Joint Design of Spoke Trajectories and RF Pulses for Parallel Excitation
Joint Design of Spoke Trajectories and RF Pulses for Parallel Excitation
复制标题
DOI：
10.1002/mrm.22676
复制
发表时间：
2011-04-01
影响因子：
3.3
通讯作者：
Liang, Zhi-Pei
中科院分区：
文献类型：
--
作者：
Ma, Chao;Xu, Dan;Liang, Zhi-Pei
辐条轨迹通常用于设计需要薄片选择和片内调制的多维射频脉冲。理想情况下，需要一组覆盖整个k空间的辐条来产生给定的激励模式。然而，在实践中，由于射频脉冲长度的限制，只能使用少量辐条。因此，辐条位置对产生的射频脉冲的性能至关重要，原则上应根据给定的激励模式和发射灵敏度与射频脉冲共同优化。在这项工作中，我们将关节设计问题表述为基于小尖角射频脉冲设计的最优辐选择问题。提出了一种基于序列选择的递归代价函数评估算法，以寻求最优辐条位置，使激励误差最小。在配备双通道并联励磁系统的3特斯拉扫描仪上进行的Bloch方程仿真和实验结果表明，该方法产生的励磁误差明显小于传统方法，且计算效率高。中华医学杂志（英文版），2011。(C) 2010 Wiley-Liss, Inc。
The spoke trajectory is often used in designing multidimensional RF pulses for applications requiring thin slice selection and in-slice modulation. Ideally, a full set of spokes covering the whole k-space are desired to generate a given excitation pattern. In practice, however, only a small number of spokes can be used due to the RF pulse length limitation. The spoke locations are, therefore, critical to the performance of the resulting RF pulse and should be in principle optimized jointly with the RF pulse for a given excitation pattern and transmit sensitivities. In this work, we formulate the joint design problem as an optimal spoke selection problem based on the small-tip-angle RF pulse design. A sequential selection based algorithm with recursive cost function evaluation is proposed to seek optimized spoke locations to minimize the excitation error. Bloch equation simulations and experimental results on a 3 Tesla scanner equipped with a two-channel parallel excitation system demonstrate that the proposed method can produce significantly smaller excitation error than conventional methods with high computational efficiency. Magn Reson Med 65:973-985, 2011. (C) 2010 Wiley-Liss, Inc.