Composite RF pulses for B1+-insensitive volume excitation at 7 Tesla
Composite RF pulses for B1+-insensitive volume excitation at 7 Tesla
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DOI：
10.1016/j.jmr.2010.04.002
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发表时间：
2010-07-01
影响因子：
2.2
通讯作者：
Gore, John C.
中科院分区：
文献类型：
--
作者：
Moore, Jay;Jankiewicz, Marcin;Gore, John C.
一种新型复合射频脉冲，在特定范围的B-0和B-1（+）不均匀性中表现良好，已被设计用于MRI的体积（非选择性）激发。脉冲由许多（大约100个）短的（大约10 μ s）块状子脉冲组成，每个子脉冲具有不同的相位和振幅，这些脉冲是由数值优化得出的。优化的脉冲被设计为在特定的频率偏移和发射场变化范围内有效，因此无论场强、发射线圈配置或静态和射频场的特定空间分布如何，都可以实现。在7t人脑成像的背景下，仿真和模拟实验都表明，优化后的脉冲与BIR-4脉冲具有相似的非共振翻转角均匀性，但具有优越的非共振稳定性和显著降低的平均功率。因此，本文提出的脉冲设计技术非常适合于超高场人体MRI的实际应用。(C) 2010爱思唯尔公司版权所有。
A new class of composite RF pulses that perform well in the presence of specific ranges of B-0 and B-1(+) inhomogeneities has been designed for volume (non-selective) excitation in MRI. The pulses consist of numerous (similar to 100) short (similar to 10 mu s) block-shaped sub-pulses each with different phases and amplitudes derived from numerical optimization. Optimized pulses are designed to be effective over a specific range of frequency offsets and transmit field variations and are thus implementable regardless of field strength, transmit coil configuration, or the subject-specific spatial distribution of the static and RF fields. In the context of 7 T human brain imaging, both simulations and phantom experiments indicate that optimized pulses result in similar on-resonance flip-angle uniformity as BIR-4 pulses but with the advantages of superior off-resonance stability and significantly reduced average power. The pulse design techniques presented here are thus well-suited for practical application in ultra-high field human MRI. (C) 2010 Elsevier Inc. All rights reserved.