Modeling, measurement and prediction of cardiac magneto-stimulation thresholds

项目摘要/摘要 在磁共振成像中，心脏刺激(CS)是通过快速切换梯度对心脏的直接刺激 线圈，一种称为磁刺激的现象。美国联邦药品管理局(FDA) 对MRI中的梯度切换的速度和幅度施加了限制，但几乎 完全缺乏关于磁刺激的数据，这导致了必要的限制性安全 限制。取而代之的是，IEC 60601-2-33对磁共振成像中CS的限制，这是FDA依赖的限制，是 基于模拟人体躯干的均匀圆柱体中简化的电场计算，以及 使用电极在动物身上进行开胸CS实验。因为已知的限制 在这种方法中，IEC在选择CS限值时内置了较大的安全系数，从而导致 保守的安全建议。例如，中的四台西门子Connectome扫描仪 使用中，CS安全极限在长上升时间比周围神经刺激极限更具限制性， 这是不太可能的，因为心肌中的传导细胞比大细胞更难刺激 外周神经和心脏在身体的深处，因此更不受电的影响 田野胜过肤浅的神经。随着IEC MRI心脏刺激的安全限度越来越高 为了改善梯度系统，研究磁刺激是非常必要的。 使用直接的动物测量和最先进的技术更详细地研究这一现象 模拟方法。 据我们所知，只有两个小组发表了心脏磁力的直接测量- 20世纪90年代初，在狗身上进行了刺激。我们提出了一种多学科的生物工程 一项旨在首次测量心脏磁刺激的研究项目 猪的阈值，这是一种广泛使用的人类心血管系统动物模型。在……里面 此外，我们还开发了一个详细的心脏磁刺激模拟流水线。 最新的建模技术，以阐明CS的作用机制 并估计人体对各种线圈和梯度的刺激阈值 波形。我们将在以下期间与IEC的MT40小组委员会密切合作 为了确保我们的工作最大限度地为下一步IEC限制的设置提供信息 更新国际电工委员会60601-2-33标准。

Project Summary/Abstract In MRI, cardiac stimulation (CS) is the direct stimulation of the heart by rapid switching of the gradient coils, a phenomenon referred to as magneto-stimulation. The Federal Drug Administration (FDA) imposes limits on the speed and amplitude of gradient switching in MRI, however there is an almost complete lack of data on magneto-stimulation, which has resulted in a necessarily restrictive safety limit. Instead, the IEC 60601-2-33 limit for CS in MRI, which is the limit that the FDA relies on, is based on simplified electric field calculations in uniform cylinders that mimic the human torso, and open-chest CS experiments performed in animals using electrodes. Because of the known limitations of this methodology, the IEC built in large safety factors in their choice of the CS limit, thus resulting in a conservative safety recommendation. For example, for the four Siemens Connectome scanners in use, the CS safety limit is more restrictive than the peripheral nerve stimulation limit at long rise times, which is unlikely since conducting cells in the myocardium are harder to stimulate than large peripheral nerves and the heart is deep inside the body, and therefore more shielded from electric fields than shallow nerves. As the IEC MRI cardiac stimulation safety limit becomes more and more restrictive for improving gradient systems, it is essential to study the magneto-stimulation phenomenon in a more detailed manner using direct animal measurements and state-of-the-art simulation methods. To our knowledge, only two groups have published direct measurements of cardiac magneto- stimulation performed, in dogs, in the early 1990s. We propose a multidisciplinary bioengineering research project that aims to measure, for the first time, cardiac magneto-stimulation thresholds in pigs, a widely used animal model for the human cardiovascular system. In addition, we develop a detailed simulation pipeline of cardiac magneto-stimulation using state-of-the-art modeling techniques in order to shed light on the mechanisms of action of CS in MRI and estimate stimulation thresholds in humans for a variety of coils and gradient waveforms. We will work closely with the MT40 sub-committee of the IEC throughout the duration of the project in order to ensure that our work maximally informs the setting of the IEC limit in the next update of the IEC 60601-2-33 standard.