Ma Chao, Xu Dan, King Kevin F, Liang Zhi-Pei
Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Annu Int Conf IEEE Eng Med Biol Soc. 2009;2009:4064-6. doi: 10.1109/IEMBS.2009.5333196.
Design of RF pulses for parallel excitation using phased array transmit coils in MRI requires the B1+ maps that are estimated from B1+ mapping experiments. This paper characterizes the effects of B1+ mapping errors on the resulting excitation pattern using a small perturbation analysis based on linearization of the Bloch equation. The accuracy of the proposed perturbation analysis is validated by Bloch equation simulations based on experimental B1+ maps. The perturbation analysis builds a transparent connection between the B1+ mapping errors and the resulting excitation errors, and can be used to study the robustness of the designed RF pulses to B1+ mapping errors. The proposed method may also supply useful metrics for designing RF pulses that are robust to B1+ mapping errors.
在磁共振成像（MRI）中，使用相控阵发射线圈进行并行激发的射频（RF）脉冲设计需要通过B1 +映射实验估计的B1 +图。本文基于布洛赫方程的线性化，通过小扰动分析来表征B1 +映射误差对所得激发模式的影响。基于实验B1 +图的布洛赫方程模拟验证了所提出的扰动分析的准确性。扰动分析在B1 +映射误差与所得激发误差之间建立了清晰的联系，可用于研究设计的RF脉冲对B1 +映射误差的鲁棒性。所提出的方法还可为设计对B1 +映射误差具有鲁棒性的RF脉冲提供有用的指标。
