Bradshaw L A, Richards W O, Wikswo J P
Department of Physics & Astronomy, Vanderbilt University, Nashville, Tennessee, USA.
Med Biol Eng Comput. 2001 Jan;39(1):35-43. doi: 10.1007/BF02345264.
An analysis of the relative capabilities of methods for magnetic and electric detection of gastrointestinal electrical activity is presented. The model employed is the first volume conductor model for magnetic fields from GEA to appear in the literature. A mathematical model is introduced for the electric potential and magnetic field from intestinal electrical activity in terms of the spatial filters that relate the bioelectric sources with the external magnetic fields and potentials. The forward spatial filters are low-pass functions of spatial frequency, so more superficial external fields and potentials contain less spatial information than fields and potentials near the source. Inverse spatial filters, which are reciprocals of the forward filters, are high-pass functions and must be regularised by windowing. Because of the conductivity discontinuities introduced by low-conductivity fat layers in the abdomen, the electric potentials recorded outside these layers required more regularisation than the magnetic fields, and thus, the spatial resolution of the magnetic fields from intestinal electrical activity is higher than the spatial resolution of the external potentials. In this study, two smooth muscle sources separated by 5cm were adequately resolved magnetically, but not resolved electrically. Thus, sources are more accurately localized and imaged using magnetic measurements than using measurements of electric potential.
本文对胃肠道电活动的磁检测和电检测方法的相对能力进行了分析。所采用的模型是文献中首次出现的用于胃肠道电活动磁场的第一体积导体模型。引入了一个数学模型，根据将生物电源与外部磁场和电位相关联的空间滤波器，来描述肠道电活动产生的电势和磁场。正向空间滤波器是空间频率的低通函数，因此，与源附近的场和电位相比，更浅表的外部场和电位包含的空间信息更少。反向空间滤波器是正向滤波器的倒数，是高通函数，必须通过加窗进行正则化。由于腹部低导电脂肪层引入的电导率不连续性，这些层外部记录的电势比磁场需要更多的正则化，因此，肠道电活动磁场的空间分辨率高于外部电位的空间分辨率。在本研究中，两个相距5cm的平滑肌源通过磁检测能够得到充分分辨，但电检测无法分辨。因此，与使用电位测量相比，使用磁测量能够更准确地对源进行定位和成像。
