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

1)利用高温超导量子干涉装置（high Tc-SQUID）显示电流密度，评估心脏电流是否可以可视化。使用32通道Tc-SQUID （Sumitomo Electric Hightecs, Co., Ltd）在磁屏蔽室中测量心脏磁场。基于磁梯度得到32个导联点的矢量电流，构建电流密度图。在去极化和复极化阶段可以清楚地检测到电流。以前，从心脏探测磁场需要使用液氦的昂贵SQUID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进行的研究很少，这可能提供有关电动势的重要信息。因此，该系统便于对心脏电流的详细检测，具有较好的临床应用价值。2)我们研究了心肌磁图的等磁和电流密度图是否可以检测到心电图无法推断的梗死载体。用二阶导数超导量子干涉装置（SQUID）磁心仪记录老年性下壁心肌梗死15例（MI组）和正常健康人20例（N组）。根据相邻两点的磁场梯度计算每36个心前记录点的电流矢量大小。对心前电流分布进行样条插值，通过电流密度图估计心脏电动势。N组所有受试者在QRS波发生后30-40 msec的QRS矢量方向均为左下方向，无论是体表心电图还是等磁图均无法识别多个偶极子。在N组心室去极化期电流密度图中，推导出1个电流密度。然而，心肌梗死组与正常受试者不同，从心室去极化期的心磁图中可以推断出多重电流密度。即在Q波异常的下位心肌患者中，QRS波发生后30-40 msec的QRS矢量在体表心电图上指向优越。另一方面，即使在无q波的下位心肌梗死患者，在等磁图上也能推导出上位QRS矢量。心肌梗死组有4例患者体表心电图未检出多电流源。这些结果表明，心室去极化矢量由一个正常的向左和向下的偶极子组成，一个异常的向上的偶极子是由于下壁心肌梗死。结果表明，心磁图可以检测到心电图无法推断出的梗死灶电动势。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