Vanderbilt University Institute of Imaging Science, Vanderbilt University, 1161 21st Ave. South, Nashville, TN 37232, USA.
J Magn Reson. 2010 Apr;203(2):294-304. doi: 10.1016/j.jmr.2010.01.012. Epub 2010 Feb 4.
Sparse-spokes pulses are 2D slice-selective pulses that effectively mitigate inhomogeneities in the transmitted RF field and reduce unwanted RF artifacts in MR images. Here we consider the practical design of such pulses for high-field MRI and demonstrate limitations of the technique. We analyze the performance of pulses considering input noise as well as other effects such as saturation and T2( *) relaxation. We discuss in detail the correspondence between the reduction of RF inhomogeneities and the fidelity of the input parameters, such as the transmit B1+ field map and combined phase of the main B0 field and eddy-currents. Results include simulations, utilizing 7 T field maps acquired in phantoms and in-vivo, as well as in-vivo experiments. The necessary performance of system hardware components to achieve significant improvements is described.
稀疏 spokes脉冲是二维切片选择性脉冲，可有效减轻发射 RF 场中的不均匀性，并减少磁共振图像中的不必要的 RF 伪影。在这里，我们考虑了这种用于高场 MRI 的实用设计，并展示了该技术的局限性。我们分析了考虑输入噪声以及饱和和 T2（*）弛豫等其他效应的情况下脉冲的性能。我们详细讨论了减少 RF 不均匀性与输入参数（例如发射 B1 + 场图以及主 B0 场和涡流的组合相位）的保真度之间的对应关系。结果包括利用在体模和体内获得的 7 T 场图以及体内实验进行的模拟。描述了实现显著改进所需的系统硬件组件的性能。
