Clinical application of a biomagnetic measurement system with high temperature superconduction quantum interference device

1)用高温超导量子干涉仪(高T_c-SQUID)显示电流密度，评价心脏电流的可视化效果。使用32通道高T_c-SQUID(住友电气高能技术有限公司)测量心脏磁场。在一个被磁屏蔽的房间里。根据磁场梯度得到了32个导联点处的矢量电流，并构建了电流密度图。电流在去极化和复极化阶段都能清晰地检测到。以前，探测心脏磁场需要使用液氦的昂贵的鱿鱼系统。然而，该系统的特点是相对较高的成本效益和良好的空间分辨率。此外，对显示心脏电流密度的地图的研究还很少，这可能会提供有关电动势的重要信息。因此，该系统可用于临床…更广泛的应用是因为它便于检测详细的心脏电流。2)我们研究了利用心磁图的等磁图和电流密度图是否可以检测到由心电图无法推断的梗死向量。用二阶导数超导量子干涉仪(SQUID)记录陈旧性下壁心肌梗死患者(MI组)15例和正常健康人(N组)20例。根据相邻两点的磁场梯度计算出每36个胸前记录点的电流向量大小。对胸前电流分布进行样条插值，根据电流密度图估算心脏电动势。在N组所有受试者中，QRS波开始后30~40ms的QRS向量向左偏下，体表心电图或等磁图均不能识别多个偶极。此外，在N组的心室除极相电流密度图中，推导出一个电流密度。然而，与正常人不同的是，MI组的心室除极相的磁心图可以推断出多个电流密度。即Q波异常的下壁心肌患者，QRS波起搏后30~40ms的QRS向量在体表心电图上处于优势位置。非Q波下壁心肌梗死患者在等磁图上也可推断出上位QRS向量。MI组有4例体表心电图未检出多个电流源。这些结果提示，心室除极向量是由左、下向正常偶极子和下壁心肌梗死引起的异常上向偶极子组成的。结论：心磁图可以检测到心电图仪所不能推断的心梗电动势。较少

1)We evaluated whether the cardiac electrical current could be visualized by displaying the current density using a high temperature superconducting quantum interference device (high Tc-SQUID). Magnetic fields from heart were measured using a 32-channel high Tc-SQUID (Sumitomo Electric Hightecs, Co., Ltd.) in a magnetically shielded room. Vector currents were obtained at 32 lead points based on the magnetic gradient, and a current density map were constructed. Current electrical currents were clearly detected during depolarization and repolarization phases. Previously, the detection of magnetic field from the heart required an expensive SQUID system using liquid helium. However, this system was characterized-by its relative higher cost-effectiveness and excellent spatial resolution. In addition, few studies have been done on the map which displays cardiac current density, which can potentially provide important information on electromotive forces. Therefore, this system can be clinical … More ly applied because it facilitates the detection of detailed cardiac electrical current.2)We investigated whether an infarct vector that could not be deduced by electrocardiogram was detectable using isomagnetic and current density map of magnetocardiogram. Old inferior myocardial infarction (15 patients ; MI group) and normal healthy subjects (20 cases ; N group) were recorded with second derivative superconducting quantum interference device (SQUID) magnetocardiometer. Current vector magnitude of each 36 precordial recording point was calculated from magnetic field gradient of adjacent two points. Spline interpolation of precordial current distribution was performed and electromotive force of heart was estimated form current density map. In all subjects in the N group, the QRS vector at 30-40 msec after the onset of QRS wave was directed leftward and inferiorly and multiple dipoles could not be recognized from either surface electrocardiogram, or isomagnetic map. Moreover, in current density map of the ventricular depolarization phase in the N group, one current density was deduced. However, multiple current densities were deduced from the magnetocardiogram of the ventricular depolarization phase in the MI group unlike normal subject. That is, in inferior myocardial patient with abnormal Q wave, the QRS vector at 30-40 msec after the onset of QRS wave was directed superiorly in surface electrocardiogram. On the other hand, the superior QRS vector was deduced in isomagnetic map even in patients with non-Q wave inferior myocardial infarction. In the MI group, multiple current sources were suggested in 4 patients which did not be detected in body surface electrocardiogram. These results suggest that the ventricular depolarization vectors were composed of a normal dipole directed leftward and inferiorly, and an abnormal dipole directed superioly due to inferior myocardial infarction. It is concluded that magnetocardiogram can detect the infarct electromotive force which could not be deduced in electrocardiography. Less