Jang Albert, Kobayashi Naoharu, Moeller Steen, Vaughan J Thomas, Zhang Jianyi, Garwood Michael
Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minnesota, USA.
Department of Electrical and Computer Engineering, University of Minnesota, Minnesota, USA.
Magn Reson Med. 2016 Nov;76(5):1364-1374. doi: 10.1002/mrm.25973. Epub 2015 Nov 27.
To introduce a method of designing two-dimensional (2D) frequency-modulated pulses that produce phase coherence in a spatiotemporal manner. Uniquely, this class of pulses provides the ability to compensate for field inhomogeneity using a spatiotemporally dependent trajectory of maximum coherence in a single-shot.
A pulse design method based on a k-space description is developed. Bloch simulations and phantom experiments are used to demonstrate sequential spatiotemporal phase coherence and compensation for B1+ and B inhomogeneity.
In the presence of modulated gradients, the 2D frequency-modulated pulses were shown to excite a cylinder in a selective manner. With a surface coil transmitter, compensation of the effect of B1+ inhomogeneity was experimentally verified, in agreement with simulation results. In addition, simulations were used to demonstrate partial compensation for B inhomogeneity.
The 2D frequency-modulated pulses are a new class of pulses that generate phase coherence sequentially along a spatial trajectory determined by gradient- and frequency-modulated functions. By exploiting their spatiotemporal nature, 2D frequency-modulated pulses can compensate for spatial variation of the radiofrequency field in a single-shot excitation. Preliminary results shown suggest extensions might also be used to compensate for static field inhomogeneity. Magn Reson Med 76:1364-1374, 2016. © 2015 International Society for Magnetic Resonance in Medicine.
介绍一种设计二维（2D）调频脉冲的方法，该方法能以时空方式产生相位相干性。独特的是，这类脉冲能够在单次激发中利用最大相干性的时空相关轨迹来补偿场不均匀性。
开发了一种基于k空间描述的脉冲设计方法。使用布洛赫模拟和体模实验来证明顺序时空相位相干性以及对B1 +和B不均匀性的补偿。
在存在调制梯度的情况下，二维调频脉冲被证明能够以选择性方式激发圆柱体。使用表面线圈发射器，通过实验验证了对B1 +不均匀性影响的补偿，与模拟结果一致。此外，模拟用于证明对B不均匀性的部分补偿。
二维调频脉冲是一类新型脉冲，它们沿着由梯度和频率调制函数确定的空间轨迹顺序产生相位相干性。通过利用其时空特性，二维调频脉冲可以在单次激发中补偿射频场的空间变化。所示的初步结果表明，其扩展应用可能还可用于补偿静磁场不均匀性。《磁共振医学》76:1364 - 1374, 2016。© 2015国际磁共振医学学会。
