COMPREHENSIVE ANALYSIS OF LENZ EFFECT ON THE ARTIFICIAL HEART VALVES DURING MAGNETIC RESONANCE IMAGING
COMPREHENSIVE ANALYSIS OF LENZ EFFECT ON THE ARTIFICIAL HEART VALVES DURING MAGNETIC RESONANCE IMAGING
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DOI：
10.2528/pier12031505
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发表时间：
2012-01-01
影响因子：
6.7
通讯作者：
Graham, S. J.
中科院分区：
文献类型：
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作者：
Golestanirad, L.;Dlala, E.;Graham, S. J.
这项工作提出了一个全面的分析结果的伦茨效应，由于人工心脏瓣膜的运动在磁共振成像。通过对相应的电磁问题进行时域分析，研究了旋转金属心脏瓣膜与磁场的相互作用。我们应用有限元法（FEM）求解了两种情况下的麦克斯韦方程的T - Omega公式：第一种情况是金属盘位于磁体等中心的高强度均匀磁场中，第二种情况是金属盘位于孔入口的非均匀边缘场中。我们证明，对于位于磁体等中心的全实心圆盘（如Starr-Edwards 6500）瓣膜，不利力的大小可与跳动心脏施加的力相当。然而，对于由多个连接的导电区域组成的环，趋肤效应和邻近效应抵消，这导致磁力减小。本研究的结果表明，即使在场强高达10 T的超高成像条件下，带加强环的机械心脏瓣膜也可以被认为是安全的。然而，具有全传导盘的心脏瓣膜应被视为MR成像的禁忌症。
This work presents results of a comprehensive analysis of the Lenz effect due to motion of artificial heart valves during magnetic resonance imaging. The interaction of rotating metallic heart valves with magnetic fields is studied by performing a time-domain analysis of the corresponding electromagnetic problem. We applied the finite element method (FEM) to solve the T - Omega formulation of Maxwell equations in two cases: first, for metallic disks located in the high intensity homogenous field of the magnet iso-center, and second, disks located in the non-uniform fringe field of the bore entrance. We showed that for valves with full solid disks (such as Starr-Edwards 6500) located in the magnet iso-center, the magnitude of adverse forces can be comparable to the forces applied by the beating heart. However, for rings which consist of multiply connected conductive regions, skin effect and proximity effect counteract, which leads to a diminished magnetic force. Results of this study show that mechanical heart valves with strengthening rings may be considered safe even under ultra-high imaging conditions with field intensities as high as 10 T. However, heart valves with full conducting disks should be considered as a contraindication to MR imaging.