Intragastric movement assessment by measuring magnetic field decay of magnetised tracer particles in a solid meal

Abstract

The aim of the study is to evaluate and further develop a non-invasive method for the measurement of intragastric movements. Ferrimagnetic particles (gamma-Fe2O3) are ingested within a standard test meal (pancakes), and given a permanent magnetisation by an applied homogeneous magnetic field. Magnetic measurements are performed outside the stomach, using fluxgate magnetometers anterior and posterior, in seven periods of 12 minutes each. Any movements caused by grinding and mixing in the ingesta would result in a misalignment of the magnetic moments, and hence in a decay of the external magnetic field. Twelve healthy male volunteers, aged 26.7 +/- 2.7 years (mean +/- SD), are studied. After an initial phase of low and almost linear flux density decay (32 +/- 19%, from minute 10 to minute 22 postprandially), the mean rotation and decay gradually increases (67 +/- 21%, from minute 100 to 112), and the decay becomes bi-exponential. It is hypothesised that the bi-exponential nature of the decay corresponds to the relative fractions, solid and semifluid, of gastric content. The decay curves often show superimposed 3 cycles min-1 variations, which correlate well with the basic electrical rhythm of the stomach measured by electrogastrography (EGG). It is concluded that these variations are induced by gastric contractions.

Implementation of a Magnetic Stimulator to Study the Human Stomach Activity

“…It is important to point out that these results are consistent with previous results reported in different works [2,3,4] Recording 40 min after the contrast was swallowed CONCLUSIONS Using a magnetic stimulator and a fluxgate device in combination with magnetite as oral contrast, is possible to quantify the mechanical activity of the stomach, estimate the relaxation constant and measure the magnitude of the signals. These three parameters are associated with peristaltic frequency, gastric motility, and gastric emptying, respectively.…”

“…So that, testing techniques to study GI system that minimize deleterious effects, avoid invading the patient privacy and are available at a small cost, are necessary. One of them is the Biomagnetism technique, whom has showed potentiality in GI studies in the last years [1][2][3][4]. Ionic movements or any oral magnetic contrast as a magnetic source are used in this technique.…”

“…Ionic movements or any oral magnetic contrast as a magnetic source are used in this technique. A SQUID magnetometer is used for recording the signal in the first case, while a magnetic stimulator (MS) and a fluxgate sensor can be implemented in the second case [2][3][4]. One of the two biomagnetic modality has to be considered on this kind of studies.…”

“…In this work, the last one was used. A magnetic stimulator was implemented, magnetite (Fe3O4) diluted in yogurt, as a magnetic oral contrast and fluxgate magnetometer were used [2][3][4].…”

Spatiotemporal evaluation of human colon motility using three-axis fluxgates and magnetic markers

“…Their main advantage is high stability with temperature, and their main disadvantages axe both their size and cost (RIPKA et al, 2001). They have been intensively used in GI system studies, mainly in combination with magnetic tracers (FORSMAN, 1998;2000;CARNEIRO et al, 1999). In this work, the combination of a portable magnetic probe and an MM was implemented to study the spatiotemporal mechanical activity of the human colon, in healthy subjects, where measurements of the contractile activity were taken.…”