Effects of gastrointestinal tissue structure on computed dipole vectors
Effects of gastrointestinal tissue structure on computed dipole vectors
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DOI：
10.1186/1475-925x-6-39
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发表时间：
2007-10-22
影响因子：
3.9
通讯作者：
Cheng, Leo K.
中科院分区：
文献类型：
--
作者：
Austin, Travis M.;Li, Liren;Cheng, Leo K.
背景：消化系统疾病很难在不使用侵入性测量的情况下进行评估。对潜在胃肠道活动引起的身体表面电和磁活动的非侵入性测量并未广泛使用，主要是由于其难以解释。基本过程的数学模型可能有助于提供更多的信息。在对肌电活动建模时，电场通常由等效偶极子源表示。胃肠系统由平滑肌（SM）细胞和卡哈尔间质细胞（ICC）的交替层组成。此外，小肠具有高曲率区域，因为肠向后弯曲。最终使用建模诊断，我们必须提高我们的理解，肠结构上的偶极子vector behaviors.Methods的效果：正常的肠电行为模拟简单的几何形状，使用单域制定。然后用偶极子矢量表示肌电场，并对结构的影响进行了检查。将3D肠模型与计算效率更高的ID表示进行比较，以确定所得偶极向量的差异。此外，电导率值和不同肌肉层的厚度在3D模型和偶极子vectors.Results上的影响是不同的：偶极子矢量的方向在很大程度上受曲率和由SM和ICC层的不同属性所造成的电波前的跨壁梯度。这种梯度导致偶极子与电传播的主要方向成一定角度。当纵、环肌比例增大或肌层沿着和跨层传导率增大时，该角度增大。ID模型能够表示小肠的几何形状，并成功捕获了慢波沿网格长度的传播，但是，它无法表示每层内的透壁扩散，这意味着与完整的3D模型相比，等效偶极子源缺少横向分量，幅度降低。肠壁的结构影响通过壁的电位梯度和偶极子矢量的方向和大小。我们已经看到，具有对称壁结构和极端各向异性电导率的模型在偶极幅度和方向上与ID模型具有相似的特征。如果使用有效的ID模型而不是3D模型，则需要考虑幅度和方向的差异。
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 ID 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 ID 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 ID model. If efficient ID models are used instead of 3D models, then both the differences in magnitude and orientation need to be accounted for.