001) between the two groups of myocardial infarction patients. We estimated that this single feature alone can prospectively identify myocardial infarction patients at risk for ventricular tachycardia with a predictive accuracy of 74 6%. ConclusionOur results suggest that the bulk of diagnostic information associated with arrhythmogenicity resides in the low-frequency band of the power spectrum. This finding is at variance with the established notion that only the high-frequency component of signal-averaged electrocardiograms carries such information.