Effects of gastrointestinal tissue structure on computed dipole vectors

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dc.contributor.author Austin, Travis en
dc.contributor.author Li, Liren en
dc.contributor.author Pullan, Andrew en
dc.contributor.author Cheng, Leo K en
dc.date.accessioned 2008-09-12T03:59:17Z en
dc.date.available 2008-09-12T03:59:17Z en
dc.date.issued 2007 en
dc.identifier.citation Biomedical Engineering Online 6(39):1-9 2007 en
dc.identifier.issn 1475-925X en
dc.identifier.uri http://hdl.handle.net/2292/2909 en
dc.description.abstract BACKGROUND:Digestive diseases are difficult to assess without using invasive measurements. Non-invasive measurements of body surface electrical and magnetic activity resulting from underlying gastro-intestinal activity are not widely used, in large due to their difficulty in interpretation. Mathematical modelling of the underlying processes may help provide additional information. When modelling myoelectrical activity, it is common for the electrical field to be represented by equivalent dipole sources. The gastrointestinal system is comprised of alternating layers of smooth muscle (SM) cells and Interstitial Cells of Cajal (ICC). In addition the small intestine has regions of high curvature as the intestine bends back upon itself. To eventually use modelling diagnostically, we must improve our understanding of the effect that intestinal structure has on dipole vector behaviour.METHODS:Normal intestine electrical behaviour was simulated on simple geometries using a monodomain formulation. The myoelectrical fields were then represented by their dipole vectors and an examination on the effect of structure was undertaken. The 3D intestine model was compared to a more computationally efficient 1D representation to determine the differences on the resultant dipole vectors. In addition, the conductivity values and the thickness of the different muscle layers were varied in the 3D model and the effects on the dipole vectors were investigated.RESULTS:The dipole vector orientations were largely affected by the curvature and by a transmural gradient in the electrical wavefront caused by the different properties of the SM and ICC layers. This gradient caused the dipoles to be oriented at an angle to the principal direction of electrical propagation. This angle increased when the ratio of the longitudinal and circular muscle was increased or when the the conductivity along and across the layers was increased. The 1D model was able to represent the geometry of the small intestine and successfully captured the propagation of the slow wave down the length of the mesh, however, it was unable to represent transmural diffusion within each layer, meaning the equivalent dipole sources were missing a lateral component and a reduced magnitude when compared to the full 3D models.CONCLUSION:The structure of the intestinal wall affected the potential gradient through the wall and the orientation and magnitude of the dipole vector. We have seen that the models with a symmetrical wall structure and extreme anisotropic conductivities had similar characteristics in their dipole magnitudes and orientations to the 1D model. If efficient 1D models are used instead of 3D models, then both the differences in magnitude and orientation need to be accounted for. en
dc.publisher BioMed Central Ltd en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. Details obtained from http://www.sherpa.ac.uk/romeo/issn/1475-925X/ en
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.rights.uri http://creativecommons.org/licenses/by-nc-sa/3.0/nz/ en
dc.source.uri http://dx.doi.org/10.1186/1475-925X-6-39 en
dc.title Effects of gastrointestinal tissue structure on computed dipole vectors en
dc.type Journal Article en
dc.subject.marsden Fields of Research::290000 Engineering and Technology::291500 Biomedical Engineering en
dc.identifier.doi 10.1186/1475-925X-6-39 en
dc.rights.holder Copyright: 2007 Austin et al; licensee BioMed Central Ltd. en
dc.rights.accessrights http://purl.org/eprint/accessRights/OpenAccess en
pubs.org-id ABI en

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