Iterative correction of RF envelope distortion with GRATER-measured waveforms.
Iterative correction of RF envelope distortion with GRATER-measured waveforms.
复制标题
使用 GRATER 测量波形迭代校正 RF 包络失真。
DOI：
10.1002/mrm.27930
复制
发表时间：
2020
影响因子：
3.3
通讯作者：
Nayak,KrishnaS
中科院分区：
文献类型：
--
作者：
Landes,VanessaL;Nayak,KrishnaS
目的开发和评估一种无需额外硬件和同步的射频包络校正方法。方法通过一种简单的脉冲序列--梯度反转法来测量传输的射频波形以评估射频(Grater)。测量的射频波形被用来计算预失真的射频波形。重复该过程，直到例如基于脉冲性能或最大迭代次数满足停止标准。结果该方法提高了多频段射频脉冲的精度，将归一化均方根误差(NRMSE)降低了12倍，将虚假旁瓣激励降低了6倍。基于迭代栅格的预失真是一种实用的、不需要硬件的方法，可以提高短脉冲持续时间、低翻转角的RF脉冲的性能，例如用于短脉冲bSSFP成像的脉冲。由于其效率，该技术可作为初始扫描设置的一部分或用于后续扫描。
PurposeTo develop and evaluate a method for RF envelope correction without extra hardware or synchronization.MethodsTransmitted RF waveforms are measured through a simple pulse sequence called the gradient reversal approach to evaluate RF (GRATER). The measured RF waveforms are used to compute predistorted RF waveforms. This process is repeated until a stopping criterion is met, for example, based on pulse performance or a maximum number of iterations. Excitation profiles and simultaneous multi‐slice (SMS) image quality are compared before and after RF predistortion.ResultsThe proposed method improved the accuracy of multiband RF pulses, reducing normalized root mean squared error (NRMSE) by >12‐fold, and reducing spurious side‐lobe excitation by >6‐fold. The reduction in unwanted side‐lobe signal is demonstrated using SMS bSSFP imaging at 3T in phantoms and in the heart.ConclusionIterative GRATER‐based predistortion is a practical, hardware‐free way to boost performance of short duration, low flip angle RF pulses, such as those used in SMS bSSFP imaging. Because of its efficiency, this technique could be included as part of an initial scan setup or for use with subsequent scans.