多腔体心脏磁场模型的研究与应用

利用核磁共振图像(MRI)中提取的人体和心脏边界,根据边界元方法(BEM)建立了一个考虑左、右心房和心室的多腔体心脏磁场模型.分析了用该模型得到的36通道心脏磁场数据和特定时刻的磁场图.并在此基础上,研究了完全性右束支传导阻滞(CRBBB)和完全性左束支传导阻滞(CLBBB)病人ST-T段的心脏电活动.结果显示,用移动单电流偶极子模拟的单束支电兴奋传导所产生的磁场图与用超导量子干涉器(SQUID)测量的CRBBB/CLBBB病人数据绘制的心脏复极时的心磁图(MCG)十分相似.结果表明,该多腔体心脏BEM模型可用于CLBBB/CRBBB病人心脏磁场逆问题的研究.此外,文中给出了两个评价指标:测量平面上多腔体与单腔体的心脏磁场强度极大值之比,以及两种模型的36个测量点上磁场强度均方根之比.分析表明,多腔体心脏模型更贴近人体心脏的实际情况.该模型中心脏组织电导率参数的取值,以及等效电流偶极子的位置和个数决定了磁场的强度和分布.

Research and application of multi-chamber heart magnetic field model

A multi-chamber heart magnetic field model with two atria and two ventricles, boundaries of which were picked up from a magnetic resonance imaging, was established based on the boundary element method (BEM). Moreover, the model-based 36-channel cardiac magnetic field data and magnetic field maps at a specific time were analyzed. We also studied the heart electrical activity during ST-T segment from patients with complete right bundle branch block (CRBBB) and complete left bundle branch block (CLBBB) by the model, respectively. Results show that the model-based magnetic field map generated by the electrical excitation with a moving single current dipole in single bundle branch is similar to the magnetocardiogram (MCG) of the CRBBB/CLBBB patient acquired using a superconducting quantum interference device (SQUID) in cardiac repolarization. It demonstrates that the multi-chamber heart BEM model can be used to study cardiac magnetic inverse problem of CLBBB/CRBBB patient. In addition, two evaluation criteria are given as follows: the ratio of the maximum on the magnetic field strength measurement plane in the multi-chamber model to that in the single-chamber model; and the ratio of root mean squares of the magnetic field strength at the 36 measurement points of the two models. This result indicates that the magnetic field maps generated by the multi-chamber heart model are close to the measured MCG maps. In this model, the strength and topography of the magnetic field lie in the conductivity parameters of cardiac tissues, the position and the number of the equivalent current dipoles.
Keywords： boundary element method (BEM) model magnetocardiography (MCG) cardiac electrical activity complete left/right bundle branch block (CLBBB/CRBBB)