Roemer Peter B, Rutt Brian K
Roemer Consulting, Lutz, Florida, USA.
Department of Radiology, Stanford University, Stanford, California, USA.
Magn Reson Med. 2021 Jul;86(1):569-580. doi: 10.1002/mrm.28681. Epub 2021 Feb 9.
To develop new concepts for minimum electric-field (E-field) gradient design, and to define the extents to which E-field can be reduced in gradient design while maintaining a desired imaging performance.
Efficient calculation of induced electric field in simplified patient models was integrated into gradient design software, allowing constraints to be placed on the peak E-field. Gradient coils confined to various build envelopes were designed with minimum E-fields subject to standard magnetic field constraints. We examined the characteristics of E-field-constrained gradients designed for imaging the head and body and the importance of asymmetry and concomitant fields in achieving these solutions.
For transverse gradients, symmetric solutions create high levels of E-fields in the shoulder region, while fully asymmetric solutions create high E-fields on the top of the head. Partially asymmetric solutions result in the lowest E-fields, balanced between shoulders and head and resulting in factors of 1.8 to 2.8 reduction in E-field for x-gradient and y-gradient coils, respectively, when compared with the symmetric designs of identical gradient distortion.
We introduce a generalized method for minimum E-field gradient design and define the theoretical limits of magnetic energy and peak E-field for gradient coils of arbitrary cylindrical geometry.
开发最小电场（E场）梯度设计的新概念，并确定在保持所需成像性能的同时，梯度设计中E场可降低的程度。
将简化患者模型中感应电场的高效计算集成到梯度设计软件中，从而能够对峰值E场施加约束。在标准磁场约束条件下，设计了限制在各种结构包络内的梯度线圈，使其具有最小E场。我们研究了为头部和身体成像而设计的E场约束梯度的特性，以及不对称性和伴随场在实现这些解决方案中的重要性。
对于横向梯度，对称解决方案在肩部区域产生高水平的E场，而完全不对称解决方案在头顶产生高E场。部分不对称解决方案产生的E场最低，在肩部和头部之间达到平衡，与具有相同梯度失真的对称设计相比，x梯度和y梯度线圈的E场分别降低了1.8至2.8倍。
我们引入了一种最小E场梯度设计的通用方法，并定义了任意圆柱形几何形状梯度线圈的磁能和峰值E场的理论极限。
