Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA.
IEEE Trans Biomed Eng. 2013 Aug;60(8):2316-24. doi: 10.1109/TBME.2013.2256134. Epub 2013 Apr 1.
Conductance catheters are known to have a nonuniform spatial sensitivity due to the distribution of the electric field. The Geselowitz relation is applied to murine and multisegment conductance catheters using finite element models to determine the spatial sensitivity in a uniform medium and simplified left ventricle models. A new formulation is proposed that allows determination of the spatial sensitivity to admittance. Analysis of FEM numerical modeling results using the Geselowitz relation provides a true measure of parallel conductance in simplified left ventricle models for assessment of the admittance method and hypertonic saline techniques. The spatial sensitivity of blood conductance (Gb) is determined throughout the cardiac cycle. Gb is converted to volume using Wei's equation to determine if the presence of myocardium alters the nonlinear relationship through changes to the electric field. Results show that muscle conductance (Gm) from the admittance method matches results from the Geselowitz relation and that the relationship between Gb and volume is accurately fit using Wei's equation. Single-segment admittance measurements in large animals result in a more evenly distributed sensitivity to the LV blood pool. The hypertonic saline method overestimates parallel conductance throughout the cardiac cycle in both murine and multisegment conductance catheters.
电导导管由于电场的分布而具有非均匀的空间灵敏度。应用 Geselowitz 关系，使用有限元模型来确定均匀介质和简化左心室模型中的空间灵敏度。提出了一种新的公式，可以确定导纳的空间灵敏度。使用 Geselowitz 关系对 FEM 数值建模结果进行分析，为评估导纳法和高渗盐水技术的简化左心室模型中的并行电导提供了真正的测量方法。在整个心动周期中确定血液电导 (Gb) 的空间灵敏度。使用 Wei 方程将 Gb 转换为体积，以确定心肌的存在是否通过改变电场来改变非线性关系。结果表明，导纳法中的肌电导 (Gm) 与 Geselowitz 关系的结果相匹配，并且 Wei 方程可以准确拟合 Gb 与体积之间的关系。大型动物的单段导纳测量结果导致对 LV 血池的灵敏度分布更加均匀。高渗盐水法在整个心动周期中都会高估鼠和多段电导导管中的并行电导。
