磁共振系统梯度线圈支撑结构的拓扑优化

Topology Optimization of Gradient Coil Support Structure of MRI System

磁共振(MRI)系统广泛应用于现代医疗影像诊断。其中梯度线圈是MRI系统的一个重要组成部分,其线圈效率以及产生梯度磁场的线性度直接影响到MRI系统的成像质量。在MRI系统工作时,通电的梯度线圈在MRI系统的匀强磁场中会受到洛伦兹力的作用,通过梯度线圈的脉冲电流,产生的洛伦兹力会导致线圈的变形和振动。所以对梯度线圈的支撑结构进行优化以提升梯度线圈在实际工作状态下的位置精度和稳定性对于成像精度有较为重要的作用。针对流函数方法设计的圆柱型梯度线圈的支撑结构,通过提高其刚度来降低洛伦兹力对梯度线圈精度的影响。使用基于密度法的多负载条件下SIMP拓扑优化方法,对x,y,z三个方向的梯度线圈支撑结构进行多负载条件下力学结构优化设计。得到较为符合受力状态的结构并且在实际工作状态下的性能得到了提高。

Magnetic Resonance Imaging(MRI)Systems are widely used in modern medical imaging diagnostics.The gradient coil is an important part of the MRI system,its efficiency and the linearity of the gradient magnetic field which it produces affect the imaging quality of the MRI system.When the MRI system works,the energized gradient coil is subjected to the Lorentz force in the uniform magnetic field of the MRI system,and as the current through the coil is pulsed,the Lorentz force will cause deformation and vibration of the coil.Therefore,the support structure of the gradient coil should be optimized in order to improve the mechanical properties of the gradient coil under actual working conditions.In this paper,the stiffness of the support structure of the cylindrical three-directional gradient coil designed with the stream function method was increased to reduce the influence of the Lorentz force on the accuracy of the gradient coil.The SIMP topology optimization method based on the density method under multi-load conditions was used to optimize the mechanical structure of the gradient coil support structure in three directions of x,y and z.The obtained results are in line with actual stress conditions and can be applied to actual products through various manufacturing methods.