Pearce John A, Porterfield John E, Larson Erik R, Valvano Jonathan W, Feldman Marc D
Temple Foundation Professor of Electrical and Computer Engineering at the University of Texas at Austin, 1 University Station, TX 78712, USA.
Annu Int Conf IEEE Eng Med Biol Soc. 2010;2010:3556-8. doi: 10.1109/IEMBS.2010.5627712.
Cardiac volume estimation in the Left Ventricle from impedance or admittance measurement is subject to two major sources of error: parallel current pathways in surrounding tissues and a non uniform current density field. The accuracy of volume estimation can be enhanced by incorporating the complex electrical properties of myocardium to identify the muscle component in the measurement and by including the transient nature of the field non uniformity. Cardiac muscle is unique in that the permittivity is high enough at audio frequencies to make the muscle component of the signal identifiable in the imaginary part of an admittance measurement. The muscle contribution can thus be uniquely identified and removed from the combined muscle - blood measurement. In general, both error sources are transient and are best removed in real time as data are collected. This paper reviews error correction methods and establishes that the relative magnitudes of the error concerns are different in small and large hearts.
周围组织中的平行电流路径和不均匀的电流密度场。通过纳入心肌的复电特性以识别测量中的肌肉成分，并考虑场不均匀性的瞬态性质，可以提高容积估计的准确性。心肌的独特之处在于，在音频频率下其电容率足够高，使得信号的肌肉成分在导纳测量的虚部中可被识别。因此，可以唯一地识别肌肉贡献并从肌肉 - 血液联合测量中去除。一般来说，这两个误差来源都是瞬态的，最好在收集数据时实时去除。本文回顾了误差校正方法，并确定在小心脏和大心脏中，误差问题的相对大小是不同的。
