Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
Magn Reson Med. 2013 Feb;69(2):503-8. doi: 10.1002/mrm.24259. Epub 2012 Apr 5.
The performance of multidimensional spatially selective radiofrequency (RF) pulses is often limited by their long duration. In this article, high-order, nonlinear gradients are exploited to reduce multidimensional RF pulse length. Specifically, by leveraging the multidimensional spatial dependence of second-order gradients, a two-dimensional spatial-spectral RF pulse is designed to achieve three-dimensional spatial selectivity, i.e., to excite a circular region-of-interest in a thin slice for reduced field-of-view imaging. Compared to conventional methods that use three-dimensional RF pulses and linear gradients, the proposed method requires only two-dimensional RF pulses, and thus can significantly shorten the RF pulses and/or improve excitation accuracy. The proposed method has been validated through Bloch equation simulations and phantom experiments on a commercial 3.0T MRI scanner.
多维空间选择性射频（RF）脉冲的性能通常受到其持续时间长的限制。本文利用高阶非线性梯度来缩短多维 RF 脉冲的长度。具体来说，通过利用二阶梯度的多维空间相关性，设计了一种二维空间-谱 RF 脉冲来实现三维空间选择性，即激励薄切片中的圆形感兴趣区域，以实现小视野成像。与使用三维 RF 脉冲和线性梯度的传统方法相比，该方法仅需要二维 RF 脉冲，因此可以显著缩短 RF 脉冲长度和/或提高激励准确性。该方法已通过 Bloch 方程模拟和商业 3.0T MRI 扫描仪上的体模实验进行了验证。
