de Alba Alvarez Irina, Arbabi Aidin, Khlebnikov Vitaliy, Marques José P, Norris David G
Donders Institute for Brain, Cognition and Behaviour, Centre for Cognitive Neuroimaging, Radboud University, Nijmegen, The Netherlands.
Multi-Modality Medical Imaging (M3I), Faculty of Science and Technology, University of Twente, Enschede, Netherlands.
Sci Rep. 2024 Apr 30;14(1):9949. doi: 10.1038/s41598-024-60275-4.
Measurements of frequency offset are commonly required in MRI. The standard method measures the signal phase as a function of evolution time. Here we use a single shot turbo-spin-echo acquisition method to measure frequency offset at a single evolution time. After excitation the transverse magnetisation evolves during the evolution time, and is then repeatedly refocused. The phase is conjugated between alternate echoes. Using partial parallel acquisition techniques we obtain separate odd- and even- echo images. An iterative procedure ensures self-consistency between them. The difference in phase between the two images yields frequency offset maps. The technique was implemented at 3 Tesla and tested on a healthy human volunteer for a range of evolution times between 6 and 42 ms. A standard method using a similar readout train and multiple evolution times was used as a gold-standard measure. In a statistical comparison with the gold standard no evidence for bias or offset was found. There was no systematic variation in precision or accuracy as a function of evolution time. We conclude that the presented approach represents a viable method for the rapid generation of frequency offset maps with a high image quality and minimal distortion.
在磁共振成像（MRI）中，通常需要测量频率偏移。标准方法是将信号相位作为演化时间的函数进行测量。在此，我们使用单次激发快速自旋回波采集方法在单个演化时间测量频率偏移。激发后，横向磁化在演化时间内演化，然后反复重聚。在交替回波之间相位共轭。使用部分并行采集技术，我们获得单独的奇数和偶数回波图像。迭代过程确保它们之间的自一致性。两幅图像之间的相位差产生频率偏移图。该技术在3特斯拉场强下实现，并在一名健康人类志愿者身上针对6至42毫秒范围内的一系列演化时间进行了测试。使用具有类似读出序列和多个演化时间的标准方法作为金标准测量。在与金标准的统计比较中，未发现偏差或偏移的证据。作为演化时间的函数，精度或准确性没有系统变化。我们得出结论，所提出的方法是一种可行的方法，可快速生成具有高图像质量和最小失真的频率偏移图。
