Skinner Thomas E, Kobzar Kyryl, Luy Burkhard, Bendall M Robin, Bermel Wolfgang, Khaneja Navin, Glaser Steffen J
Physics Department, Wright State University, Dayton, OH 45435, USA.
J Magn Reson. 2006 Apr;179(2):241-9. doi: 10.1016/j.jmr.2005.12.010. Epub 2006 Jan 18.
An optimal control algorithm for generating purely phase-modulated pulses is derived. The methodology is applied to obtain broadband excitation with unprecedented tolerance to RF inhomogeneity. Design criteria were transformation of Iz-->Ix over resonance offsets of +/-25 kHz for constant RF amplitude anywhere in the range 10-20 kHz, with a pulse length of 1 ms. Simulations transform Iz to greater than 0.99 Ix over the targetted ranges of resonance offset and RF variability. Phase deviations in the final magnetization are less than 2-3 degrees over almost the entire range, with sporadic deviations of 6-9 degrees at a few offsets for the lowest RF (10 kHz) in the optimized range. Experimental performance of the new pulse is in excellent agreement with the simulations, and the robustness of the excitation pulse and a derived refocusing pulse are demonstrated by insertion into conventional HSQC and HMBC-type experiments.
推导了一种用于生成纯相位调制脉冲的最优控制算法。该方法被应用于获得对射频不均匀性具有前所未有的耐受性的宽带激发。设计标准是在10 - 20 kHz范围内的任何恒定射频幅度下，在+/-25 kHz的共振偏移上实现Iz到Ix的转换，脉冲长度为1 ms。模拟结果表明，在目标共振偏移和射频变化范围内，Iz转换为大于0.99 Ix。最终磁化强度的相位偏差在几乎整个范围内小于2 - 3度，在优化范围内最低射频（10 kHz）的几个偏移处偶尔有6 - 9度的偏差。新脉冲的实验性能与模拟结果非常吻合，并且通过将激发脉冲和推导的重聚焦脉冲插入传统的HSQC和HMBC型实验中，证明了激发脉冲和重聚焦脉冲的稳健性。
