Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China.
IEEE Trans Med Imaging. 2012 May;31(5):997-1007. doi: 10.1109/TMI.2011.2178035. Epub 2011 Dec 2.
Volume selective excitation has a variety of uses in clinical magnetic resonance imaging, but can suffer from insufficient excitation accuracy and impractically long pulse duration in ultra-high field applications. Based on recently-developed parallel transmission techniques, an optimized 3D tailored radio-frequency RF (TRF) pulse, designed with a novel 3D adaptive trajectory, is proposed to improve and accelerate volume selective excitation. The trajectory is designed to be regular-shaped and adaptively stretched according to the size of a 3D k-space "trajectory container." The container is designed to hold most of the RF energy deposition responsible for the desired pattern in the excitation k-space in the use of the blurring patterns caused by the multichannel sensitivity maps. The proposed method can also be used to reduce both global and peak RF energy required during excitation. The feasibility of this method is confirmed by simulations of ultra-high field cases.
体积选择性激发在临床磁共振成像中有多种用途，但在超高场应用中，激发准确性可能不足，且脉冲持续时间过长。基于最近开发的并行传输技术，提出了一种优化的 3D 定制射频（RF）脉冲，该脉冲采用新颖的 3D 自适应轨迹设计，以提高和加速体积选择性激发。该轨迹设计为规则形状，并根据 3D k 空间“轨迹容器”的大小自适应拉伸。容器的设计目的是在使用多通道灵敏度图引起的模糊图案时，在激发 k 空间中包含大部分负责所需图案的 RF 能量沉积。该方法还可用于减少激发过程中所需的全局和峰值 RF 能量。超高场案例的模拟证实了该方法的可行性。
