Spatial domain method for the design of RF pulses in multicoil parallel excitation
Spatial domain method for the design of RF pulses in multicoil parallel excitation
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DOI：
10.1002/mrm.20978
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发表时间：
2006-09-01
影响因子：
3.3
通讯作者：
Noll, Douglas C.
中科院分区：
文献类型：
--
作者：
Grissom, William;Yip, Chun-yu;Noll, Douglas C.
并行激励已经被引入作为使用多个发射线圈加速多维空间选择性激励的手段，每个发射线圈由独特的RF脉冲驱动。先前的并行激励中的RF脉冲设计方法或者在频域中制定，或者限于回波平面轨迹，或者两者兼而有之。本文提出了一种方法，制定为一个二次优化问题，在空间域中，并允许使用任意的k空间轨迹。与频域方法相比，新的设计方法具有一些重要的优点。它允许指定感兴趣区域（ROI），从而在高加速系数下提高激励精度。它允许在激励期间进行磁场不均匀性补偿。正则化可以用于控制积分和峰值脉冲功率。研究了Bloch方程非线性对该方法设计的射频脉冲大顶角激励误差的影响，并证明了Tikhonov正则化在减小该误差方面的实用性。
Parallel excitation has been introduced as a means of accelerating multidimensional, spatially-selective excitation using multiple transmit coils, each driven by a unique RF pulse. Previous approaches to RF pulse design in parallel excitation were either formulated in the frequency domain or restricted to echo-planar trajectories, or both. This paper presents an approach that is formulated as a quadratic optimization problem in the spatial domain and allows the use of arbitrary k-space trajectories. Compared to frequency domain approaches, the new design method has some important advantages. It allows for the specification of a region of interest (ROI), which improves excitation accuracy at high speedup factors. It allows for magnetic field inhomogeneity compensation during excitation. Regularization may be used to control integrated and peak pulse power. The effects of Bloch equation nonlinearity on the large-tip-angle excitation error of RF pulses designed with the method are investigated, and the utility of Tikhonov regularization in mitigating this error is demonstrated.