. In this paper, an approach to the design of hemispherical breast RF coil array is proposed. The target field method is applied to find the current density distribution on the hemisphere surface, which induces a homo.... In this paper, an approach to the design of hemispherical breast RF coil array is proposed. The target field method is applied to find the current density distribution on the hemisphere surface, which induces a homogeneous magnetic field in a hemispherical volume. The components of current density are expanded into Fourier series, and the highly ill-conditioned character of the linear equation related to Fourier coefficients is solved using the Tikhonov regularization method with a minimum curvature penalty function. The winding pattern was acquired using the stream function technique. The results indicate that a simple winding pattern with homogeneous magnetic field can be obtained through manually selecting the penalty factor.展开更多
射频(RF)线圈是磁共振成像(MRI)系统的关键部件之一,用于射频信号的发射或接收,乳腺3 T MRI中采用专用的射频线圈可进一步提高磁共振成像的质量。为了获得简单的线圈绕线形状并使得射频磁场分布均匀,研究利用了L曲线自动选取和手动选取...射频(RF)线圈是磁共振成像(MRI)系统的关键部件之一,用于射频信号的发射或接收,乳腺3 T MRI中采用专用的射频线圈可进一步提高磁共振成像的质量。为了获得简单的线圈绕线形状并使得射频磁场分布均匀,研究利用了L曲线自动选取和手动选取惩罚因子对线圈绕线形状和磁场分布均匀性的影响,并结合目标场方法和流函数方法,提出了一种用于3 T(磁感应强度为3 T)乳腺磁共振成像的射频线圈设计方法。研究结果表明:1×1、2×1、2×2、4×1等4种半球形相控阵射频线圈的绕线形状随着阵列增加而变复杂;惩罚因子取利用L曲线自动选取的值时,磁感应强度线性方程的解最精确,阵列1×1在[10-25,10-18]区间内无论怎样选取惩罚因子,灵敏区内的磁场分布误差(即实际值与理想值之间的误差)都>40%,阵列2×2和4×1的磁场分布误差<10%,但是线圈绕线形状非常复杂,工程上难以实现;手动选取惩罚因子的值,可以使得磁场分布误差<40%,而且线圈的绕线形状简单;与相同半径和高度的圆柱型射频线圈相比,所提出的半球型射频线圈磁场分布更为均匀。可得结论:惩罚因子越小,则线圈绕线越复杂,而磁场分布越均匀;反之,惩罚因子越大,则线圈绕线越简单,而磁场分布越不理想。在简单的线圈绕线形状和保证射频磁场分布均匀之间取得平衡需要根据L曲线手动调节选取惩罚因子的值。展开更多
文摘. In this paper, an approach to the design of hemispherical breast RF coil array is proposed. The target field method is applied to find the current density distribution on the hemisphere surface, which induces a homogeneous magnetic field in a hemispherical volume. The components of current density are expanded into Fourier series, and the highly ill-conditioned character of the linear equation related to Fourier coefficients is solved using the Tikhonov regularization method with a minimum curvature penalty function. The winding pattern was acquired using the stream function technique. The results indicate that a simple winding pattern with homogeneous magnetic field can be obtained through manually selecting the penalty factor.
文摘射频(RF)线圈是磁共振成像(MRI)系统的关键部件之一,用于射频信号的发射或接收,乳腺3 T MRI中采用专用的射频线圈可进一步提高磁共振成像的质量。为了获得简单的线圈绕线形状并使得射频磁场分布均匀,研究利用了L曲线自动选取和手动选取惩罚因子对线圈绕线形状和磁场分布均匀性的影响,并结合目标场方法和流函数方法,提出了一种用于3 T(磁感应强度为3 T)乳腺磁共振成像的射频线圈设计方法。研究结果表明:1×1、2×1、2×2、4×1等4种半球形相控阵射频线圈的绕线形状随着阵列增加而变复杂;惩罚因子取利用L曲线自动选取的值时,磁感应强度线性方程的解最精确,阵列1×1在[10-25,10-18]区间内无论怎样选取惩罚因子,灵敏区内的磁场分布误差(即实际值与理想值之间的误差)都>40%,阵列2×2和4×1的磁场分布误差<10%,但是线圈绕线形状非常复杂,工程上难以实现;手动选取惩罚因子的值,可以使得磁场分布误差<40%,而且线圈的绕线形状简单;与相同半径和高度的圆柱型射频线圈相比,所提出的半球型射频线圈磁场分布更为均匀。可得结论:惩罚因子越小,则线圈绕线越复杂,而磁场分布越均匀;反之,惩罚因子越大,则线圈绕线越简单,而磁场分布越不理想。在简单的线圈绕线形状和保证射频磁场分布均匀之间取得平衡需要根据L曲线手动调节选取惩罚因子的值。
