Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD, Australia.
Australian Research Council Training Centre for Innovation in Biomedical Imaging Technology, The University of Queensland, Brisbane, QLD, Australia.
Sci Rep. 2020 Oct 23;10(1):18141. doi: 10.1038/s41598-020-74931-y.
Dynamically adjustable permanent magnet arrays have been proposed to generate switchable magnetic fields for pre-polarisation in Ultra-Low Field magnetic resonance imaging. However, the optimal switching dynamics of the pre-polarisation magnetic field as well as the energy requirements, mechanical forces and stresses during switching of the pre-polarisation field have not been evaluated. We analysed these requirements numerically and estimated the magnetic resonance signal strength and image quality for two practical switching modes in an instrument suitable for scanning the human head. Von Mises stress analysis showed that although magnetic forces were significantly higher for two specific rungs, the structural integrity of magnet rungs would not be compromised. Our simulations suggest that a significantly higher signal yield is obtained by switching off the pre-polarisation field with the angular velocity in each rung dependent on its location.
已经提出了动态可调永磁体阵列，以产生可切换磁场，用于超磁场磁共振成像中的预极化。然而，尚未评估预极化磁场的最佳切换动态以及预极化磁场切换期间的能量要求、机械力和应力。我们对这些要求进行了数值分析，并估计了适合扫描人头的仪器中的两种实际切换模式的磁共振信号强度和图像质量。冯·米塞斯（von Mises）应力分析表明，尽管两个特定梯级的磁力要高得多，但磁梯级的结构完整性不会受到影响。我们的模拟表明，通过以每个梯级的位置为依据，使其角速度依赖于其位置来关闭预极化磁场，可以获得更高的信号产量。
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