Rabbani K S, Karal M A S
Biomedical Physics Laboratory, Department of Physics, University of Dhaka, Dhaka 1000, Bangladesh.
Ann Biomed Eng. 2008 Jun;36(6):1072-7. doi: 10.1007/s10439-008-9470-7. Epub 2008 Mar 18.
A recently developed Focused Impedance Measurement (FIM) system (by the authors' group) uses six electrodes to localize a zone of interest. Because of 3D sensitivity it could give physiological information on large organs like stomach, lungs, etc. using surface electrodes in the frontal plane. This paper presents a modified FIM technique using four electrodes placed at the corners of a square matrix. Firstly current is driven through an adjacent electrode pair while the potential is measured across the opposite pair from which an impedance value is obtained. Then a similar measurement is made at 90 degrees to the above by changing connections to the electrode pairs appropriately. The sum of these two impedance values has a dominant contribution from the central region within the square matrix, giving the desired focusing. Experimental sensitivity maps obtained from a 2D phantom have verified the focusing effect. Compared to the previous six-electrode FIM system the focusing effect is slightly less, but this new technique has less negative artifacts in the periphery. This new FIM method can be applied both in the frontal plane and in the transverse plane of the human thorax, giving a further advantage besides requiring fewer electrodes.
作者团队最近开发的聚焦阻抗测量（FIM）系统使用六个电极来定位感兴趣区域。由于其三维灵敏度，它可以通过额平面中的表面电极给出关于胃、肺等大器官的生理信息。本文提出了一种改进的FIM技术，使用四个放置在正方形矩阵角上的电极。首先，电流通过相邻的一对电极驱动，同时在相对的一对电极上测量电位，从中获得一个阻抗值。然后，通过适当地改变电极对的连接，在与上述方向成90度的方向上进行类似的测量。这两个阻抗值的总和在正方形矩阵内的中心区域有主要贡献，从而实现所需的聚焦。从二维模型获得的实验灵敏度图验证了聚焦效果。与之前的六电极FIM系统相比，聚焦效果略差，但这种新技术在外围的负伪影较少。这种新的FIM方法既可以应用于人体胸部的额平面，也可以应用于横平面，除了需要更少的电极外，还具有进一步的优势。
