使磁场梯度设计与磁体低温恒温器的几何形状相匹配。

Tailoring magnetic field gradient design to magnet cryostat geometry.

作者信息

Trakic A, Liu F, Lopez H S, Wang H, Crozier S

出版信息

Conf Proc IEEE Eng Med Biol Soc. 2006;2006:268-71. doi: 10.1109/IEMBS.2006.259223.

DOI:10.1109/IEMBS.2006.259223

Abstract

Eddy currents induced within a magnetic resonance imaging (MRI) cryostat bore during pulsing of gradient coils can be applied constructively together with the gradient currents that generate them, to obtain good quality gradient uniformities within a specified imaging volume over time. This can be achieved by simultaneously optimizing the spatial distribution and temporal pre-emphasis of the gradient coil current, to account for the spatial and temporal variation of the secondary magnetic fields due to the induced eddy currents. This method allows the tailored design of gradient coil/magnet configurations and consequent engineering trade-offs. To compute the transient eddy currents within a realistic cryostat vessel, a low-frequency finite-difference time-domain (FDTD) method using total-field scattered-field (TFSF) scheme has been performed and validated.

摘要

在梯度线圈脉冲期间，磁共振成像（MRI）低温恒温器腔内感应出的涡流可与产生它们的梯度电流相叠加，从而在规定的成像体积内随时间获得高质量的梯度均匀性。这可以通过同时优化梯度线圈电流的空间分布和时间预加重来实现，以考虑由于感应涡流引起的二次磁场的空间和时间变化。该方法允许对梯度线圈/磁体配置进行定制设计，并进行相应的工程权衡。为了计算实际低温恒温器容器内的瞬态涡流，已经执行并验证了一种使用全波散射场（TFSF）方案的低频有限差分时域（FDTD）方法。