Analysis of electrode configurations for measuring cardiac tissue conductivities and fibre rotation
Analysis of electrode configurations for measuring cardiac tissue conductivities and fibre rotation
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DOI：
10.1007/s10439-006-9098-4
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发表时间：
2006-06-01
影响因子：
3.8
通讯作者：
Kilpatrick, David
中科院分区：
文献类型：
--
作者：
Johnston, Barbara M.;Johnston, Peter R.;Kilpatrick, David
本文介绍了一种可用于直接测量心脏组织参数的多电极网格。使用两遍过程，其中在动作电位的平台期在这些电极的子集上进行电位测量，并且使用这些测量来确定双域电导。在第一遍中，在一组“紧密间隔”的电极上进行电位测量，并在迭代过程中使用双域模型和基于改进Shor‘s r算法的求解器将参数与电位测量值进行拟合。这第一个过程产生了细胞外电导。第二次是相似的，只是使用了一个“大间距”的电极组，这一次恢复了细胞内的电导率。此外，由于这里使用的比多曼模型能够包括纤维旋转的影响，因此可以确定整个组织中的纤维旋转。在这里给出的模拟研究中，用两个电极子集上的已知电导来求解该模型，以产生两组“测量的电位”。然后，通过求解基于测量的电势的反问题来恢复电导率，在该反问题上添加了不同级别的噪声。例如，对于纵向和横向空间常数分别为769和308微米的情况，使用500微米的电极间距来执行第一遍中的模拟。在添加了1%噪声的五次模拟中，纵向和横向胞外电导率的平均相对误差分别为0.3%和0.2%，非常准确。在1 mm网格上进行了25秒的模拟，对于相应的胞内值和纤维旋转角，分别产生了3.8、2.6和1.4%的平均百分比相对误差。
This paper describes a multi-electrode grid, which could be used to determine cardiac tissue parameters by direct measurement. A two pass process is used, where potential measurements are made, during the plateau phase of the action potential, on a subset of these electrodes and these measurements are used to determine the bidomain conductivities. In the first pass, the potential measurements are made on a set of 'closely-spaced' electrodes and the parameters are fitted to the potential measurements in an iterative process using a bidomain model and a solver based on a modified Shor's r-algorithm. This first pass yields the extracellular conductivities. The second pass is similar except that a 'widely-spaced' electrode set is used and this time the intracellular conductivities are recovered. In addition, it is possible to determine the fibre rotation throughout the tissue, since the bidomain model used here is able to include the effects of fibre rotation.In the simulation studies presented here, the model is solved with known conductivities, on each of the two subsets of electrodes, to generate two sets of 'measured potentials.' Conductivities are then recovered by solving an inverse problem based on the measured potentials, to which various levels of noise are added. For example, simulations in the first pass are performed using an electrode spacing of 500 mu m, for a situation where the longitudinal and transverse space constants are 769 and 308 mu m, respectively. These give very accurate average percentage relative errors for the longitudinal and transverse extracellular conductivities, over five simulations with 1% noise added, of 0.3 and 0.2%. Twenty-five second pass simulations, on a 1 mm grid, yield average percentage relative errors of 3.8, 2.6 and 1.4% for the corresponding intracellular values and the fibre rotation angle, respectively.